When I google “DNA diet,” the first thing I see are four ads for various companies making vague claims about using genetic test results to create individualized food recommendations. These businesses are part of the growing personalized nutrition (or “precision nutrition”) trend, in which consumers are being sold wellness plans and/or products based on their unique health information—everything from lifestyle habits and gut bacteria to, yep, DNA. Frankly, the idea of receiving dietary advice based on your genes is compelling. More and more people are getting hip to the idea that generic diet plans nearly always fail when it comes to weight loss, and that there’s no single way of eating that guarantees health. Still, many folks hope that their “perfect” diet is out there somewhere.
Jennifer Williams, 42, for one, did genetic testing through 23andMe in 2017. “I nerded out on my results when I got them,” she tells SELF. And when she realized that she could send her results to a wellness company for personalized diet and exercise recommendations, she was intrigued.
Williams says she “technically” fits the medical definition of a person with obesity, but she has worked hard “to not give a shit about that”—especially because research shows BMI is a less-than-perfect measure of overall health. And even though weight isn’t necessarily a determinant of heart health in particular, Williams was worried she could face “a big cardiovascular-health downturn” similar to what her mother experienced. “I thought digging into diet (and to a lesser extent fitness—I know what I like to do exercise-wise) could be interesting,” she says.
But when Williams’s diet and exercise recommendations arrived, she was underwhelmed. Even though they were “personalized” based on her DNA, they seemed vague and not very actionable. For example, the assessment indicated a “high sensitivity” to carbohydrates. “The genes in this panel impact the way you metabolize and assimilate refined carbohydrates, and the combined effect of your variants puts you with a slightly increased effect, meaning you are less well placed to deal with excess carbohydrate intake than most,” her report read.
There were other similarly general results—low saturated fat sensitivity, raised omega-3 need, normal vitamin B and folate needs, raised salt sensitivity, and more—that came with equally abstract explanations like, “You are better placed than most to deal with fat intake, genetically speaking.” Then there were pieces of advice that lined up with the same general recommendations we hear all the time: “It is recommended that you consume adequate amounts of antioxidants,” and, “It is recommended that you include omega-3 fatty acids in your daily diet.”
According to researchers, there’s a reason why the “personalized” DNA diet plans touted by these wellness companies are filled with generalized scientific jargon and loose recommendations that come with no promises: There’s just not enough evidence yet for truly personalized gene-based diet plans.
What does DNA have to do with nutrition?
“Trying to understand how what we eat affects our genes is super complicated,” Monica Dus, PhD, assistant professor of molecular, cellular, and developmental biology at the University of Michigan, tells SELF. “For one, everything we eat is this extremely complex mixture of things.” There are many different nutrients—carbs, fat, protein, vitamins, and minerals—in every food, plus other non-nutritive substances like chemical residues, coloring agents, and additional substances we may not even know about, says Dr. Dus.