Recently, the U.S. Department of Agriculture and Health and Human Services issued their new preliminary guidelines for improving the nation’s diet. The major recommendations haven’t changed since the last ones issued five years ago, and include limiting sugar, saturated fats, and salt. Many people find it somewhat easy to cut back on sugar and saturated fats if they try, but reducing sodium intake has remained a problem for even people who try hard to eat better.

It turns out that some people have more trouble than others, and it’s not just a question of willpower. Our genetics influence some of the difference in the levels of salt we like to eat.

Where does the salt in our diet come from?

Americans consume 3,400 milligrams of salt a day on average. That’s more than double the 1,500 milligrams recommended by the new USDA/HHS guidelines and other groups like the American Heart Association and the Institute of Medicine.

Salt (otherwise known as Sodium Chloride), occurs naturally in many foods, but we also add it to our diets directly. Here’s a pie chart which shows where the salt comes from in the average American’s diet:

Pie Chart explaining where sodium comes from in our diets

Image from the Risk Factor Monitoring and Methods Branch Website, part of the Applied Research Program of the National Cancer Institute. Updated January, 2010. Accessed June 18th, 2010.

In general, most people could benefit by reducing the sodium intake in their diets. But some people find this much harder than others – the question is: why?

Are We Hardwired to Prefer Salt?

By and large, most people prefer saltier versions of foods. How each of us perceives the “saltiness” of a given amount of salt, though, varies widely.

Studies have found that this variation could stem from innate differences in how our tastes function. One of the best-studied markers of how tastes vary is the perceived bitterness of propylthiouracil (PROP). Researchers call people with high sensitivity to PROP “supertasters,” as they are more sensitive to small changes in a number of different tastes. Supertasters are also more likely to eat more salt in their diets. People who are more sensitive to PROP, finding even small amounts bitter, are more sensitive to changes in saltiness, and need higher levels of salt to make bitter foods taste more palatable. PROP sensitivity, as it turns out, is strongly genetic, which would mean we have little control over how bitter or salty foods taste.

But others have suggested that cultural, behavioral or otherwise non-genetic factors are to blame for a person’s relative sensitivity and addicted-ness to salt. The idea is that a taste for salt could be explained by how much salt was eaten as a child or emotional attachments to salty foods. By eating more salt during development, people can influence how they perceive foods later in life.

As the research continues to pile up, though, it seems more and more likely that genetics play a large role in our preference for salt. A study just published in Physiology and Behavior analyzed the PROP sensitivity argument using 87 people. They found, like previous research that some preferred saltiness more than others and needed that salty flavor to make bitter foods taste better. The more sensitive a person was to PROP, the more salt they preferred and ate in their diets. More importantly, these supertasters which preferred salt weren’t adding it to their foods, they were simply eating more in their diets. This means that they might not realize how much salt they are consuming overall, since they aren’t pouring the salt on at the table, so they may believe they’re not eating as much salt as they really are.

Doomed By Our Genes?

The bad news is that our desire for salt may be largely genetic. The good news, though, is that this doesn’t mean you can’t eat healthier and reduce your salt intake. The reason behind the pension for salt in some people is that is helps alter bitter tastes. So, if you avoid bitter tasting foods, you can help avoid the desire for extra salt. Take a look at the chart describing salty foods, and think about what you eat of it. Anything you can do without will help cut your salt intake. Do your best to keep an eye on the amount of sodium you eat, and if you do, you’ll find that you can cut back in little ways that add up without sacrificing the flavor of foods.

Chang WI, Chung JW, Kim YK, Chung SC, & Kho HS (2006). The relationship between phenylthiocarbamide (PTC) and 6-n-propylthiouracil (PROP) taster status and taste thresholds for sucrose and quinine. Archives of oral biology, 51 (5), 427-32 PMID: 16297856

Hayes JE, Sullivan BS, & Duffy VB (2010). Explaining variability in sodium intake through oral sensory phenotype, salt sensation and liking. Physiology & behavior, 100 (4), 369-80 PMID: 20380843