Understanding Our Bodies – nutritionwonderland

Understanding Our Bodies – Fiber!

nutrition — Mon, 24 May 2010 08:37:42 +0000

ost of us already know that we should be eating fiber – according to the Institute of Medicine, adults should be eating 20-35 grams of it per day. But why? What’s so important about fiber anyway? What does it do for us physiologically? And does it matter what kind of fiber we eat?

I can hear some of you now – wait, there’s more than one kind of fiber? Yes, there is, though you won’t see it detailed on any nutritional label. Most of the time, we’re told to simply focus on total fiber , no matter where it comes from. While getting enough total fiber is key, getting enough of each kind of fiber may be just as important in having a healthy, happy digestive system.

What is Fiber? And what does it do?

Peas, an excellent source of fiber – thanks to Sami Taipale flickr

Fiber is similar to starches and sugars in that it’s mostly made of carbohydrates . The difference is that fiber refers to the carbohydrates that your body can’t digest, while starches and sugars are carbohydrates that humans easily digest. Why would we want to eat something our bodies don’t digest? As it turns out, even though we can’t digest it, fiber helps us digest other things and keeps our digestive system running smoothly. Of course, the kind of fiber matters.

There are two main categories of fiber: soluble and insoluble. Soluble fiber dissolves in water, while insoluble fiber, as the name suggests, doesn’t. The average American fiber intake contains 75% insoluble fiber and 25% soluble fiber, each having its own special physiological impacts on digestion.

Insoluble fiber, like the fiber in whole wheat foods, bran, nuts, and seeds, mostly helps by simply being there. It’s what forms the mass that moves through your bowels, and while that might sound a little gross, it’s key to preventing conditions like diarrhea and constipation. Because it stays in a solid form, it helps compact the forming stool, which allows it to move more easily through the intestines. Some health professionals also believe that insoluble fiber acts like a sponge or scrub brush, cleaning the digestive tract as it goes along by gently scraping the walls and snowballing with stray particles so they are removed from the body.

Flax – soluable fiber city! credit: alishaV, flickr

Soluble fiber, found in fruits, vegetable and flax seed, acts differently because it becomes gel-like in water, actually incorporating with liquids. Soluble fiber helps hydrate stool, allowing it to slip though the intestines smoothly, a key in preventing digestive disorders. But soluble fiber does so much more – often called “viscous fiber“, soluble fiber makes your digestive contents into a thick slurry, which slows down your digestive system, slowing the process of absorption in the small intestine.

The effect of this is that you feel fuller, longer, because of slower, steadier increases in blood glucose levels, and your body requires less food to attain the same absorption of energy and nutrients. One study found that adding one kind of soluble fiber to their subject’s diets reduced the their food intake by 11%!

But soluble fiber also helps regulate the levels of glucose in our blood more directly. Soluble fiber is often fermented during our digestive processes, producing compounds called short-chain fatty acids and gasses (FYI, this is where increases in flatulence can come from when eating beans – legumes are high in soluble fiber and fructo-oligo-saccharides).

Short-chain fatty acids have a number of physiological roles. These small fat molecules have been shown to directly influence insulin release from the pancreas and glycogen breakdown in the liver, leading to stable and healthy glucose levels. Short-chain fatty acids also influence the liver’s production of cholesterol. The effect of this is that increased fiber consumption lowers the circulating bad cholesterol in the blood. They’ve been found to promote the production of immune cells and antibodies, potentially boosting immune function. Furthermore, these little acids help regulate the pH (acidity) of the intestines and the colon, keeping it in the right range to promote nutrient absorption and discourage microbes from producing toxins and carcinogenic substances.

A good video review of this information can be found here:

Fiber and Disease

Mega Burgers, not so hot on fiber – credit, marshall astor

The old adage “an apple a day keeps the doctor away” may be more true than we thought. Apples are great sources of fiber, and both soluble and insoluble fibers help reduce the risk of a variety of diseases. One of the most well understood is fiber’s connection to diabetes. Because fiber slows down your digestive system, glucose enters your bloodstream at slower, more stable rate, and this helps with managing Type 1 diabetes. But fiber can help prevent Type 2 diabetes, too.

Type 2 diabetes can be induced by our diets when our bodies are exposed to high blood glucose levels for a long period of time. This can happen because of consistent over-intake of sugars and carbohydrates, but it can also occur because our bodies are unable to produce enough insulin to lower rising blood sugar levels, or we become desensitized to insulin activity. By creating a slow, steady stream of glucose uptake, fiber helps our bodies avoid the sudden spikes glucose and insulin that, over time, can lead to Type 2 diabetes.

Studies have shown that diets high in fiber reduce the risk of Type 2 diabetes significantly. For example, a meta-analysis of several large studies (totaling to over 700,000 people) found that eating an additional 2 servings of whole grains a day decreased the risk of Type 2 diabetes by 21%. Both soluble and insoluble fiber intake are correlated with reduced diabetes risk, though how the insoluble fiber is involved is less understood.

Fiber is also strongly linked to reducing risk of heart disease. This is likely due to its positive influence on blood cholesterol levels. A number of large, long-term studies have found that people with high-fiber diets have up to a 40% lower risk of coronary heart disease.

Furthermore, a meta-analysis of seven large studies found that the risk of developing cardiovascular disease was 21% lower in people who ate 2.5 or more servings of whole grain foods a day compared with those who ate much less. Mostly, these studies suggest that soluble fiber is the key player in preventing cardiovascular problems. Because of the extensive, strong correlation between soluble fiber intake and lowered risk, soluble fiber is one of the very few things that the FDA officially recognizes as reducing the risk of heart disease.

Furthermore, a recent study has found that increasing soluble fiber intake, but not insoluble fiber intake, actually helps boost our immune systems. Mice were fed low-fat diets that either contained regular amounts of soluble or insoluble fiber for six weeks before being subjected to an agent that mimics a bacterial infection. When the two groups were compared, the soluble-fiber eating mice were only half as sick as their insoluble-eating counterparts, and they recovered 50% sooner. What made the soluble fiber so much better for the mice?

Scientists discovered that the soluble fiber-eating mice were producing higher levels of anti-inflammatory compounds, perhaps due to short-chain fatty acids. Immune cells in our bodies have to deal with both invaders like infections and self-caused problems like inflammation. The researchers believe that by reducing the inflammation response, ingesting soluble fiber altered the mice’s immune cells, making them switch from problematic inflammatory cells to anti-inflammatory cells that can deal with other problems, like the faked infection. While this research is preliminary, it’s impressive that the mice immune systems were altered by manageable amounts of fiber that could easily be eaten by people.

The one thing fiber intake doesn’t help much with, though, is the one disease it’s most often touted as a way of preventing: colon cancer. The truth is that the connection between dietary fiber and reduced risk of developing colon cancer is weak at best. While some smaller studies have linked high-fiber diets to lowered risk of colon cancer, larger ones, like a 16-year Harvard study of more than 80,000 nurses, have found no connection.

Take Home Message: EAT MORE FIBER!

The scientific evidence is unmistakable – fiber is vital for a healthy digestive system. More often than not, you’ll be told to simply eat more fiber, but from the evidence I’ve seen, you should be particularly eating more soluble fiber. And that isn’t the kind of fiber normally touted – often, you hear people push for whole grains, which are good sources of insoluble fiber, even though it’s soluble fiber that is much more strongly linked to fiber’s various health benefits. There’s another problem, too – according to nutrition labels, fiber is fiber. There is no distinction between soluble and insoluble fiber in packaged foods. Instead, you have to be your own nutrition expert, and know which fiber-filled foods are naturally high in soluble fiber. Here are a few good ones:

Foodstuff	Serving Size	Total Fiber (g)	Soluble Fiber	Insoluble Fiber (g)
Grapefruit	1/2 fruit	1.3	0.9	0.4
Squash, summer	1/2 cup	2.3	1.1	1.2
Zucchini	1/2 cup	2.5	1.1	1.4
Brown rice	1/2 cup	1.3	1.3	0
Rolled Oats	3/4 cup	3	1.3	1.7
Orange	1 medium	2	1.3	0.7
Plums	2 medium	2.3	1.3	1
Broccoli	1 stalk	2.7	1.3	1.4
Carrots	1 large	2.9	1.3	1.6
Tangerine	1 medium	1.6	1.4	0.4
Peas	1/2 cup	5.2	2	3.2
Pinto beans	1/2 cup	3	2.2	0.7
Potatoes	1 small	3.8	2.2	1.6
Apple	1 small	3.9	2.3	1.6
Psyllium husk	10g	8	7.1	0.9

Of course, no matter what you should probably be eating more fiber. Studies have found that Americans eat 50% or less than the recommended intake every day! So while soluble fiber may be the best option, any fiber is a start!

What are the downsides to eating fiber? After all, it sounds so wonderful – there must be something bad about it, right? Well… there is the gas produced by soluble fiber fermentation, but that seems a small price to pay compared to the many benefits that fiber intake can have. Sorry to sound unbelievable, but no, in my opinion, there aren’t any real downsides. Actually, I’ll rephrase – there aren’t any downsides to eating the amount of fiber you get from the kinds of foods people eat, so long as you still get the necessary amounts of protein and other nutrients, too. Switch to eating entirely fiber-rich grasses instead of the normal grains, fruits and veggies and you might not fare so well. The only thing I will recommend, though, is that if you plan on dramatically increasing your dietary fiber intake, do it somewhat slowly to allow your body to adjust to the rise in non-digestible material in your diet. This will help you prevent the only known clinical side effects of sudden, high-fiber intake – tummy trouble.

Previous posts in the Understanding Our Bodies series:

Citations:

Leathwood P, & Pollet P (1988). Effects of slow release carbohydrates in the form of bean flakes on the evolution of hunger and satiety in man. Appetite, 10 (1), 1-11 PMID: 3355122

Ruottinen S, Lagström HK, Niinikoski H, Rönnemaa T, Saarinen M, Pahkala KA, Hakanen M, Viikari JS, & Simell O (2010). Dietary fiber does not displace energy but is associated with decreased serum cholesterol concentrations in healthy children. The American journal of clinical nutrition, 91 (3), 651-61 PMID: 20071642

de Mello VD, & Laaksonen DE (2009). [Dietary fibers: current trends and health benefits in the metabolic syndrome and type 2 diabetes] Arquivos brasileiros de endocrinologia e metabologia, 53 (5), 509-18 PMID: 19768242

de Munter, J., Hu, F., Spiegelman, D., Franz, M., & van Dam, R. (2007). Whole Grain, Bran, and Germ Intake and Risk of Type 2 Diabetes: A Prospective Cohort Study and Systematic Review PLoS Medicine, 4 (8) DOI: 10.1371/journal.pmed.0040261

Pereira, M. (2004). Dietary Fiber and Risk of Coronary Heart Disease: A Pooled Analysis of Cohort Studies Archives of Internal Medicine, 164 (4), 370-376 DOI: 10.1001/archinte.164.4.370

Rimm, E. (1996). Vegetable, fruit, and cereal fiber intake and risk of coronary heart disease among men JAMA: The Journal of the American Medical Association, 275 (6), 447-451 DOI: 10.1001/jama.275.6.447

Brown L, Rosner B, Willett WW, & Sacks FM (1999). Cholesterol-lowering effects of dietary fiber: a meta-analysis. The American journal of clinical nutrition, 69 (1), 30-42 PMID: 9925120

MELLEN, P., WALSH, T., & HERRINGTON, D. (2008). Whole grain intake and cardiovascular disease: A meta-analysis Nutrition, Metabolism and Cardiovascular Diseases, 18 (4), 283-290 DOI: 10.1016/j.numecd.2006.12.008

Fuchs, C. (1999). Dietary Fiber and the Risk of Colorectal Cancer and Adenoma in Women New England Journal of Medicine, 340 (3), 169-176 DOI: 10.1056/NEJM199901213400301

Understanding Our Bodies: Insulin

nutrition — Thu, 13 May 2010 07:30:58 +0000

Almost everyone has heard of Insulin. You probably know that people with type 1 diabetes need to inject themselves with insulin to survive, and must constantly monitor the amount of sugar they eat. But what do you really know about insulin? What is its purpose in the body, and why do we need it? How does it relate to our diets? What happens when things go wrong with it? And why should anyone who doesn’t have diabetes give a hoot?

Insulin is one of the most important hormones in the human body, and yet most people don’t really understand why our bodies make it or how what we eat affects the levels of insulin we produce. More so than any other hormone, our diet is key in regulating insulin levels, and thus a number of biological processes. As you’ll soon see, everyone should think about how what they eat impacts their body’s insulin release to be at their happiest and healthiest.

Why We Need Insulin

Every living thing requires energy to survive. In cells, energy is stored and shuttled around using a molecule called Adenosine Tri-Phosphate, or ATP. Whenever the cell then has an energy-requiring reaction, enzymes can use the energy stored in ATP’s phosphate bonds to fuel it. Cells rely on ATP to survive, and to create ATP, they rely on glucose.

ATP – the fuel for life

All cells, from bacteria and fungi to us, take glucose and use it to generate ATP by a process called Oxidative Phosphorylation. First, glucose is converted to an intermediate molecule called pyruvate via a process called glycolosis. As long as there is oxygen around, this pyruvate is further converted to Acetyl CoA, which enters a cycle of reactions called the Citric Acid Cycle. This takes the carbon to carbon bonds and uses them to create high energy electrons, which are then passed down a chain of enzymes which use the electron’s energy to create a proton gradient, the force of which fuels ATP synthase, the enzyme which creates ATP from ADP. Without glucose, cells cannot create ATP, and eventually die.

In plants, a process called photosynthesis takes light energy from the sun and uses it to combine carbon dioxide (CO₂) and water (H₂O) to create glucose (C₆H₁₂O₆). This means that to survive, all they need is light, air and water. Unlike plants, though, we cannot create our own glucose, so we rely on our diets to provide it for us.

Just about everything we eat is able to be used to create glucose. Carbohydrates, by definition, are sugars, and all sugars are readily converted to glucose. The amino acids that make up proteins can be converted to glucose via an enzymatic process called gluconeogenesis. Fats, too, are converted to glucose or its derivatives; glycerol, for example, can be converted to glucose via gluconeogenesis, and fatty acids can be converted to Acetyl CoA via beta oxidation. No matter where it comes from, the glucose from our meals then ends up in our blood to travel around our bodies to the tissues that need it.

Obviously, having a blood glucose level that is too low would be bad – not enough glucose will get to our various tissues, and our cells won’t be able to generate enough ATP to function. This is a condition known as hypoglycemia, and the effects can range from mildly ‘feeling bad’ to seizures, unconsciousness, permanent brain damage or even death, all of which are due to a lack of ATP. But you can tip the scale too far in the other direction, too. You would think that since it’s so important, we would want a ton of glucose in our blood, but too much causes our blood to thicken, slowing it down and drawing fluid from our tissues to try and make it thin again. Too high of a blood glucose level, called hyperglycemia, can result in blurred vision, fatigue, dry mouth and heart problems that can sometimes be fatal. So our bodies work very hard to maintain our blood glucose levels between 3.6 and 5.8 mM (mmols/liter). This is about enough glucose to provide energy to the body for 20-30 minutes, so as we use up the glucose in our blood, our bodies constantly release more (hopefully) without overdoing it.

It’s particularly important for our bodies to maintain glucose levels every time we eat. Whenever we ingest food, our bodies have to quickly adjust to the sudden flood of glucose entering our systems as our meals are digested. Take something as small as a roll of Smarties, for example. One roll of Smarties contains 6 grams of sugar. At around 125 lbs, my body contains an average of 4 liters of blood. This means that if all the sugar from a single roll of those delicious candies were to enter my bloodstream at once and remain unchecked, it would raise by blood sugar by 8 mM! Four smarties packs, and my blood sugar levels would be fatal. So why, then, when I enjoy a sugary treat, do I not go into severe hyperglycemia?

The answer is insulin. Our bodies release insulin right before and during eating, and that insulin tells our bodies to start taking glucose out of the blood, thus lowering our blood glucose levels. It does this by both promoting uptake of glucose by cells and the storage of glucose within our cells. Without insulin, we would all go into hyperglycemic shock and die from something as common as a hamburger.

What is Insulin?

Insulin is a relatively small peptide hormone produced by β-cells in the pancreas. It’s main job is to signal the liver, muscle and fat tissues to take up glucose from the blood and store it as glycogen. As the glucose level in the blood drops to normal, insulin release slows or stops. If it drops too low, an antagonistic hormone, called glucagon, is released which does the opposite of insulin, stimulating cells to break down glycogen and release glucose.

The insulin and glucose process illustrated

But insulin does much more than just control blood glucose levels. Its effects depend on the cell type that receives its signal. Fat cells, for example, don’t take up or store glucose. Instead, they respond to insulin by taking the fats that enter the blood stream and turning them into fatty acids, which they store in large vacuoles. Thus insulin promotes the uptake and storage of fat in our adipose tissues. While insulin levels are high, our bodies don’t digest or use fats for fuel. Instead, we rely on the glucose in our blood and tissues. This is key to keep in mind when trying to lose weight – you body simply won’t break down and use your fat reserves with insulin around.

Furthermore, insulin stimulates the body to absorb most amino acids. However, it doesn’t lead to intake of tryptophan by cells. This creates an effective rise in tryptophan concentration in the blood, allowing it to pass through the blood brain barrier. In the brain, tryptophan is converted to serotonin, a neurotransmitter whose primary purpose, in this case, is to reduce appetite. But serotonin has a lot of other effects, as those of you who have read the previous Understanding Our Bodies on Serotonin know well. In general, increased serotonin leads to a feeling of happiness and calm, which is why we get such satisfaction when we eat. Thus insulin is important not just when it comes to dealing with fats and sugars but in regulating our emotions, too!

It turns out insulin in the brain has a lot of functions, very few of which we understand well. Mice that lack insulin and leptin receptors in their brains, however, exhibit insulin resistance that is characteristic of diabetes. Strangely, though, they have a lot of reproductive deficiencies, too – the females have poor fertility, high testosterone levels and deformed ovaries, for example. Why insulin has these effects on reproduction is unknown, but it just goes to show that insulin does a lot more than regulate blood sugar levels, and is far more important in our bodies than we once thought.

Regulating Insulin

While insulin levels are mostly regulated by the amount of glucose in our blood, other things can stimulate its release. Other molecules from digestion, like certain amino acids, proteins and lipids, can similarly stimulate insulin release. But most incredibly, our bodies begin releasing insulin before we even take a single bite of food. When we think about, smell, or slightly taste foods, our brains trigger what is called Cephalic Phase Insulin Release. A food’s color, appearance, flavor, aroma, and texture can all impact how our brains respond to the idea of eating it. The goal is to prepare the body for what the brain thinks will be a sudden flood of glucose. The sweeter and sugarier the brain thinks the meal will be, the more insulin it stimulates the pancreas to release before the food even enters the mouth.

Merely waiting in line for food can ramp up the body’s insulin system – credit, flickr -Eleets121

Once we start to eat, our bodies ramp up insulin secretion, in what is often called first phase insulin release. Insulin that was kept in storage while our blood glucose levels were normal is released all at once, leading to a dramatic increase in insulin levels. The amount of insulin secreted in the first phase response to a meal is determined by the amount of glucose encountered in the previous meal – the more you needed last time, the more is released in this first phase. In a healthy person, this first phase response peaks a few minutes after you’ve started your a meal.

The β-cells then take a quick pause. If the first pulse was enough, then they slowly take up the insulin they released, and store it for the next meal. If the blood glucose levels stay high, though, the β-cells begin producing and releasing insulin in pulses every ten to twenty minutes. They continue this until the body’s blood glucose gets back to normal levels. The blood sugar rise caused by the meal peaks about half an hour after eating, and this, in turn, leads to a decrease in insulin production and release.

There are other regulators of release of insulin, too. Stress hormones like noradrenaline inhibit insulin release. This makes sense when you think about it evolutionarily. The purpose of stress hormones is to prepare our bodies for a sudden need to act. If we see a tiger, for example, our stress hormones spike so we can be prepared to fight if it attacks or run like hell to get away. Either way, we’ll need extra energy on hand to deal with the stressful situation, so stress hormones stop insulin from being released to ensure that a little extra glucose is in the bloodstream and able to reach whatever body parts need it most.

Not all insulin is produced in the pancreas, though. The brain also produces its own supply of insulin. The brain is a complex organ and needs lots of fuel to run properly. Insulin in the brain enhances learning and memory. Meanwhile, reduced levels of insulin and its related proteins are linked to Alzheimer’s disease and other degenerative disorders.

Insulin and Disease

Insulin is at the heart of many diseases. As I just explained, insulin in the brain is particularly key, and can lead to neurological disorders. But too much or too little insulin in the body is a big problem, too. There is a special name for the series of diseases caused by impaired insulin signaling in the body. You might have heard of it: Diabetes Mellitus.

When your body stops producing insulin, injections are all that is left – credit, i5a, flickr

Diabetes occurs when the body does not have the insulin signaling it should. There are two major types: type 1 and type 2. People with type 1 diabetes tend to realize their condition early in life, and must deal with it throughout their lifetime, while those with type 2 tend to develop symptoms later on. What’s the difference? While both conditions involve problems with the insulin pathway, type 1 diabetes is caused by a lack of insulin, while type 2 is caused by chronically high levels. People with type 1 diabetes have innately low levels of insulin due to genetic mutations. Without the ability to produce enough of this vital hormone, they usually have consistently high blood glucose levels. While this is a problem, there are many forms of treatment, including insulin injections. By carefully controlling their sugar intake and taking insulin when they need it, people with type 1 diabetes can regulate their blood glucose levels to being almost normal.

Type 2 diabetes is different. Type 2 diabetes results from the body having high insulin levels for too long. Insulin is meant to be a fast acting hormone – you release it when glucose levels are high, so that they drop. Then the signal stops. If you constantly eat too much or have a very sugary diet, you can end up with high insulin levels all the time. This leads to the body becoming desensitized to insulin. It’s kind of like trying to listen to a radio with static. If you only get a little static every once in a while, you can hear the song fine, and understand what the artist is saying. But start having high static all the time and you can’t tell what song is playing anymore. Your body, in effect, can’t tell what signal it’s supposed to be getting, and instead stops listening all together. Type 2 diabetes is that much more dangerous because the body will rarely respond to insulin treatment, meaning that drastic diet changes and exercise are the only ways to fight back.

Sadly, more than 90% of diabetes cases are type 2. Prevalence rates of type 2 diabetes doubled between 1990 and 2005, causing the CDC to declare it an epidemic.

Insulin is also a key player in Metabolic Syndrome. Metabolic syndrome, often called prediabetes, is poorly characterized, and even more poorly understood. Symptoms include elevated blood pressure, high blood cholesterol, and increased waist circumference. The main cause appears to be decreased response to insulin in certain tissues, specifically muscle and fat. The thing is, we’re not sure if it’s treatable or an irreversible first step in Type 2 diabetes. Often, people with metabolic syndrome are overweight, and at higher risk for other, even more life threatening conditions like heart disease. While some drugs can be prescribed to treat the symptoms like high blood pressure, the only long-term solution is to lower chronic blood glucose levels and restore insulin sensitivity, if, indeed, it can be restored at that point.

Nutrition and Insulin: Glycemic Indexes, Glycemic Loads and Beyond

Everyone should think about insulin and blood glucose levels, not just people with diabetes or metabolic syndrome. What we eat, how much of it, and when can impact our insulin release, which in turn can have a big impact on our bodies and how we feel.

Refined carbohydrates like spaghetti can exacerbate blood sugar issues – credit, flickr, Bxl06

The major dietary players in insulin regulation are carbohydrates. While fats, proteins and everything else can increase blood glucose levels, carbohydrates do it much faster for two simple reasons: firstly, they’re one of the first things we break down in digestion. There are enzymes in our saliva that begin carbohydrate breakdown before the foods even reach our stomachs! But more importantly, carbohydrates lead to immediate rises in blood glucose because they contain glucose. Other molecules must first be converted to glucose, but carbohydrates, which include sugars, just need to be hacked into pieces by our digestive enzymes. Different carbohydrates contain different amounts of the monosaccharides, like glucose or fructose. Thus they each have different impacts on immediate rises in blood glucose levels.

This difference in effect on blood sugar level is the basis of the Glycemic Index, or GI. The glycemic index rates foods based on how much of an immediate impact they have on blood glucose per 50 grams of carbohydrate. If you picture the rise in blood glucose levels in response to a food on a graph over time, the glycemic index is a number that is related directly the area under a two-hour curve. The higher the spike in blood glucose levels, the larger the area under the curve is, and thus the higher the glycemic index, which is somewhere on a scale of 1 (low) to 100 (high). Most foods that have a low GI induce lower spikes in insulin, but not all of them. There is another index, called the Insulin Index, that looks directly at rises in insulin levels. While the glucose and insulin scores of most foods are related, high-protein foods and baked goods that are rich in fat and refined carbohydrates usually elicit much higher insulin responses than their glycemic index values would suggest.

Research into the glycemic index have found strong support of the idea that low GI foods are better for us. People who eat less high GI foods have lower risks of developing both type 2 diabetes and heart disease. It’s uncertain if this is due to overall lower blood sugar levels or reduced glycemic “spikes.” When glucose levels increase dramatically, our bodies ramp up the release of insulin and the processing of glucose from the blood, including ATP generation. While ATP is great, the process by which we make it – oxidative phosphorylation – has side effects. Mainly, the faster it’s churning, the more likely the machinery is to leak reactive oxygen species (ROS). These oxygen radicals are highly reactive and tend to transform whatever they come in contact with, which can cause damage to proteins, membranes, or even our DNA. By eating foods that increase glucose levels more slowly, we limit ROS bursts that can damage our cells.

The glycemic impact of foods can be strikingly different for your body

However, the glycemic index isn’t perfect. Glycemic indices aren’t the whole story since they are based on a per-carbohydrate basis. Two foods that have the same GI can have dramatically different effects on blood glucose per serving if one has significantly higher carbohydrate content than the other. The affect a serving of food has on blood glucose is referred instead to its Glycemic Load. Glycemic load is calculated by multiplying the weight (in grams) of carboydrate in a serving by the food’s overall GI and divided by 100. A GL of 10 or less is considered low, while 20 or more is considered high. Let’s say you want to eat a baguette, for example. Both whole gain and French baguettes have similar GIs (roughly 73). But there’s a lot less carbohydrates per serving in the whole gain loaf, and thus its GL is only 9 while the GL of the french baguette is 27!

The GI or GL of a food isn’t the only thing you should consider when it comes to insulin and your diet. When you eat matters a lot, too. Our bodies react to the same foods differently at different times of day. Morning is a special time for your body because you’ve just spent a while in a comatose state. The changes your body undergoes while you sleep can have a dramatic impact on how it responds to food. Insulin levels tend to be low in the early morning, for example, because your body releases stress hormones just before you wake up. Once you’re awake, though, your body ramps up insulin secretion to metabolize the high glucose levels and give your cells a little fuel to start the day with.

These alterations have a big impact on how our diets affect us. When different foods were tested for their GI values at different times of the day, for example, researchers found that the same food eaten for lunch instead of breakfast induced a lower glucose response. This is why it may be particularly important to eat a protein-rich breakfast, like eggs, instead of high glycemic foods like white bread toast. Time of day has been found to have a larger effect on insulin responses in women than in men, though no one understands why. Furthermore, studies have shown that the quality of sleep you get affects how strongly your body reacts to food. A restless night can lead to higher glucose responses and larger spikes in insulin in response to food in the morning. So getting a good night’s sleep is also important in preventing the kinds of spikes which may be a major factor in type 2 diabetes.

Also, foods can interact with each other to lower or raise the GI values of a meal. For example, foods that contain fiber, protein, or fat will generally reduce the GI of the meal as a whole. Recent studies have even shown that having a small volume of alcohol (one drink) prior to a meal reduces the GI of the meal by 16-37% – which, as far as I’m concerned, is fantastic news. Furthermore, many cultures eat high GI foods like potatoes or rices but have low occurrences of diabetes and obesity. The truth is we have yet to tease out all the factors that lead to these conditions, and the GI level of our diets is likely only one of many related factors.

The Even Bigger Picture

Clearly, what we eat, with what and when matters a lot when it comes to insulin levels. This is important in keeping healthy and reducing the risk of metabolic syndrome and type 2 diabetes. But insulin affects so many other things in our bodies, from amino acid uptake to fat storage. We need to consider insulin whether we’re worried about type 2 diabetes or not!

Thinking about how our diet affects insulin is especially key when trying to lose weight or maintain a healthy weight. Insulin actually triggers the storage of fats in adipose tissues, so sustained high levels of insulin promote weight gain! Furthermore, recall that our bodies don’t break down fat while insulin is circulating. This means that if we eat foods with high GIs that produce sustained insulin levels, we’re shooting ourselves in the foot, even if we eat less calories overall.

Understanding how our bodies regulate insulin release also explains why certain foods are worse for us than we’d expect. Sugary drinks are particularly bad for us, for example, even when we take into account their calorie and sugar content. This is because our brains don’t judge their sugar content well in advance. Thousands of years of evolution led our brains to believe that drinks, overall, were low-cal things that mostly contain water. Our brains aren’t wired to think that fluids contain a lot of sugar. Thus when we look at a soda or even begin to sip one, we don’t have the same level of cephalic phase insulin release or first phase insulin release that we would for a solid treat. The end result of this is that our bodies are unprepared for the sudden sugar rush, and have to instead release a massive amount of insulin all at once to deal with what it considers an inexplicable rise in blood glucose.

High spikes in insulin lead to dramatic drops in blood glucose, which can cause your body to feel hungry sooner. Eating low GI and GL foods can help you lose weight by making you feeling fuller longer. Low GI foods don’t cause dramatic drops in glucose levels, thus you tend eat less throughout the day. It’s thought that this effect, on top of the high-sensitivity of our bodies to high GI foods in the AM, is why eating eggs, a low GI food, instead of cereal or toast in the morning has been found to reduce overall food intake for the day by as much as 18%. You can create lower spikes in insulin not only by avoiding sugary drinks and eating lower GL foods but also by eating smaller meals. This is because the amount of first phase insulin release is dependent on the amount of insulin needed for the previous meal. The bigger meals are, the larger the spike at the beginning of every meal, and the bigger the drop in glucose afterward.

But you shouldn’t just cut out everything that leads to insulin release! Insulin is important, and too little is just as bad as too much. Even small drops in daily insulin levels can affect us negatively. For example, dieters often experience depression around 2 weeks after they begin cutting high-glycemic foods like carbohydrates out of their diet. Why? Because they have much lower levels of insulin than they did before. Decreased insulin means decreased amino acid uptake, and because the level of other amino acids affects how well tryptophan crosses the blood brain barrier, decreased insulin means less serotonin which leads to, in layman’s terms, feeling like crap. While you should monitor the GI of your meals to reduce insulin spikes, you shouldn’t go for rock bottom either. At least you shouldn’t if you want to be happy about it!

Previous posts in the Understanding Our Bodies series:

Citations:

Van Cauter E, Polonsky KS, & Scheen AJ (1997). Roles of circadian rhythmicity and sleep in human glucose regulation. Endocrine reviews, 18 (5), 716-38 PMID: 9331550

Hill, J., Elias, C., Fukuda, M., Williams, K., Berglund, E., Holland, W., Cho, Y., Chuang, J., Xu, Y., & Choi, M. (2010). Direct Insulin and Leptin Action on Pro-opiomelanocortin Neurons Is Required for Normal Glucose Homeostasis and Fertility Cell Metabolism, 11 (4), 286-297 DOI: 10.1016/j.cmet.2010.03.002

Spiegel K, Knutson K, Leproult R, Tasali E, & Van Cauter E (2005). Sleep loss: a novel risk factor for insulin resistance and Type 2 diabetes. Journal of applied physiology (Bethesda, Md. : 1985), 99 (5), 2008-19 PMID: 16227462

Brand-Miller JC, Fatema K, Middlemiss C, Bare M, Liu V, Atkinson F, & Petocz P (2007). Effect of alcoholic beverages on postprandial glycemia and insulinemia in lean, young, healthy adults. The American journal of clinical nutrition, 85 (6), 1545-51 PMID: 17556691

Ratliff J, Leite JO, de Ogburn R, Puglisi MJ, VanHeest J, & Fernandez ML (2010). Consuming eggs for breakfast influences plasma glucose and ghrelin, while reducing energy intake during the next 24 hours in adult men. Nutrition research (New York, N.Y.), 30 (2), 96-103 PMID: 20226994

Understanding Our Bodies: The Role of Antioxidants

nutrition — Mon, 26 Oct 2009 10:04:36 +0000

It seems like every day there’s a new super-food that is chock full of antioxidants and ready to cure everything from the flu to cancer. Antioxidants are touted as a nutritional panacea, but I would bet that few people really understand what antioxidants are, how they function in the body, and how including them in their diet makes an impact.

These are the antioxidants you want – from flickr user crabchick

Are antioxidants good for you? The short answer is yes, but buyer beware. Just because something is good for you doesn’t mean you should start taking a giant mega-dose of it. Antioxidants are great when the come from natural sources as a part of a healthy diet. But like everything else, a closer look at their physiological action explains why you can get too much of a good thing.

It’s All About The ROS

What are antioxidants? To answer that question, you have to understand reactive oxygen species, or ROS. And to do that, you have to understand how your cells produce energy. So here we go: a very quick overview of cellular energy metabolism.

In human cells, like other eukaryotes (everybody but the bacteria), energy is made in a specialized cellular structures called mitochondria. Mitochondria are these strange, double-membraned organelles that are highly specialized – they contain their own DNA, make their own proteins, and are tightly regulated by the cell. Essentially, mitochondria are energy powerhouses, or the cell’s equivalent of a power plant. Below is a 3D view of the structure (thanks to T. G. Frey of San Diego State University):

watch : http://www.sci.sdsu.edu/TFrey/?MitoMovies/CrisMitoER.mov

Using a complex process, mitochondria take our fats, carbohydrates, and excess proteins and turn them into a four-carbon molecule called Acetyl CoA. This molecule goes through a series of reactions in what is called the Kreb’s Cycle which results in the creation of high-energy electrons taken from the bonds.

These electrons are then passed down a chain of enzymes which use the energy they possess to create a proton (H⁺) gradient between the center of the mitochondria and the between-membrane space, eventually reducing oxygen into water (O₂ –> H₂O).

It’s this proton gradient that is used to drive an enzyme called ATP synthase, which creates ATP, the functional energy molecule used by our cells.

But the system isn’t perfect. Every once in awhile, instead of making harmless water, the chain makes unstable oxygen molecules, which are referred to as free radicals. These molecules are dangerous to the cell because they are highly reactive – in other words, they attack chemical bonds – hence their other name, reactive oxygen species (ROS). They can cause damage to DNA, enzymes, proteins and many of the other vital components of a healthy cell.

Luckily, our bodies have innate mechanisms to deal with ROS, like the enzyme catalase which converts hydrogen peroxide (a kind of ROS) into water and oxygen. But as we age, our mitochondria get less and less efficient, producing more and more ROS. If too many ROS are produced and they overwhelm our innate damage repair mechanisms, our cells suffer, and either become non-functional or even cancerous.

That’s where antioxidants come in. Antioxidants are compounds which react with free radicals and neutralize them, thus protecting our bodies from oxidative damage by ROS. They vary widely and are found in all kinds of foods we eat every day. Perhaps the most famous antioxidant foods are the colored berries like blueberries and raspberries, which are chock full of a antioxidants like Vitamin C and Vitamin E.

So ROS are bad?

Well… like everything else, it’s not quite that simple. Yes, reactive oxygen species can be very damaging. Some scientists finger them as the direct cause of aging, and because of the damage they can cause, they are thought to play a pivotal role in many diseases from Alzheimer’s to cancer. ROS production is increased in people who are overweight or obese, and is considered one of the reasons why weight gain is so damaging to the body.

But many ignore the fact that ROS are a normal and regular part of cell metabolism. Even when we’re healthy, we boost the production of ROS when we exercise and when we eat. As it turns out, we need them. They are important in a number of cellular pathways, including those related to programmed cell death (apoptosis), as they are a direct measure of how much energy is being created by a cell at a given time. Increases in ROS may actually be beneficial at the right times.

For example, one study found that if you up the ROS in mice being fed a high fat diet, you actually prevent them from becoming insulin resistant. Insulin resistance is the first step towards diabetes – it occurs when our bodies stop responding effectively to the insulin we release to store glucose uptake.

Over time, eating too much (especially too much sugar) leads to a constantly high insulin levels, and our bodies simply become less sensitive to insulin. ROS, as the researchers explain, are key in insulin signaling, and without them, our cells can’t respond efficiently to insulin.

“In the case of early type 2 diabetes and the development of insulin resistance, our studies suggest that antioxidants would be bad for you,” explains Tony Tiganis of Monash University in Australia.

Furthermore, increases in ROS are pivotal in the heart’s ability to prevent damage during a heart attack. If you boost ROS signals before a heart attack, it allows the cells to precondition and prevents later damage from oxygen deprivation. This pathway, including ROS, are being evaluated as targets for therapeutics and pharmaceuticals to reduce or prevent heart damage.

As with anything, ROS are healthy for you when they’re kept balanced by the body’s defensive enzymes and antioxidants. Natural, low-ish levels of ROS signaling, like that produced when you eat a good diet and exercise, is good for you. But get too much of a good thing – like when your body’s natural oxidation defenses break down – and it becomes a bad thing. Eating a variety of fruits and vegetables, packed with antioxidants, has been shown to improve the body’s ability to deal with ROS properly, improving all kinds of physiological parameters and aiding in the prevention or treatment of a wide variety of diseases.

Should I take extra antioxidants?

Increases in overall fruit and vegetable intake have shown to be great for our bodies, but this is likely due to the interplay between many different compounds. The jury is still out on whether supplementing your diet with specific antioxidants improves your health.

Clinical trials have had remarkable trouble finding actual benefits from supplementing diets with individual or even combined antioxidants. A vegetable or fruit is better for you because doesn’t just contain one or two antioxidants; it also contains a balance of vitamins, minerals and enzymes that are impossible to reproduce in pill form.

And more importantly, you can over do it. The line between healthy and unhealthy blurs when it comes to dietary supplementation with excessive amounts of antioxidants. For example, you smokers out there might want to watch your beta-carotene intake. Beta-carotene is an antioxidant, found in many vegetables including kale and spinach, and researchers had hoped that supplementing the diets of smokers with it and another antioxidant, retinol, would help prevent lung cancer.

But the reverse occurred – beta-carotene was found to actually increase the risk of lung cancer and death when taken as a supplement by those who were at high risk for the disease. Why it had this strong, negative effect is not fully understood, but it serves as a warning that over-supplementing isn’t a good idea.

Similarly, a meta-analysis of clinical trials involving Vitamin E found that high doses – >400 IU a day – increased risk of mortality. It’s likely that in both these cases, the excessive levels of antioxidants actually prevented the ROS from doing their job as signaling molecules, screwing up cellular signaling pathways including those that lead to cell death. Cells that don’t die when they should are at high risk for becoming cancerous.

You probably aren’t going to do yourself any damage by eating all the antioxidants you want – and, more likely, you’ll improve your diet. But don’t try and overdo it with pills. Cramming ten extra Vitamin C tablets isn’t going to do you any good. Antioxidants are better when they come straight from the source, as they exist in a form your body is prepared to use.

Studies have shown supplements simply don’t cut it, and super pills don’t replace eating a healthy, balanced diet with at least five servings of fruits and veggies a day. And in some cases, antioxidant supplements increase the risk of cancers, like beta-carotene did for smokers, and can be particularly damaging for those already on certain drugs.

If you really insist on taking supplement pills, be sure to talk to your doctor first and make sure what you’re taking is actually good for you and isn’t going to conflict with other medications. So-called nutritional supplements often tout amazing health benefits without any actual science to back them up.

Previous posts in the Understanding Our Bodies series:

References:

Stadtman, E. (1992). Protein oxidation and aging Science, 257 (5074), 1220-1224 DOI: 10.1126/science.1355616
Liu, J. (2002). Memory loss in old rats is associated with brain mitochondrial decay and RNA/DNA oxidation: Partial reversal by feeding acetyl-L-carnitine and/or R-alpha -lipoic acid Proceedings of the National Academy of Sciences, 99 (4), 2356-2361 DOI: 10.1073/pnas.261709299
Zhang JW, Rubio V, Zheng S, & Shi ZZ (2009). Knockdown of OLA1, a regulator of oxidative stress response, inhibits motility and invasion of breast cancer cells. Journal of Zhejiang University. Science. B, 10 (11), 796-804 PMID: 19882753
Rhee SG (2006). Cell signaling. H2O2, a necessary evil for cell signaling. Science (New York, N.Y.), 312 (5782), 1882-3 PMID: 16809515
Loh, K., Deng, H., Fukushima, A., Cai, X., Boivin, B., Galic, S., Bruce, C., Shields, B., Skiba, B., & Ooms, L. (2009). Reactive Oxygen Species Enhance Insulin Sensitivity Cell Metabolism, 10 (4), 260-272 DOI: 10.1016/j.cmet.2009.08.009
Vanden Hoek T, Becker LB, Shao ZH, Li CQ, & Schumacker PT (2000). Preconditioning in cardiomyocytes protects by attenuating oxidant stress at reperfusion. Circulation research, 86 (5), 541-8 PMID: 10720416
Valko M, Leibfritz D, Moncol J, Cronin MT, Mazur M, & Telser J (2007). Free radicals and antioxidants in normal physiological functions and human disease. The international journal of biochemistry & cell biology, 39 (1), 44-84 PMID: 16978905
Wallig MA, Heinz-Taheny KM, Epps DL, & Gossman T (2005). Synergy among phytochemicals within crucifers: does it translate into chemoprotection? The Journal of nutrition, 135 (12 Suppl) PMID: 16317157
Goodman GE, Thornquist MD, Balmes J, Cullen MR, Meyskens FL Jr, Omenn GS, Valanis B, & Williams JH Jr (2004). The Beta-Carotene and Retinol Efficacy Trial: incidence of lung cancer and cardiovascular disease mortality during 6-year follow-up after stopping beta-carotene and retinol supplements. Journal of the National Cancer Institute, 96 (23), 1743-50 PMID: 15572756
Miller ER 3rd, Pastor-Barriuso R, Dalal D, Riemersma RA, Appel LJ, & Guallar E (2005). Meta-analysis: high-dosage vitamin E supplementation may increase all-cause mortality. Annals of internal medicine, 142 (1), 37-46 PMID: 15537682
Rodrigues MJ, Bouyon A, & Alexandre J (2009). [Role of antioxidant complements and supplements in oncology in addition to an equilibrate regimen: a systematic review] Bulletin du cancer, 96 (6), 677-84 PMID: 19493854

New Study Connects Leptin to Dopamine

nutrition — Mon, 10 Aug 2009 08:43:47 +0000

As I’ve been writing the “Understanding Our Bodies: The Physiology of Nutrition” series, I’ve tried to explain how the various chemical systems in our bodies relate to how and what we eat. For example, two of the biggest hormones that affect our eating habits – Leptin, the fullness hormone, and Dopamine, the brain’s reward hormone – seem to have very different and unrelated effects on our bodies. But every day science is discovering just how interwoven and related our bodies different systems are.

Just this week, for example, after explaining everything I could find about how dopamine relates to eating, scientists from the University of Michigan have discovered a new way that leptin regulates dopamine levels. The study, published in the journal Cell Metabolism, reveals for the first time that the brain’s lateral hypothalamic area (LHA) has neurons which receive signals from leptin and in turn directly feed into the central dopamine system in another area of the brain, the ventral tegmental area (VTA). Because of this, the amount of fat in our bodies (and everything I talked about in the Leptin article) has a direct influence on the amount of dopamine circulating in our brains.

What did the researchers do?

Leptin is high when you are full, low when you are hungry

Most studies that look at leptin focus on one area of the brain: the arcuate nucleus. This is the area that is largely affected by leptin levels and the subsequent effect on appetite. Remember, when leptin levels are relatively high, we aren’t hungry, and when they drop, we want to eat. But this area of the brain isn’t the only one with leptin-responsive neurons, called “LepRb” neurons.

The researchers found that the lateral hypothalamic area (LHA) also contains these LepRb neurons. Other studies have found that a related area, the ventral tegmental area (VTA) also contained a few of these LepRb neurons, and that leptin stimulation there had an effect on dopamine. Other researchers have found that, in general, the LHA has a strong affect on the VTA. But no one had ever looked at how the LHA related to leptin or the VTA’s dopamine. So, the scientists decided to probe a little deeper.

They took rats and injected leptin directly into the LHA portion of their brains. What they found was that these rats ate less and lost weight. In turn, by sampling brain tissue from the rats, they found that leptin in the LHA caused a 40% increase in dopamine in the VTA as well as a 2.5-fold increase in gene transcription related to dopamine. Simply put, leptin in this area of the brain caused a strong increase in dopamine that was previously unknown to science.

What does this mean?

The fact that leptin has a direct affect on dopamine levels means that its controlling more that just our appetites in terms of the food we feel a need to eat, it’s controlling what we want to eat. It’s affecting both our needs and our desires. This increase in brain dopamine likely influences our abilities to avoid tempting foods like sugars and carbs when our bodies don’t actually need them. So if you’re leptin-deficient because of crash dieting or leptin-insensitive because of obesity, you likely feel stronger and harder to resist urges for these foods, making staying healthy or losing weight even more difficult.

The body’s systems are linked in ways we are only beginning to understand

It makes sense that leptin would have an effect on the brain’s reward systems. After all, we know that a decrease in dopamine can lead to cravings for food even though our bodies doesn’t need it. If a hormone is to properly control appetite, it would have to have some affect on the dopamine system to prevent unnecessary overeating. Way back when, when humans were evolving, overeating could be costly. When food is scarce, using up what little food is available could mean starvation. So there would be a strong selective pressure to prevent the body from eating too much when it doesn’t need it nutritionally.

The good news is, these results suggest that our bodies do some of the hard work for us. If we can get our bodies to a healthy weight with good nutrition, the natural leptin levels will help control our desires for bad foods, making it easier to stick to the good we’ve done. On the downside, it means that upsets to our leptin system like crash dieting or obesity have an even more marked impact because they throw off our dopamine levels, too. The scientists in this study note that exactly what happens to dopamine when the leptin system is off is a key area of study for the future.

As always, this study is yet another reminder that there is a cost to eating poorly and a much bigger benefit to eating healthy and being fit. It’s not just about weight. Dopamine controls our overall needs and desires, feelings of self gratification, and overall happiness. Eating right is about not only how good we look but how good we feel. You’d be surprised at how strong an effect nutrition has on our emotions.

Reference: Leinninger, G., Jo, Y., Leshan, R., Louis, G., Yang, H., Barrera, J., Wilson, H., Opland, D., Faouzi, M., & Gong, Y. (2009). Leptin Acts via Leptin Receptor-Expressing Lateral Hypothalamic Neurons to Modulate the Mesolimbic Dopamine System and Suppress Feeding Cell Metabolism, 10 (2), 89-98 DOI: 10.1016/j.cmet.2009.06.011

Understanding our Bodies: Dopamine and Its Rewards

nutrition — Fri, 31 Jul 2009 08:47:11 +0000

As much as we’d like to deny it, there’s a lot more involved in our decision making when it comes to food than just the advice of our inner and outer nutritionists. For the most part, we know that we should be eating. Yet time and time again when a friend asks us if we want to go grab a Big Mac or when we’re walking down the aisles in the grocery store, we neglect our own advice. Why? Why are those foods that are so terrible for us so darned appealing?

Would you believe me if I said it all has to do with 4-(2-aminoethyl)benzene-1,2-diol? Well, you might, if I explained that “4-(2-aminoethyl)benzene-1,2-diol” is the chemical name for the infamous addiction neurotransmitter Dopamine.

The Deal with Dopamine

The reason bad foods taste so good, dopamine.

Dopamine is one of our body’s neurotransmitters. It’s one of the most common biochemical compounds in animals, and is found in everything from invertebrates to us. It has a variety of functions, not all of which are fully understood. We do know that it is key in behavior, cognition, motivation and reward. In other words, it helps tell your body when you’ve done something good, and promotes our brains to remember what we did that was good and repeat to get the reward again.

When we receive a reward of any kind, dopamine is released in our brains. Over time, this stimulus and release of dopamine can lead to learning. Researchers have recently found that how quickly and permanently we learn things relates directly to how much dopamine we have available in our brains. As we get rewarded over and over again for something, we learn that we should keep doing whatever that is very deeply, and it’s hard to unlearn those kinds of behaviors.

Logically, it’s one of the neurotransmitters targeted for treatment of addictions. Whether chemical or psychological, addictions are made when our brain gets a dopamine boost over and over from a behavior. We learn to not only associate that behavior with the happy reward, but to crave to do that behavior when the rewards aren’t around. Even when there are better, easier, and less destructive ways to make ourselves feel better, our brains are trained to do that one action that it is used to doing – a drug, a drink, sex, whatever – to feel that satisfaction again.

One of the reasons cocaine is so addictive, for example, is that it prevents the brain from removing dopamine from the space between neurons as quickly, causing reward circuits to fire for longer and more intensely than they normally would. Thus anything done on cocaine that causes a dopamine release feels even better – like if someone hands you a dollar, you feel like you’ve been given a twenty instead. When users stop, suddenly life itself just seems less rewarding, and their bodies crave that happier, more-fulfilled state of mind.

Effects of cocaine on dopamine activity in the brain

The important thing to note is that dopmaine doesn’t change the pleasure (or lack thereof) involved with a behavior, just how much we want to do it. For example, rats who have been artificially depleted of dopamine simply won’t eat, but when force fed, they make facial expressions which suggest they actually enjoy it. Similarly, increasing dopamine makes rats crave sweet rewards more, but doesnt change how much they actually like them. Even if you don’t like something at all you can end up wanting to do it if it causes some kind of consistent dopamine release.

Dopamine and Eating Behaviors

This is important to our diets because, for one, we get little dopamine rewards when we eat. The more spaced out your meals are, the more time your body spends with lowered dopamine levels. Thus eating smaller meals more frequently actually keeps dopamine levels higher. People who have genetically low levels of dopamine have been shown to be more likely to overeat, most likely because they aren’t getting enough of a dopmaine response. Similarly, the more dopamine receptors a person has, the better control they have of their diet and what they eat. Unfortunately, genetics can have a lot to do with it, so for some people, sweet rewards are harder to fight.

But it gets worse. The exact conditions when we receive our “reward” stimulus are imprinted on our brains, too. Research has shown that rats that are given chocolate in a given situation learn to expect it, and the same situation triggers reward networks in the brain even without the chocolate being present. So once our brains connect bad food with a particular mood, feeling or state of mind, it’s hard to reverse it. For example, if eating dinner is a time when family gets together, people feel warm and friendly, and are bonding, then when later in life you’re feeling lonely, you might try eating to make yourself feel better. This is especially true for people who are conditioned at a young age to associate sweets with some kind of good deed – get an A, get to eat a sweet otherwise forbidden. Later, when they want the same feeling of accomplishment, they often turn to the food stimulus to create the feeling. It’s exactly why we all know what “comfort food” is.

The temptations of your sweet tooth. (thanks jujuly25)

And, of course, then there’s the worst part: unhealthy foods actually trigger the brain’s reward systems better than healthy ones. Sugar and sweets can trigger the brains reward systems completely separate of their tastes. In our bodies, it appears, dopamine release is calorie-dependent, thus the more you eat in a sitting, the more dopamine is released, and the more rewarding the meal is. Of course, very dense calorie-packed junk foods just lying around waiting to trigger your brain’s reward system make it that much harder to eat healthy. And, of course, over time if you eat a lot of sugary, high-calorie foods, your brain’s dopamine system gets desensitized, making it harder and harder to get the same reward from those foods, meaning you eat more and more of them.

But despite the bad news, there is a lot of good that can come from understanding your body’s reward system and how it relates to diet. Instead of being defeated by your brain, you can actually train it.

Dopamine and Diet

There are things you can do to train your body and brain to eat healthier. For one, do your damnedest to avoid those calorie-packed, super sugary, and generally bad foods. If you never eat them, your brain never gets the chance to associate them with the dopamine reward, thus making it so you don’t crave them. Resisting the initial temptation makes it easier to resist the temptation in the future, and instead of getting dopamine boosts from sugar, you’ll get them when you eat your healthy meals. Soon enough, your brain associates good food with dopamine rewards, and you’ll start to find yourself wanting to eat something healthy when you want a rewarding brain boost.

Eating smaller, more frequent meals, or meals with healthy snacks in between, can also help keep your brain feeling rewarded, and thus less likely to want those dopamine-boosting bad boys like sugar and sweets.

There are also nutritional elements that you can ensure are in your diet to make your body less dopamine-seeking, thus less craving of those unhealthy foods period. Research suggests that Iron, Vitamin B6, Folate and Vitamin E are key to maintaining healthy levels of dopamine and dopamine receptors in your brain, so you get the proper reward you deserve from your healthy meals, too. By keeping your brain dopamine-stocked at natural levels, you make it so you don’t need super stimulus like a Cinnabon to get the dopamine flowing.

Dopamine pathways in the brain thanks to flickr user mathplourde.

There’s also some research which suggests that Flavonoids, those lovely antioxidants found in berries and red wine, promote healthy dopamine neurons. So ensuring that you make room in your diet for some blueberries isn’t a bad idea, either.

Closing Note

Keep in mind that research into how exactly dopamine relates to eating – what we eat, how we eat, etc – is still very new. While we know quite a bit, new studies are released every day which increase our understanding of this incredibly complex system. It’s not a good idea, yet, to try to take any kind of dopamine supplement or drug for weight loss or management, as extreme excess dopamine can have devastating neurological effects. For that matter, direct dietary ingestion of dopamine is a fruitless endeavor, since dopamine itself can’t cross the blood-brain barrier.

In short, there’s no easy way out of this one: you have to just eat right, daily, to train your brain to enjoy it. It’s like exercise – you’re never going to get in shape without putting in the hours, no matter what the infomercials try to tell you. You won’t have a healthy, level and balanced dopamine system until you cut out the extremely-excessive calorie foods and eat healthy day in and day out. Eating a well rounded diet is the best way to make your body crave a healthy diet.

Previous posts in the Understanding Our Bodies series:

References:

Guilarte TR (1989). Effect of vitamin B-6 nutrition on the levels of dopamine, dopamine metabolites, dopa decarboxylase activity, tyrosine, and GABA in the developing rat corpus striatum. Neurochemical research, 14 (6), 571-8 PMID: 2761676
Duan, W., Ladenheim, B., Cutler, R., Kruman, I., Cadet, J., & Mattson, M. (2002). Dietary folate deficiency and elevated homocysteine levels endanger dopaminergic neurons in models of Parkinson’s disease Journal of Neurochemistry, 80 (1), 101-110 DOI: 10.1046/j.0022-3042.2001.00676.x
Martin A, Prior R, Shukitt-Hale B, Cao G, & Joseph JA (2000). Effect of fruits, vegetables, or vitamin E–rich diet on vitamins E and C distribution in peripheral and brain tissues: implications for brain function. The journals of gerontology. Series A, Biological sciences and medical sciences, 55 (3) PMID: 10795718
McGuire, S., Sortwell, C., Shukitt-Hale, B., Joseph, J., Hejna, M., & Collier, T. (2006). Dietary supplementation with blueberry extract improves survival of transplanted dopamine neurons Nutritional Neuroscience, 9 (5-6), 251-258 DOI: 10.1080/10284150601086134
Pleger, B., Ruff, C., Blankenburg, F., Klöppel, S., Driver, J., & Dolan, R. (2009). Influence of Dopaminergically Mediated Reward on Somatosensory Decision-Making PLoS Biology, 7 (7) DOI: 10.1371/journal.pbio.1000164
Arias-Carrión O, & Pŏppel E (2007). Dopamine, learning, and reward-seeking behavior. Acta neurobiologiae experimentalis, 67 (4), 481-8 PMID: 18320725
Radhakishun FS, van Ree JM, & Westerink BH (1988). Scheduled eating increases dopamine release in the nucleus accumbens of food-deprived rats as assessed with on-line brain dialysis. Neuroscience letters, 85 (3), 351-6 PMID: 3362423
de Araujo, I., Oliveira-Maia, A., Sotnikova, T., Gainetdinov, R., Caron, M., Nicolelis, M., & Simon, S. (2008). Food Reward in the Absence of Taste Receptor Signaling Neuron, 57 (6), 930-941 DOI: 10.1016/j.neuron.2008.01.032
Erikson KM, Jones BC, & Beard JL (2000). Iron deficiency alters dopamine transporter functioning in rat striatum. The Journal of nutrition, 130 (11), 2831-7 PMID: 11053528

Understanding Our Bodies: Amino Acids Are Important

nutrition — Mon, 20 Jul 2009 08:49:07 +0000

Just about every diet I know of supports eating a large portion of protein. Whether the strategy is to cut carbs or to cut fat or to cut calories in general, just about everyone agrees that protein is good for you. But why? And do the sources make a difference? What about protein makes it so important, and what do you need to include in your diet to reap the benefits?

Why Protein?

In biochemistry, there are 4 main types of compounds:

fats
carbohydrates
nucleic acids
proteins

They’re distinguished by their chemical structures. Proteins are compounds which are made up of amino acids, which all contain an amino (nitrogen-containing) and carboxyl (like carbon dioxide) group. Proteins are made when these amino acids are strung together and (often) folded into complex shapes. They can be structural proteins, like the keratin in our fingernails or the actin in our muscles, or they can be chemically functional, like enzymes. Proteins can also be very important in communication in the body – insulin, for example, is a protein. In fact, if you take away the water, 75% of our bodies are protein. All of these proteins require the right amino acids found in our bodies and our diets to be made. Watch this video to understand how they are made:

Can’t make amino acids. Still a cute guy though. Credit: Aaron Logan

While most microorganisms and plants can produce whatever amino acids they want, animals, including us, have lost the ability to produce certain amino acids. These amino acids are called the “essential” amino acids, or the ones we must intake in our diet. Without enough of a dietary source of these essential amino acids (of which, in humans, there are about 8, with 4 others needed by children), our bodies can have trouble making the proteins needed for ordinary functioning, and we can end up malnourished. On top of this, our bodies don’t store amino acids like they do fats or carbohydrates. To ensure we have the amino acids we need, we have to get them daily.

It would be easy to attain the amino acids we need if all we had to do was eat enough of them as needed to make proteins, but alas, as always, our bodies are far more complicated. As the body digests protein, a large portion of the amino acids that result are deaminated and are used for fuel instead of as protein building blocks. This is done by a two processes, either gluconeogenesis where proteins are converted to glucose directly or an alternate pathway where they are fed into the natural energy cycle (the citric acid cycle) at a later point to produce even less fuel. This particularly occurs under starvation conditions, where the body will actually start breaking down its own muscle and other protein sources for fuel. As far as energy goes, protein is a poor source of it, containing only 4 kilocalories per gram as opposed to the 9 in fats.

Our bodies don’t fluctuate in amino acid concentrations like they do with other molecules. Levels of amino acids in the blood are almost constant, regardless of diet. However, that’s not because diet isn’t important, it’s because the body will begin to attack itself and break down muscle and other tissue to keep amino acid concentrations level. This can be why some extreme dieters seem to lose weight but feel lethargic or unable to exercise – by massively cutting calories, they probably cut a lot of protein out of their diets, too, and their bodies are basically eating their muscle tissue to get amino acids for more essential uses like cell signaling. Therefore, to get the total amount of amino acids we need on a daily basis, we actually have to eat a high amount of excess amino acids.

When it comes to dietary intake, the weakest link is the most important. The most limited essential amino acid in our diet affects how well our bodies uptake the rest of them, so balance is key. In other words, whatever amino acid we’re most lacking in will set the bar for how our bodies intake all the others, and so to have healthy levels of all amino acids we have to have good balance and enough of each.

The Essentials and Our Diets

There are roughly 20 common amino acids, with 8 of them considered essential for adults and another 4 essential for children and infants. The essential ones for adults are:

isoleucine
leucine
valine
methionine
phenylalanine
threonine
tryptophan
lysine.

Additionally, cysteine, tyrosine, histidine and arginine are required by infants and young children. It’s rare that a person needs to supplement their diet with any form of pill or powder to get enough amino acids, and doing so can be dangerous if not closely watched. For example, body-building supplements contain a high concentration of the first three amino acids mentioned, but over time, extreme excess of these acids can lead to nerve degeneration or even liver and kidney toxicity. In general, extreme excess of any amino acid is bad for the body. It’s hard to get that kind of excess from eating – our bodies naturally just turn most excess deitary protein into fuel, but you can over-supplement.

Impact of Protein Deficiencies

Because of the many uses and importance of amino acids in our bodies, it’s key that we get enough and a balanced amount of the essentials, which is far more often the problem than excess amino acids. Protein deficiency is a huge medical issue in developing nations, with protein-energy malnutrition affecting 500 million people every year and killing 10 million of them. Severe cases tend to include complete loss of immune function and thus increased risks from other diseases. While it’s fairly rare in developed nations, protein deficiency can affect the poor and often occurs in those who are crash dieting to lose weight or in older adults, particularly leading to conditions like osteoporosis, as protein is key when it comes to bone health. Those recovering from surgery, trauma or illness can also be protein deficient if they don’t increase their dietary intake to match their increased needs. Our bodies use protein when we’re healing, so its important to eat lots of it when we’re sick or recovering.

Distended stomachs, a sign of malnutrition (thanks to Flickr user TKnoxB)

It’s even possible that protein deficiency is a far more common problem than we think, and that many simply suffer from very mild affects. There are studies which have shown lower protein intake in certain minorities. Some biologists, like Bob Lanier, a biology professor at Jesuit College Preparatory School of Dallas, have argued that a very slight protein deficiency might actually explain some of the variance in academic performance between poor minority and richer majority students. Since so much of brain function is tied to proper nutrition and protein intake, it’s entirely possible that even smaller changes in protein consumption, like that of crash dieters, could have an impact on mood and cognition, though few studies have looked deeper into this idea in adults. In children, however, a deficit in dietary protein as infants can have a marked affect on intelligence as older children, especially for boys.

How to Get Amino Acids

Steak could be the answer for your amino acids

Overall, adults require approximately 60 grams of protein per day, with higher intake required in pregnant and nursing women and, to a lesser extent, men, due to their higher overall muscle mass. Nutritionally speaking, food sources for protein are generally referred to as “complete,” as in containing all of the essential amino acids, or “incomplete,” as in only containing some essential amino acids. Complete protein sources include meat, fish, eggs and dairy products, while vegetables, beans and other plant products are considered incomplete. By far, meats are the best sources of complete dietary protein, but they also tend to be high in fat. Fish and poultry tend to be fantastic protein sources since they’re lower in fat and contain other, valuable nutrients.

This doesn’t mean, however, that you have to get all of your essential amino acids from meat, fish or dairy. Instead, a carefully balanced diet including a good variety of ‘incomplete’ sources can give you the full array of essential amino acids. For example, you can combine beans with brown rice, corn, wheat or nuts to get a complete set of amino acids. Also, soybean products like tofu and soymilk are complete proteins, so you can have a meat-less diet and still get plenty of dietary protein.

Eat Salmon!

The key is to eat 2 to 3 servings a day, or roughly 20 g per meal. If you get less in the morning, be sure to bulk up at lunch and dinner with lean meats or extra vegetables. And you have to eat protein DAILY, otherwise your body lacks the amino acids it needs for the day and begins to take them from places you might want them, like your sexy abs that you worked so hard for!

Previous posts in the Understanding Our Bodies series:

References:

Peng Y, Gubin J, Harper AE, Vavich MG, & Kemmerer AR (1973). Food intake regulation: amino acid toxicity and changes in rat brain and plasma amino acids. The Journal of nutrition, 103 (4), 608-17 PMID: 4693672
Müller O, & Krawinkel M (2005). Malnutrition and health in developing countries. CMAJ : Canadian Medical Association journal = journal de l’Association medicale canadienne, 173 (3), 279-86 PMID: 16076825
Bonjour JP (2005). Dietary protein: an essential nutrient for bone health. Journal of the American College of Nutrition, 24 (6 Suppl) PMID: 16373952
Lovejoy JC, Champagne CM, Smith SR, de Jonge L, & Xie H (2001). Ethnic differences in dietary intakes, physical activity, and energy expenditure in middle-aged, premenopausal women: the Healthy Transitions Study. The American journal of clinical nutrition, 74 (1), 90-5 PMID: 11451722
Lucas A, Morley R, & Cole TJ (1998). Randomised trial of early diet in preterm babies and later intelligence quotient. BMJ (Clinical research ed.), 317 (7171), 1481-7 PMID: 9831573

Understanding Our Bodies: Serotonin, The Connection Between Food and Mood

nutrition — Wed, 24 Jun 2009 08:55:35 +0000

Continuing the series on The Physiology of Nutrition, I present to you the connection between food and mood – serotonin. While it’s easy to see how what we eat has a direct impact on our waistlines, it seems a little foggier how our nutritional choices affect our brains. Even still, we all know intuitively how important food is to our emotions and our moods. After all, who hasn’t gotten angry or upset and wanted nothing other than a super-sizes sundae drizzled with chocolate sauce to calm down? We use food to affect our moods all the time without even thinking about it. But more importantly, our daily nutritional intake can have huge impacts on how we feel, and most of it is due to a little chemical called serotonin.

What is Serotonin?

Serotonin is a neurotransmitter which is highly common throughout nature. How it works is incredibly simple. Neurons (nerve cell) communicate by specialized areas of their cells called synapses where they are very close together. The first nerve cell dumps neurotransmitters into the space between, and the second nerve cell on the other side has receptors which recognize the transmitter and respond accordingly. Below is a basic picture of the scene where this exchange occurs:

How neurotransmitters help synapses fire (this is how your brain works!)

At the same time, as soon as the transmitter is dumped in between the cells, special proteins which are responsible for taking the transmitter back into the neurons start pumping, so the time that the transmitter is in between the cells is short. As the receptors recognize the neurotransmitter, they send signals inside the second cell which pass the signal onward and do whatever other physiological response that particular transmitter dictates. Soon enough, the first cell has all its signal back inside it, and the two neurons are back to their resting state, ready to signal again when the time is right.

A close-up of whats going on (serotonin is one of the white dots)

What is serotonin’s job as a neurotransmitter? It regulates signal intensity. Think of it like a volume control on a stereo: serotonin changes how efficiently neurons communicate with each other, making other signals louder or softer. Most often, it accompanies other transmitters, changing a neuron’s response to that particular signal. Because of this, its used by all kinds of nerve cells all over the body, and serotonin levels can dramatically alter our behavior. Levels too high can lead to sedation, whereas low levels are associated with debilitating psychiatric conditions and sudden infant death syndrome (SIDS).

Serotonin, The Necklace – by Molecule Muse

OK, if you pay enough attention to those annoying medical ads you probably have heard of serotonin. It’s one of the major mood neurotransmitters in our brains. When serotonin levels are low, we’re more depressed, and when they’re high, we’re happier. Many depression drugs target the serotonin system by attempting to artificially boost serotonin levels or sensitivity. MAOIs prevent the breakdown of serotonin in the body in general, thus artificially raising levels. Zoloft and other SSRIs (selective serotonin re-uptake inhibitors) target the serotonin system by blocking the those pumps which bring the serotonin back in after a signal, causing signals to seem stronger and last longer. For that matter, recreational drugs often target serotonin as well. Mescaline, LSD and other psychedelics mimic serotonin and activate serotonin receptors in the brain. Ecstasy’s main component, MDMA, causes your brain’s neurons to release stored serotonin, causing the happy, euphoric state the drug is named for.

Serotonin in the Gut

But what you probably don’t know is that about 80 to 90 percent of the human body’s total serotonin is found in specialized cells in our guts, not in our brains. In fact, serotonin was tied to food long before it became an important mood hormone. In many species, its directly tied to appetite – deplete serotonin, and they act like they are starving. They hunt for food, put off mating and egg laying, and generally do whatever they can to find another bite to eat.

In many species, including us, serotonin is key in the functioning of gut muscles, causing contraction of our intestines. As it turns out, our digestive system has its own neural network and largely controls itself without any input from our brains whatsoever. In fact, if you were to cut the main nerve that connects the two, the gut would continue to function independently. In part, that is where serotonin comes in. It is key in the control our digestive muscles during digestion. Serotonin acts on gut nerves which signals pain, nausea and other gut problems.

Stomach, up close

For example, if you eat something that upsets some of your stomach cells, they release copious amounts of serotonin. This flood of neurotransmitter causes the gut to empty, leading to diarrhea. But if the serotonin overflows the gut’s management system, it leaks into the blood, where it stimulates 5HT3 receptors in the brain which induces vomiting. So depending on how bad the insult to your stomach, serotonin levels control how your body reacts. Because of this, some of those anti-depressants, particularly the SSRIs, frequently trigger nausea and vomiting as a side effect.

Our gut uses so much more serotonin than our brains its amazing. In fact, so much serotonin enters our stomachs every day that if it were injected into the body in general it would be lethal. Luckily for us, there are certain gut cells which contain a lot of serotonin transporters which keep the serotonin in our stomachs and out of the rest of our bodies. (Watch the following video if you REALLY want to know the science behind serotonin in the gut):

There’s even rising evidence that serotonin is important in our hunger signaling, particularly in feelings of fullness. Injecting low serotonin doses into the body has caused rats to eat less even though they’re hungry, an effect enhanced by those same MAOIs that increase serotonin levels. Overall, more and more research suggests that serotonin is somehow modulating food intake – but we’re not sure exactly how… yet.

Serotonin and Nutrition

Since it has so many diverse and important roles in the body, serotonin levels are key to health mentally and physically. Because its so common in all kinds of animals, serotonin can be found in a variety of foods. The highest concentrations are found in:

walnuts
plantains
pineapples
bananas
kiwis
plums
tomatoes

These foods can boost serotonin levels in the gut, ensuring rapid communication between gut cells. But because serotonin in its complete form cannot pass through the blood-brain barrier, we have to do more than include serotonin-rich foods in our diets: we have to include its building blocks.

In fact, our bodies naturally understand this, and cause us to crave foods rich in tryptophan, an amino acid key to serotonin production in our brains when serotonin levels are low. What foods are high in tryptophan, you might ask? Carbohydrates. All of a sudden those calorie-rich, carbohydrate-packed comfort foods make a whole lot of sense. It’s logical, then, that sad people tend to eat more junk food even when a more nutritious option is available. When we’re depressed or upset, we want higher levels of serotonin to feel better, and packing in as much tryptophan as possible is our body’s way of trying to cope. Studies have shown that ingesting carbohydrates boosts serotonin synthesis and levels. Particularly tryptophan-rich foods include:

turkey
bananas
milk
yogurt
eggs
meat
nuts
beans
fish
a variety of cheeses including Swiss and Cheddar

The irony is that not only does mood affect how we eat, but how we eat affects our mood. It’s a two way street. Research has shown that dieters tend to become depressed about two weeks into a diet, about the time their serotonin levels have dropped due to decreased carbohydrate intake. Cutting calories has been shown to reduce tryptophan levels in rats, leading to less serotonin , and even decreases the number of receptors in their brains, so they’re less responsive to the serotonin they have.

Watch out ladies…

Of course, just because that’s how the world seems to work, women have to be even more careful than men when it comes to dieting and serotonin. In women, calorie reduction has a dramatic impact on serotonin and tryptophan levels – an effect not nearly as strong in men. This strange double standard is suggested to be a part of why women are so much more prone to eating disorders. The obvious recourse when it comes to dieting, logically, is that by cutting calories we make ourselves more depressed, which in turn makes our bodies want more carbohydrates and calories to boost our moods. It’s yet another reason our weight tends to yo-yo when we try to diet, especially when carbs are cut, and helping keep serotonin levels in check might just be the solution. For example, cheat. Giving yourself a carb-rich treat every so often can help you maintain higher serotonin levels and keep you in a better mood where you can curb your cravings to eat calorie-craving comfort foods during the rest of the week.

But its not just tryptophan that’s important. It turns out that vitamin levels in our diets can have a dramatic impact on serotonin systems. One of the most important vitamins key to serotonin function is thiamine, one of the components of Vitamin B Complex. Simply altering the levels of thiamine in our diets and ensuring enough intake can have amazing effects. One study, for example, found that supplemental vitamins for a year significantly boosted women’s moods and overall well-being, particularly due to levels of thiamine.

Another Vitamin-B compound, folic acid, is also strongly linked with serotonin levels. Boosting folate levels in older people, who are generally deficient compared to younger adults, has been found to improve their mood and cognitive function. Even in healthy adults higher levels of serum folate have been linked to fewer mood swings and negative moods. And even more impressively, high folate levels can improve other depression treatments, particularly with how well anti-depressants work. Exactly how folate relates to serotonin is unclear, though it appears to act through an intermediate compound called S-adenosylmethionine (SAM). SAM increases serotonin levels, but it requires folic acid. Folic acid deficiency leads to low levels of SAM, and subsequently reduced serotonin.

Serotonin and Behavior

One way in which we can help our bodies have healthy serotonin levels is by good behavior. Things we do, behaviorally, have a major impact on serotonin levels. For example, stressing, feeding, and exercise have been shown to have marked affects on serotonin levels in rats. It turns out that sleep and exercise are particularly strongly tied to serotonin. After all, one of serotonin’s major actions in our bodies is as a sedative, so its not shocking that it has close ties with how we regulate our energy.

Exercise to increase serotonin (credit, Frederic de Villamil, flickr)

It’s well established that exercise can boost our moods and make us feel better. One way in which this occurs is by increasing serotonin. Exercise is a cheap and dirty way to boost blood and brain serotonin levels immediately, making it a good alternative to other ways of dealing with stress and depression. But exercise does even more: it helps regenerate neurons. Unlike we’re told when we’re young, our brain cells can and do regenerate, albeit slowly. Increased levels of exercise have been shown to increase neuron production, giving out brains better ability to utilize the serotonin boosts and improve our moods. Exercise also allows our brains cells to function better by making them more flexible, leading to better responses to all neurotransmitters, including serotonin.

Sleep, however, is even more important when it comes to serotonin. People have been studying the connection between serotonin and sleeping behaviors for over 50 years. We know that changes in serotonin levels have marked impact on sleeping, with decreases in serotonin leading to apnea or other sleep problems. But only recently have we realized the opposite is true, too. Lack of sleeping negatively affects our brains neuronal signaling, including how it responds to serotonin. Sleep deprivation has been shown to desensitize serotonin pathways, meaning that consistent lack of sleep has a negative impact on our brain’s response to serotonin in general. This means that consistent healthy sleeping patterns are key to maintaining healthy serotonin signaling in our brains and likely our bodies in general.

Go Outside and Be Happy! Light triggers serotonin…

Another, simple way to increase serotonin production is to get outside. Scientists discovered the connection between light and serotonin almost accidentally. They looked at levels of serotonin in recently-dead people, and found higher concentrations of serotonin in those who died in the summer instead of the winter. That got doctors thinking. It was already known that many people have seasonal changes in mood, with more depression occurring during the cold, dark winter than the warm, sunny summer. It had even been found that increasing light levels helped treat non-seasonal depression. Could light be having an impact on serotonin levels? Research suggests yes. They’ve since found that serotonin levels in healthy men are directly correlated to the amount of sunlight in the day, with marked increases as the seasons changed and the sun’s intensity rose, and other research has found strong connections between light and serotonin function. Taken together, these suggest that a walk in the sun or getting away on vacation to somewhere tropical and sunny during the darker months might be able to naturally boost serotonin levels.

There are other behavioral ways to change serotonin levels, too. Rising evidence suggests that our own emotions and moods affect serotonin levels. In other words, trying to boost our moods or rosy our outlooks can help raise serotonin levels. Things you can try:

Meditation
Relaxation Techniques
Talking to Friends
Counseling

All these mood-boosting behaviors might just help raise overall serotonin levels, allowing us to keep out of those bad moods later on.

In The End…

Of course, like anything else, it’s balance that counts. Over-eating of carbohydrates and sugars can lead to decreased sensitivity to serotonin, leading to negative mood and physical side effects like obesity. Eating lots of protein can help balance serotonin levels. As it turns out, eating protein before carbs curbs the usual spike in serotonin. And, the truth is, we want to cut down our serotonin sometimes. It is a mild sedative, and eating serotonin-boosting foods in the middle of the day can make us drowsy and less focused. A protein-rich snack instead will help increase energy and keep you going when you need it most.

Even worse, eating too serotonin-boosting foods, while it might feel good for a short time, can lead to a worse crash later on. That’s why a candy bar or a soda are so much worse for us – the sugary energy-upping effect is only temporary, and we’re left with sleep-inducing increases in serotonin instead, leading to a much harder crash. Proper nutritional balance is required for sustained energy throughout the day and a balanced mood. And if you do want a snack with a pick-me-up in terms of mood, try something with less sugar or caffeine but plenty of tryptophan, like nuts – plus nuts are packed with other brain-boosting goodies, too.

In general, though, people don’t get enough of the healthy serotonin boosters in our diets – leading to a lot of grumpiness and overall blah-feelings. We are outside less than we should be, sleeping odd or too few hours, exercising less, and generally eating poorer. All of these are causing our bodies serotonin levels to get out of whack. Understanding the impacts of our actions and what we eat on this important system can help us improve our moods and gut health dramatically without resorting to anti-depressants or other drugs and their side effects, allowing a natural way for us to feel great more often.

You may want to check out the first part of the series if you enjoyed this amazing article: Leptin, The Fullness Hormone

References:

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Garattini S, Bizzi A, Caccia S, Mennini T, & Samanin R (1988). Progress in assessing the role of serotonin in the control of food intake. Clinical neuropharmacology, 11 Suppl 1 PMID: 3052823
Fernstrom, J., & Wurtman, R. (1971). Brain Serotonin Content: Increase Following Ingestion of Carbohydrate Diet Science, 174 (4013), 1023-1025 DOI: 10.1126/science.174.4013.1023
Haleem, D., & Haider, S. (1996). Food restriction decreases serotonin and its synthesis rate in the hypothalamus NeuroReport, 7 (6) DOI: 10.1097/00001756-199604260-00011
Anderson IM, Parry-Billings M, Newsholme EA, Fairburn CG, & Cowen PJ (1990). Dieting reduces plasma tryptophan and alters brain 5-HT function in women. Psychological medicine, 20 (4), 785-91 PMID: 2284387
Goodwin GM, Fairburn CG, & Cowen PJ (1987). Dieting changes serotonergic function in women, not men: implications for the aetiology of anorexia nervosa? Psychological medicine, 17 (4), 839-42 PMID: 3432460
Wurtman JJ (1993). Depression and weight gain: the serotonin connection. Journal of affective disorders, 29 (2-3), 183-92 PMID: 8300977
Benton, D., Haller, J., & Fordy, J. (1995). Vitamin Supplementation for 1 Year Improves Mood Neuropsychobiology, 32 (2), 98-105 DOI: 10.1159/000119220
Alpert M, Silva RR, & Pouget ER (2003). Prediction of treatment response in geriatric depression from baseline folate level: interaction with an SSRI or a tricyclic antidepressant. Journal of clinical psychopharmacology, 23 (3), 309-13 PMID: 12826993
Williams, E., Stewart-Knox, B., McConville, C., Bradbury, I., Armstrong, N., & McNulty, H. (2007). Folate status and mood: is there a relationship? Public Health Nutrition, 11 (02) DOI: 10.1017/S1368980007000031
Resler G, Lavie R, Campos J, Mata S, Urbina M, García A, Apitz R, & Lima L (2008). Effect of folic acid combined with fluoxetine in patients with major depression on plasma homocysteine and vitamin B12, and serotonin levels in lymphocytes. Neuroimmunomodulation, 15 (3), 145-52 PMID: 18716414
Rueter LE, & Jacobs BL (1996). A microdialysis examination of serotonin release in the rat forebrain induced by behavioral/environmental manipulations. Brain research, 739 (1-2), 57-69 PMID: 8955925
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Understanding Our Bodies: Leptin (The Fullness Hormone)

nutrition — Tue, 09 Jun 2009 08:58:36 +0000

Time and time again, I tell you guys that the best way to stay healthy is to stay informed. Read labels, I say. Know what you’re eating. Know what you’re not eating. Know this, know that, etc and make informed decisions. Well, part of making informed decisions is understanding how your body works. And for that reason, I’ve decided to dive into a bit of physiology.

Even informed consumers tend to know very little about how their appetites actually work. What makes you hungry or full? Why do some foods fill us up more than others? What exactly is going on in our bodies, anyway?

I figured you just might want to know. So here is part one of a new series I call “Understanding Our Bodies” – nutrition based on how our bodies work. And to kick it off is a little explanation of the fullness hormone: Leptin.

What is Leptin?

Leptin is a hormone that is tied closely to regulating energy intake and expenditure, including appetite, metabolism and hunger. It is the single most important hormone when it comes to understanding why we feel hungry or full. When present in high levels, it signals to our brain that we’re full and can stop eating. When low, we feel hungry and crave food. It does this by stimulating receptors in our hypothalamus, the part of our brains which regulates the hormone system in our bodies. When leptin binds to receptors in this part of our brains, it stimulates the release of appetite-suppressing chemicals. People with leptin disorders eat uncontrollably.

Your leptin LEVEL is high when you are full, low when you are hungry

Now here’s the strange part. Leptin is produced mostly by our adipose tissue – aka our fat. The level of circulating leptin is directly proportional to the total amount of fat in the body. That means the more fat you have, the greater the amount of leptin you have. It may seem counter-intuitive, but it makes sense in the end when we consider how yo-yo dieting tends to be. It takes some time for your body to adjust to large changes in body fat levels when it comes to leptin.

The total AMOUNT of leptin you have is related to your weight

So when you lose a lot of weight quick, via liposuction or serious calorie restriction, your leptin levels plummet. Subsequently, you get hungrier, your thyroid decreases output and your metabolic rate drops. Your body then increases catabolic hormone activity and appetite, making you tend to slip off your regime and gain all that weight right back. That’s why crash diets are often ineffective – your leptin won’t let you eat less, and even if you do, you’re lethargic and your metabolic rate slows way down.

Of course, just because it makes things difficult for dieting, leptin levels are far more sensitive to starvation than overeating. So when you cut caloires and start ot burn fat, the leptin levels in your body plummet, but when you eat too much they don’t skyrocket – although they do increase. Leptin levels increase with increased insulin levels, like right after eat, and when our body is storing energy. Keeping this in mind, in general, can help you eat healthier and loser weight in the long run.

The Science of Leptin

Obviously, since leptin is so key to hunger and feeling full, scientists have been looking into it as a possible target for anti-obesity or weight loss. As it turns out, leptin controls a lot more than just our feelings of fullness.

Turning on leptin in the brains of mice causes them to exercise more, according to research from Harvard Medical School. It’s interwoven into how our bodies control our metabolism, activity levels, and energy budgeting – like immediately increasing appetite when fasting. While levels drop quickly, eating can bring them back up, too. It has been shown to reduce lipids in muscle and other tissues which lead to insulin resistance (the first step towards type 2 diabetes). It even controls what foods we find appealing when we’re just looking at them. Basically, it seems like the perfect way to lose weight – just give people more leptin, right? Well, there is another factor at work.

Leptin Resistance

But when researchers gave people leptin in human clinical trials, people didn’t lose weight. The trouble is, your body constantly tries to adjust basal leptin levels. If there’s a lot of it all the time, like in obese and overweight people, the brain loses sensitivity. Mice can become leptin resistant after as few as 3 days of overfeeding – so it happens quickly in response to consistent high blood glucose levels.

When obese, your leptin LEVELS spike radically because you have higher leptin AMOUNTS in your body (causing leptin resistance in the brain)

When it does this, it takes more and more leptin before our bodies feel full. When we get fatter, our bodies produce more leptin, and we become resistant to it. So obese people actually have unusually high leptin levels, but are not responsive to it. Even when healthy people eat a much lower calorie diet for a little while, levels decrease, and they feel hungrier and less energetic, even if they haven’t lost weight yet. To lose weight and keep it off, you have to give your body time to adjust to the new, lowered leptin level, so it sets that as “normal” and you feel full when you’re supposed to.

Yes, he is.

The bad news is that not just excess weight can lead to leptin resistance. A new study published in the American Journal of Physiology found that high fructose diets can induce leptin resistance. These sugars actually impair the leptin’s ability to cross the blood-brain barrier and reach the hypothalamus. So even when the leptin levels are high, not enough is reaching the brain to tell the body to stop eating.

How do you use this information to lose weight or keep healthy?

First things first: quit the crash diets. You aren’t going to do your body any favors by losing weight too quickly. If you are trying to lose weight, though, there’s one thing you can do to help your body out: cheat. Seriously.

When you cut calories dramatically, your body acts like its starving and your leptin levels plummet. You’ll be hungry and generally have lower energy levels and want to eat more. So, once a week or so, cheat. Really cheat. Have a nice, high-calorie meal.

Your body then senses the rush of fuel and boosts leptin levels, increasing your metablism and priming your body for fat loss. Cheating helps ease your body down to lower daily leptin levels without making it feel too starved. That way, as you lose the weight, your body adjusts and realizes that the reduced leptin levels are normal not starving. And you get to enjoy something delicious – come on, it’s a win-win!

A beautiful sockeye salmon

Secondly, avoid too much sugar intake. High calorie loads aside, the sugars make your brain less sensitive to leptin, which causes you to eat more and pack on the pounds. Conversely, some foods have been shown to increase leptin activity and sensitivity. The biggest connection scientists have found is between Omega-3 Fatty Acids and leptin. That’s right – the ever remarkable fish just keep getting better and better. Researchers found that a group of people who ate a high proportion of fish every day had lower leptin levels despite eating the same calorie loads and having the same body fat as their fish free cousins – suggesting that a fish-rich diet increased their bodies’ sensitivity to leptin.

There’s good news, too, for those that are already overweight and leptin resistant: it’s only temporary. Research has shown that reducing fat content in leptin-resistant, obese mice allowed them to regain leptin sensitivity. So even if you’re overweight and likely leptin resistant, you can improve on that state. Unlike type 2 diabetes and insulin resistance, which is very hard to reverse, leptin resistance is fairly correctable with a normal, healthy diet and exercise.

And lastly, there’s something really simple that everyone can do to keep their leptin levels high and keep cravings under control: sleep well. When you go to sleep, your leptin levels naturally rise – after all, you want to be sleeping, not snacking, so your body knows to cut down on your hunger while you’re resting. But if you cut your sleeping short, your body tries to adjust by making you hungry again. Research has found that shorter sleep periods (6 hours or less instead of lower overall daily leptin levels, cause an increase in appetite, and even make people crave carbs and other fattening foods. So its important for your body to rest well to maintain its natural hormonal balance, allowing you to look and feel your best.

In summary:

Stop crash diets
Eat ONE large meal per week to spark leptin-based weight loss
Avoid processed sugar
Eat Omega-3 (in fish/flaxseed/walnuts)
Sleep well

Like any other system in our bodies, the our hormonal appetite controls are sensitive to our daily habits and routines. The better a routine you have – sleeping well, eating right, and exercising, the more balanced your system will be and the better you will feel.

Stay tuned for more deep dives into the physiology of nutrition with the next installment of Understanding Our Bodies!

References:

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