Ads for DNA-based meal and supplement plans are all over the place. They sound like cutting-edge science. But will eating or taking vitamins according to your genes really make you healthier…or help you avoid diseases? It depends on the kind of DNA test—and how you apply the results.

Generally, popular DNA-based meal or supplement companies such as Fitgenetix and The DNA Diet Plan use either their own gene test or results from a gene-testing company such as 23andMe to compile a “nutritional report.” The report might indicate, for instance, a biomarker showing deficiency in vitamin D or omega 3s. The company then offers meal plans—or even delivered meals—centered on foods that replace the “missing” nutrients. Or, if you’re trying to lose weight, you can choose a meal plan that provides carbs, protein and fat in amounts and proportions tailored to your personal DNA needs to make it easier, at least in theory, to shed the pounds.

Sound too good to be true? It is. Aside from the cost, the “science” is flawed.

GENETIC VS. GENOMIC TESTING

The genetic testing these companies typically use looks only at single genes and mutations that are passed from parent to child. Such tests are good at identifying genetic variants involved in diseases such as sickle cell anemia or the BRCA gene that increases risk for breast and other cancers.

Single genes and their mutations can alert only to a predisposition for a health condition or disease—they can’t predict that you’ll get it. They also don’t take into account lifestyle and environment. For instance, a predisposition for heart disease doesn’t guarantee that you’ll have a heart attack. But living mostly on fast-food will make that outcome more likely than following a Mediterranean-style diet. Sometimes, though, a genetic mutation is what it is—neither diet nor lifestyle can change it…nor affect the outcome.

That said, knowing your genetic profile can help guide toward healthier food (and lifestyle) choices—if the test you get is a genomic test. Rather than looking at genes and gene variants singly, genomic testing looks at multiple genes within a system and how they work together. The impact of individual genes may be minimal. But the impact of multiple gene variants within a biochemical pathway can be much greater. The number and combination of such gene variants that you have can give a better picture of actual risk…and also help identify supplements and nutrients that might mitigate the risk.

Example: There isn’t a single gene for osteoporosis. However, there are dozens of genes that affect bone health and bone formation. Take the way cells absorb vitamin D, for instance. There is a gene that helps the body convert sunlight to vitamin D…genes that control how the vitamin is transported to the kidneys and liver where it gets further activated…and cells that allow receptors in those organs to admit the vitamin into the cells. If you have gene variants anywhere along that pathway, your body may have difficulty getting enough vitamin D from food, sunlight or even typical supplement dosages. To keep vitamin D at a healthy level in your body, you may need to flood your cells with a higher dose.

Genomic testing can also shed light on ways to tweak meals and snacking habits to make them healthier.

Example: Gene variants that affect leptin (the hormone produced by fat cells that suppresses appetite and regulates fat storage) and ghrelin (the hormone that increases appetite) can interfere with the body’s hunger/satiety signals. So, you’ll still feel hungry even after you’ve consumed sufficient calories. Knowing that your “hunger” is driven by your genes, not a need for more fuel, can help you figure out what behavioral changes you need to make—such as counting calories, measuring portions, limiting yourself to one serving and/or eating a diet higher in protein and whole grains to help suppress ghrelin.

Genomic testing also can point out a genetic intolerance for carbs so you’ll know to eat fewer of them…or a genetic difficulty absorbing plant omega-3s so you know to be sure to include more fish in your diet…or a predisposition to inflammation so you can focus on anti-inflammatory foods.

PUTTING YOUR DNA TO THE TEST

Knowledge is power, but it doesn’t come cheap. If you want to try genomic testing, prepare to shell out at least $1,000. Because there are many companies offering different versions of this kind of DNA testing, you’ll also need to do some research.

Ask questions. Check which genes the company tests for. Good companies look only for genetic variants that affect diet and lifestyle—and provide supporting research. Bear in mind that our bodies are constantly responding to internal and external factors, so don’t expect your genomic test results to help you achieve dietary perfection. Instead, use the results to make adjustments to accommodate your genetic challenges. That could mean eating more vegan meals to safeguard your cardiovascular system…or sticking to exercises that won’t exacerbate a risk for tendon and ligament injuries.

Choose a company that works with a health professional. Most reputable labs work only through a health professional, such as a registered dietitian, naturopathic doctoror an MD who is also a trained genomics expert. These experts can interpret the results in the context of your medical history (and your family’s), any pertinent lab work and your daily habits, and then make recommendations based on the combined information.

If the company you’re thinking of using does not have their own health professional, ask if they can recommend one who is knowledgeable in genomics near you, or one who will work with you remotely. If neither choice is an option, you can take the results to an integrated, functional medicine practitioner or naturopathic medical doctor. While he/she may not be expert in genomics and will not be able to take into account specific genomic information, such practitioners are trained to treat the whole person—taking into account physical, psychological and environmental factors.

However, the bottom line is that you don’t need a DNA test to reduce your chances of developing chronic diseases and add years to your life. Just eat more fruit, vegetables and nuts…eat less meat and overly processed food…and improve your sleep. This old tried-and-true advice may not be sexy. But it works.