Under the Microscope: The Nutrition - Gene Connection

Victoria Shanta Retelny, R.D., L.D.N.

What if you had a personal profile of which foods were best suited to your genetic makeup to keep your genes disease-free for life? Food can act as medicine -- or wreak havoc on the body -- depending on the nutrients and on the person eating them. Blueberries are heart-healthy, tomatoes protect the prostate and fish is good for the brain -- but only for certain people. When it comes to how the body processes nutrients, each person's unique genetic makeup determines how their cells respond to what they eat. Genes can explain a number of nutritional phenomena, such as why some people can adhere to a low-saturated fat and high-plant food diet, yet still be prone to high blood cholesterol levels.

"The complete diet is a complex matrix of food components, often supplemented with herbals, botanicals and dietary supplements containing bioactive components, vitamins and minerals," explains Stephan Barnes, Ph.D., professor at the University of Alabama. If every human being ate and drank the same foods every day, there would still be a variety of health outcomes. Why? "There are differences in our individual genomes," says Barnes. This is precisely why moving away from the current medical model -- which favors treating health issues with a one-size-fits-all mindset -- and focusing on personalized gene-diet interactions is an important public health agenda item.

A personal profile of which foods best match your genes may not be far off. Now that scientists understand how the collective human genome looks and varies, large studies are examining the genetic basis of health and chronic disease. Nutrition has become a significant part of genetics study. Gene-diet interactions may help people select foods that lead to optimal health or reduced risk of chronic diseases, according to a March 2009 article in the Journal of the American Dietetic Association (JADA).The food-gene relationship. How does the gene-diet theory work? Every human being's genetic code varies -- there are about 10 million individual genetic differences, also called "single nucleotide polymorphisms" (SNPs). Emerging science has discovered that nutrients can affect SNPs by preventing or promoting disease. We now also know that your genes are not necessarily your destiny, especially when it comes to diet-related diseases, according to a recent commentary in JADA by Ruth DeBusk, Ph.D., R.D., a geneticist and clinical dietitian in Tallahassee, Florida. The study of nutrition combined with genetics -- also called nutritional genomics or nutrigenomics -- offers insight into ways people can tailor their diets to more closely fit their unique genetic makeup, describes DeBusk.

Genes and functional foods

Functional foods like omega-3s from fish, flaxseed and walnuts, and epigallacatechin-3-gallate (EGCG), the compound in green tea, are under study for their effect on gene activation and disease prevention.

For some people, eating more omega-3 fatty acids decreases the risk of certain diseases, such as cancer and cardiovascular disease, and even delays death; but for others with a different genetic makeup, omega-3s may offer no effect on health. These are the findings from an analysis of 48 randomized controlled trials and 41 cohort studies published in a 2006 issue of the British Medical Journal. Among the subjects in these 89 studies, omega-3s did not play a significant role in overall health. Genes may be the reason for this, according to a synopsis of these findings published in JADA in March 2009 by Lynnette Ferguson, D.Phil., D.Sc., a faculty member at the University of Auckland, New Zealand. The researchers in these omega-3 studies did not account for genetic variation, Ferguson says, meaning that some people may have gene types that allow omega-3s to work effectively in the body but others with different gene types may not benefit from this important fat.

In the case of green tea's nutrient, EGCG, data links it to cancer prevention, specifically in women at high risk for breast cancer. Once again, genes come into play. In the Singapore Chinese Health Study published in August 2005 in the journal, Carcinogenesis, researchers found that women with the gene type for higher risk of breast cancer reduced their breast cancer risk by one-third when they drank more green tea (and thus consumed more EGCG). However, there's a genetic catch: The women with the low-risk gene type for breast cancer showed no benefit in breast cancer risk from drinking more green tea. These findings can be attributed to a gene-diet interaction.

The relationship of genes to nutrition is "complex detective work," according to Dr. Barnes. "The future is immense; we've only just started. Eventually there will be integration with the efforts to define person-to-person genetic and genomic variation," he explains.

The obesity-gene connection

Hundred of genes have been associated with obesity, according to a January 2007 article in the journal, Epidemiological Reviews. However, both genetics and environment play a strong role in obesity. Researchers have studied how fat cells interact with one another and their environment. They have determined that fat cells are not loners; they communicate with each other, as well as with what is around them. As a result, fat cells can affect their environment and contribute to the onset of chronic diseases.

Defects in genes have been found to contribute to obesity, as well as related diseases like type 2 diabetes, heart disease, hypertension and cancer. Obesity typically breeds multiple genes that interact with environmental factors -- such as a lifestyle of overeating or not exercising -- over the course of time. So obesity becomes an environmental influence on type 2 diabetes and vice versa. A perfect example of this conundrum is insulin, the hormone that regulates blood sugar. If the body has too much circulating insulin, it can lead to an increase in fat storage and weight gain, but without enough insulin the body will not be able to get blood sugar into the cells for energy, which can lead to the onset of type 2 diabetes.

If your mother or father is obese, does that mean you will be? Probably, since obesity has a strong familial component. According to early obesity research in the New England Journal of Medicine, identical twins were found to be more alike in body weight than fraternal twins, and adopted children's fat percentages fell in line with their biological parents' rather than the adoptive parents'. From a genetic standpoint, the tiniest malfunction in the receptor for leptin, a hormone that makes us feel full, can result in overeating and morbid obesity. The promising news is that lab tests can identify if hormones, like leptin, are off balance and treatments can be prescribed.

The bottom line on gene-food interactions

We know that proper nutrition and lifestyle behaviors play a role in diet-related disease prevention, but combine that with the detection of genetic variations and more targeted interventions and the possibility of vastly improving health -- for individuals, as well as populations -- becomes limitless. As scientists continue to explore the exciting field of nutrigenomics, keep in mind that in the meantime, eating a balanced diet and maintaining a healthy body weight is still the best line of disease defense, regardless of your genetic profile.

NEWS & CURRENT EVENTS ...

Health - Under the Microscope: The Nutrition - Gene Connection