Nutrigenomics: Is It Ready for Prime Time?
Personalized nutrition therapy that takes into account one’s genotype has tremendous promise, but the evidence supporting its use in routine patient care is mixed.
By John Halamka, M.D., president, Mayo Clinic Platform, and Paul Cerrato, MA, senior research analyst and communications specialist, Mayo Clinic Platform
On the wish list of many clinicians and patients is a precise blueprint that tells individuals their predisposition to specific diseases, their unique biochemical profile, as well as their requirements for physical activity, nutrients, and much more. While we are a long way off from having such blueprints, we are slowly approaching this ideal personalized medicine scenario. Nutrigenomics is one such area that offers promise. But a closer look at the specialty demonstrates the need to separate the wheat from the chaff.
The journal Nature describes nutrigenomics as “the study of the effects of food and food constituents on gene expression, and how genetic variations affect the nutritional environment. It focuses on understanding the interaction between nutrients and other dietary bioactives with the genome at the molecular level, to understand how specific nutrients or dietary regimes may affect human health.” In the last few years, there has been important research on these issues, as well as the launch of several personalized nutrition services claiming they can pinpoint a person’s needs for various vitamins, minerals, and macronutrients like fat and protein. Some of the more sophisticated entrepreneurs provide brochures with numerous references to the scientific literature. When we examined the content of these references, we found a mixed bag of supporting evidence.
There is credible evidence to suggest that mutations in the fat mass and obesity-associated (FTO) gene may have an impact on a person’s calorie needs. The research suggests that single nucleotide polymorphisms (SNPs) in this gene influence an individual’s feeding behavior and their energy expenditure, i.e., the rate at which they burn calories. Several vendors that offer nutrigenomic services include FTO analysis as part of the testing panel. People who have inherited an uncommon FTO variant from both parents are often found to weigh about 3 kg more than individuals with a more common FTO variant. They also have a 70% greater risk of falling into the obese body mass index (BMI) range. However, a systematic review and meta-analysis of 8 randomized controlled trials found that patients’ responses to weight loss regimens were not significantly different regardless of which genetic variant they possessed. Put another way: “These findings show that individuals carrying the minor allele respond equally well to dietary, physical activity, or drug-based weight loss interventions and thus genetic predisposition to obesity associated with the FTO minor allele can be at least partly counteracted through such interventions.” On a more positive note, a Harvard-based prospective study found that patients with a certain FTO variant lost more weight on a high protein diet when compared to those on a low-protein regimen.
Unfortunately, many of the other references used to support commercially available nutrigenomic services are less credible. Many of the studies only establish a correlation or association between SNPs and a greater need for a specific nutrient; as most clinicians know, correlation rarely proves causation.
Even more telling are studies that compared personalized conventional nutritional counseling to personalized nutrition services that took into account phenotypic and genotypic characteristics. For example, The Food4Me Study, a randomized controlled trial, did just that, and found that the latter approach offered no advantage in changing patients’ eating habits.
To be fair to vendors and innovators in personalized nutrition, it’s important to point that the Food4Me Study was published in 2017, and a lot has happened in the field since then. With that in mind, it’s safe to say: Nutrigenomics may not be quite ready for prime time, but don’t turn off your TV. It’s on the way.