You are what you eat, or so the saying goes. But a new generation of molecular biologists is starting to give that old adage a decidedly high-tech twist. By combining the latest discoveries in human genetics with a deeper understanding of the hundreds of compounds found in food, investigators have begun to tease apart some of the more complex interactions between your diet and your DNA. In the process, they hope eventually to give consumers more personalized advice about what to eat and drink to stave off heart disease, cancer and other chronic conditions of aging. "We are trying to put more science behind the nutrition," says Jose Ordovas, a geneticist at the Friedman School of Nutrition at Tufts. "We want to finally understand why nutrients do what they do and to whom--why a low-fat diet may not work for some but works for others."
Do you drink three cups or more of coffee a day? Genetic tests can now determine whether you--like approximately 10% to 20% of the population--have a specific genetic variation that makes it harder for your body to absorb calcium in the presence of caffeine, thus increasing your rate of bone loss.
Are you getting enough folic acid, found in beans, peas and fortified grains? Researchers have learned that many people have a genetic predisposition that puts them at greater risk of developing heart disease because they need more folic acid than the average person to maintain normal blood chemistry.
Would a high-fat diet be particularly damaging to your health, given your genetic makeup? About 15% of folks are born with a form of a liver enzyme that causes their HDL, or good cholesterol, level to go down in response to dietary fat. In most people the HDL level goes up, counterbalancing some of the bad effects of dietary fat on LDL--the dangerous cholesterol.
This area of research is so new, there's still a bit of a debate over what exactly to call it. Nutritional genetics? Nutritional genomics? Nutrigenomics? But by any name, the field is growing fast. Indeed, some start-up companies simply aren't waiting for all the scientific mysteries and subtleties to be worked out and have begun to offer tests for a limited number of gene-nutrient interactions directly to consumers.
None of those genetic variations are immediately life threatening. In fact, most of them have no apparent effect. The variants are not like the mutations most of us learned about in school--alterations that cause entire genes or series of genes to malfunction and that result in diseases like sickle-cell anemia and cystic fibrosis. Instead the changes nutritional geneticists are looking for are more like normal variations in the correct spelling of a word--say, theatre or theater, depending on whether you speak the Queen's English or American. "We all have these variants in our genes," says Ray Rodriguez, a geneticist at the University of California at Davis. "And they affect how we absorb, utilize and store various nutrients."