Ask Keri: Genetic testing services that tell you what to eat based on your DNA are everywhere. Will tailoring my diet to my genes lead to better health?
Keri Says: Scientists have quickly been unraveling the complex ways that genes impact overall health over the past few decades, especially since the completion of the Human Genome Project in 2004. As more information becomes available, more companies spring up to sell you on how knowing more about your unique genetic code can help you optimize your health—which diseases you’re more at risk for, which workouts are best for your body, and yes, DNA-based diets.
You’ve probably seen some of the biggest names in the space, like Habit, uBiome, Nutrigenomix, DNAFit, and FitnessGenes, all of which deliver personalized recommendations about what you should eat (and in some cases, how you should exercise) based on some version of a DNA test.
Overall, my take is that while some of these tests may provide a genuinely helpful tidbit here or there, they are generally based on science that is not nearly established enough to rely on. Right now, there is no solid evidence that eating a certain diet based on your specific genes will make you slimmer, happier, or healthier. (Sorry!) There’s plenty of evidence eating more vegetables will. So, unfortunately, it pays to focus on the less sexy factors (as usual, right?).
Here are some details on how I’ve come to these conclusions.
Research on DNA-Based Diets
Nutrigenomics is the study of how genes and nutrients interact, and guess what? We do know for sure that they do a lot of interacting. Specific foods and nutrients alter gene expression in major, complex ways, which in turn impact metabolic processes, and therefore, your overall wellbeing.
The relationship in the other direction is just as complicated and even less understood. Advocates of DNA-based diets point to some evidence that suggests people metabolize carbs, protein, and fats differently based on their genetic makeup, but there is no research that shows tailoring your diet to that information will change your life. In other words, there haven’t been clinical trials to show these kinds of diets work, and a 2015 meta-analysis found the evidence is seriously scant. “As solid scientific evidence is currently lacking, commercially available nutrigenomics tests cannot be presently recommended,” the authors concluded.
Reporters have also shown that results from tests on the market sometimes even contradict each other on the exact same genes.
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The Bottom Line
In a deep-dive look at this topic on Wired, one researcher offered the journalist a metaphor that I think is super helpful when it comes to understanding why even when we know a gene may do one thing related to nutrition, in most cases we don’t know what impact (if any) making a habit switch based on that tiny piece of info will have.
“Alun Williams, a reader in sport and exercise genomics at Manchester Metropolitan University, told me that tying traits to DNA is like absorbing a book by reading only one word per page—you have information, but at the end you have no idea what the book was actually about. Throughout a person’s life, environmental forces, such as how frequently you exercise or what you eat are constantly changing your genome. In short, fitness, like other complex traits including height and alcoholism, doesn’t come down to just a handful of genes—there could be hundreds or thousands that play a part.”
The few cases where there are exceptions? Knowing you have a genetic variant for Celiac disease, for sure, or a gene that affects how you metabolize caffeine, which could help you manage heart disease risk factors.
One last fun fact: In an NBC article, the founder of Nutrigenomix said “There’s research now showing that people who get DNA-based dietary advice are more likely to follow recommendations.” So if it works, it could be because subconsciously you take the recommendations—which in many cases would be the same kind of advice you’d get from any nutritionist—more seriously simply because someone told you it was made.for.your.body. You’re no chump, and these tests are not cheap.
Am I saying someday we won’t all be eating a diet perfectly tailored to our unique genetic profile? Nope, totally could happen! For now, remember what I said about vegetables? Yeah, boring, I know. Now go pile them on your plate.
(Featured Photo: Eszter Biró via Stocksnap.io)