ATLANTA ( CNN ) -- To a degree some may find hard to swallow , science is proving the old adage `` you are what you eat . '' Americans eat corn in the form of chips but also consume it in the ubiquitous high fructose corn syrup . Proteins and fats in your food are incorporated into your body and brain with potentially profound effects on your health and even your behavior . Todd Dawson , a plant biologist at the University of California-Berkeley , can test a strand of hair to determine how much corn is in your diet or mine by looking for a form of carbon found in corn . `` We are what we eat with respect to carbon , for sure . So if we eat a particular kind of food , and it has a particular kind of carbon in it , that 's recorded in us , in our tissues , in our hair , in our fingernails , in the muscles , '' Dawson says . Dawson tested a strand of my hair : 69 percent of the carbon came from corn . This may seem high , but it is typical for Americans . `` We 're like corn chips walking because we really have a very , very large fraction of corn in our diets , and we actually ca n't help it because it 's an additive in so many of the foods we find on the market shelves , '' Dawson says . Foods like ketchup , salad dressing , soda , cookies and chips all contain corn , usually high fructose corn syrup . `` I think where the danger comes in with corn is that much of the corn grown now in North America is going into making high fructose corn syrup , '' Dawson says . `` So it 's not that corn per se is bad , but it 's the sweetener made from corn that gets into many of the foods that Americans are probably consuming too much of , and we now see that showing up as obesity and heart disease and potential for type 2 diabetes . '' To be fair , researchers say we 're eating too much of all kinds of sugar , not just high fructose corn syrup . And the Corn Refiners Association points out that `` many parts of the world , including Mexico and Europe , have rising rates of obesity and diabetes , despite having little or no high fructose corn syrup in their foods and drinks . '' Europeans eat a diet with far fewer processed foods and corn-based sweeteners . Dawson tested his own hair after three months in Italy : 5 percent corn . Americans also eat an extraordinary amount of soybean oil , another key ingredient in most processed foods . Checking labels during a recent trip to the grocery store I found soybean oil in everything from tortilla chips to fruit syrup . Dr. Joseph Hibbeln at the National Institutes of Health estimates that soybeans , usually in the form of oil , ­ account for an astonishing 10 percent of our total calories in the United States . In recent years , a form of soybean oil has been the primary source of trans fats , which raises levels of LDL , or bad cholesterol , in our bodies and is thought to contribute to heart disease . Our bodies need a balance of omega-6 fatty acids like soybean oil and omega-3 fatty acids like fish oil , Hibbeln says . Over the last century , our diets have shifted almost completely to omega-6 fatty acids . `` It 's quite likely that most of the diseases of modern civilization , major depression , heart disease and obesity are linked to the radical and dramatic shift in the composition of the fats in the food supply , '' Hibbeln says . Our brains are composed of fatty acids , and an absence of omega-3 fatty acids can actually change our behavior , according to Hibbeln . Hibbeln 's research suggests diets containing omega-3 fatty acids found in fish reduce depression , aggression and anger , while improving mental well-being . Quite literally , food for thought . E-mail to a friend .
Biologist : 'We 're like corn chips walking ' Soybeans account for 10 percent of calories in U.S. , NIH doctor says . More omega-3 fatty acids in diet can improve mental health , he says .