Gene Tests and Gene-Diet Interaction

Friday, August 17, 2007 - 1:19pm

By Donna Feldman, MS, RD

You've personalized your ring tones, your screensaver on your laptop, and your stationary. You will soon be able to add your diet to that list of customizable items. However, the process won't be quite as quick or simple as a 10-second download, but the promised benefits should be well worth the extra effort.

Genes and health

You probably have at least a basic understanding of genes, those sequences of DNA that control every structure and process in your body. While the basic set of genes that control one characteristic (say eye color) are organized the same for everyone, little differences in the DNA sequence give one person brown eyes and another blue. Likewise, the genes that control how you utilize a certain vitamin, or metabolize cholesterol level, can vary from one person to the next. Now many of these differences can be measured by simple genetic tests, and the results can be turned into personalized diet and nutrition recommendations.


This new science, called nutrigenetics, studies how genes and diet interact. The key word here is "interact." As Rosalynn Gill-Garrison of Sciona, a company that develops genetic tests, points out: "Genes don't determine your fate." Rather these tests give you the information to make optimal choices for your health.1 A genetic test for bone health, for example, might indicate that you should consume more calcium and vitamin D, rather than saying that your bones are doomed to dissolve.

Currently several companies are developing consumer-friendly tests for known gene-diet interactions. You can be tested for genetic variations that affect bone health, B-vitamin metabolism, inflammation status, and utilization of certain antioxidants. The tests are typically done on a swab taken from inside your cheek. The sample is sent to a specialized lab, which analyzes DNA from the cells on the swab. You receive a report on which gene variations you have. A qualified health professional can explain the test results, and make specific diet and supplement recommendations to optimize your health.

What about genetic testing for weight loss?

The $64,000 question is this: When will a genetic test help me to lose weight? Unfortunately, this test does not yet exist. In fact, it is unlikely that just one test will ever answer that question. Registered dietitians Ruth DeBusk and Yael Joffe, co-authors of "It's Not Just Your Genes," write that genes may someday tell us which weight-loss diet is best, why one person burns more calories than another, and (even better) how to use gene technology to promote weight loss. 2 But they caution that hundreds of genes could impact weight. Deciding which of those hundreds are worth studying will be a daunting task.

The future of personalized diets

Diet and nutrition advice in the future will be increasingly personalized. As genetic researchers identify more gene-diet interactions, dozens of personalized recommendations for diet will be possible. Hopefully, before too long, weight control will also be part of that mix of genetic tests. In the meantime, the first generation of nutrigenetic tests is available for several important diet-gene interactions. One-size-fits-all diet advice will be a thing of the past.

1 Personal communication 7-10-07.

2 DeBusk and Joffe, It's Not Just Your Genes. BKDR Publishing c.2006: pp108-115.