What Does Personalized Nutrition Actually Deliver?

There’s a lot of focus on personalized nutrition, but maybe we should focus on taking personal responsibility for our health.

“Personalized nutrition (PN) is rooted in the concept that one size does not fit all,” and who doesn’t want to think they’re special? The idea of personalized nutrition is inherently appealing to our ego; that’s why simple messages recognizing individuality deeply resonate with us and why such messages are popular in marketing and sales. This focus on uniqueness has spurred the creation of personalized foods, along with the suggestion that “3D Food Printing seems to be a good candidate for food customization.”

Now, there certainly are some legitimate differences between people. Some have a peanut allergy and keel over if they eat a peanut, others have celiac disease and need to avoid gluten, and some are genetically lactose-intolerant. There’s an enzyme mutation common in some parts of Asia that protects against alcoholism because people with the altered enzyme don’t metabolize alcohol as efficiently, so toxic metabolites build up. I published a fascinating video about fast versus slow caffeine metabolizers and the difference in health benefits that actually extends to athletic performance. Caffeine is ergogenic—performance-enhancing—but only in fast metabolizers, shaving more than a minute off 10 kilometers (about 6 miles) of cycling, whereas slower metabolizers either got no benefit or the caffeine actually slowed them down, adding two minutes to their cycling time, depending on which kinds of genes they have that code the enzyme that breaks it down. You can see these results below and at 1:24 in my video How Useful Is Personalized Nutrition?.

But for most people, in most situations, we are more similar than different.

While there is a specific minority of people who need a more personalized approach to nutrition, there is currently insufficient evidence to support truly personalized nutrition for most people. Yet a surprising number of direct-to-consumer genetic testing companies have proliferated, offering personalized nutrition advice. For example, there are supplement-hawking companies that claim to help consumers optimize micronutrient status based on a handful of genetic variants, even though most variants explain just a few percent of the difference in levels between people.

Personalized nutrition is part of a broader push towards personalized medicine, also known as precision medicine. There is a “massive cultural allure” of personal control over diagnosis, treatment of disease, and prevention, spurring demand and intense commercialization. But unlike monogenetic diseases—which are rare genetic diseases caused by a single malfunctioning gene, like hemophilia or sickle cell anemia—most diseases are caused by a complex interaction between multiple genes and environmental factors, which pose a “major challenge for the realization of personalized medicine.”

Take something like adult stature, for example. Researchers have found at least 40 locations on our chromosomes that have been associated with human height, which is strongly inherited. The genes from parents account for about 80% of the difference in height between people, yet those dozens of identified genes explain only about 5% of height variation between individuals.

Researchers find those genetic links by using genome-wide association studies, in which all the chromosomes are scanned to look for statistical associations between diseases and any particular stretches of DNA. That’s interesting, but companies marketing genetic susceptibility tests are reinterpreting these data as if they predict individual risks. But all you’re really getting are modest genetic associations with a slight increase in disease risk and with little predictive power when compared to more significant contributions of things we already know, like lifestyle behaviors. Currently, the practice of using a person’s DNA to predict disease “has been judged to provide little to no useful information.”

For example, let’s say a person’s genetic analysis says they’re at slightly greater risk for some grave condition compared to others in their ancestral group. This person was advised to exercise, keep their weight down, not drink too much alcohol, and eat fruits, vegetables, and whole grains. It’s sound advice, but we should be living this way regardless of our genetic risk. And we know—at least we should know—these simple, basic strategies to reduce risks of common chronic diseases. “The problem, of course, is that very few individuals live this way. Actually, to be more precise, almost nobody lives this way.” That’s not just hyperbole—nationwide surveys show that nearly everyone in the United States consumes a diet that’s not on par with even the wimpy recommendations of the Dietary Guidelines.

Indeed, almost “no one in the United States is eating a healthy diet.” Findings like that remind us that when it comes to public health, “worrying about personalizing our preventive strategies based on genetic risk information borders on the absurd.”

Doctor’s Note

Here’s the video I mentioned about fast versus slow caffeine metabolizers and the difference in health benefits extending to athletic performance: Friday Favorites: Do the Health Benefits of Coffee Apply to Everyone?.

For more about lifestyle approaches, check out related posts below.