Why do certain diets work for some people and not others? What made Julia Child want to throw her cilantro on the floor? We all have our individual food preferences, but what if you could optimize your diet based on your genes? Although genomics (the umbrella term for the interaction between genes and the environment) is an established field, nutritional genomics is relatively new. Essentially, it’s the study of the interaction between an organism’s genes and the bioactive components of the food that it eats. Identifying gene variants that respond differently to food provides the basis for tailored nutrigenetic diets, which have the potential to help people achieve desired health outcomes such as weight loss or reduced risk of chronic disease.
Researchers are still investigating the different ways in which genes and nutrients interact. A single base pair variation in a gene, called a single nucleotide polymorphism (SNP), may change the way that an individual reacts to some foods. Nutrients may also influence genes at the molecular level by affecting processes such as transcription (the conversion of DNA to RNA, which is important for gene activity) and protein expression patterns. Genotypic variation may change individual requirements for certain nutrients such as vitamin C and folate, a B vitamin known largely for its importance in preventing neural tube defects. These genetic differences may also affect an individual’s risk for adverse health events such as heart attacks and strokes. For example, researchers have identified several key genes with polymorphisms that affect levels of cholesterol and triglycerides in the blood.
Consumer interest in personalized nutrition is high and for-profit enterprises have been quick to take advantage of this trend. However, consumers need to be careful. Companies that offer direct-to-consumer genetic testing may fudge the distinction between correlation and causation for marketing purposes; just because a certain genotype is associated with a particular health outcome does not necessarily make it responsible.
Genetic factors are known to contribute significantly to obesity risk, so many researchers are focused on figuring out how to personalize nutrition to make weight management easier. There are many companies that currently offer genetic tests that identify obesity-related polymorphisms. Despite the exciting potential, tests like these can be misleading or inconclusive. Pinpointing one specific gene that’s responsible for weight gain is difficult, partly because of the the interactions between genes at specific loci. The extensive number of variables involved in weight regulation (built environment, food availability, socioeconomic status, etc.) also complicate the puzzle.
If used correctly and based on solid scientific research, nutrigenetic diets have the potential to improve health outcomes for individuals by capitalizing on genetic differences. The body of evidence supporting their efficacy is small right now, but advancements are being made in science and technology that could improve the utility of genetic testing for personalized nutrition in the near future. As researchers continue to explore this field, it will be critical for popular press outlets, consumers, and companies that offer direct-to-consumer genetic testing to clearly distinguish between correlation and causation and think critically in order to promote the most ethical and effective personalized nutrition.
References
Cahill, Leah E., Bénédicte Fontaine-Bisson, and Ahmed El-Sohemy. “Functional genetic variants of glutathione S-transferase protect against serum ascorbic acid deficiency.” The American Journal of Clinical Nutrition 90.5 (2009): 1411-1417.
Crider, Krista S., et al. “MTHFR 677C→ T genotype is associated with folate and homocysteine concentrations in a large, population-based, double-blind trial of folic acid supplementation.” The American Journal of Clinical Nutrition 93.6 (2011): 1365-1372.
Cornelis, Marilyn C., et al. “Coffee, CYP1A2 genotype, and risk of myocardial infarction.” The Journal of the American Medical Association 295.10 (2006): 1135-1141.
Frankwich, Karen A., et al. “Differences in weight loss between persons on standard balanced vs nutrigenetic diets in a randomized controlled trial.” Clinical Gastroenterology and Hepatology 13.9 (2015): 1625-1632.
García-Cañas, Virginia, et al. “Advances in Nutrigenomics research: novel and future analytical approaches to investigate the biological activity of natural compounds and food functions.” Journal of Pharmaceutical and Biomedical Analysis 51.2 (2010): 290-304.
Speliotes, Elizabeth K., et al. “Association analyses of 249,796 individuals reveal 18 new loci associated with body mass index.” Nature Genetics 42.11 (2010): 937-948.
Subbiah, MT Ravi. “Nutrigenetics and nutraceuticals: the next wave riding on personalized medicine.” Translational Research 149.2 (2007): 55-61.
Concise, thank you for sharing.
Hopefully the work that Karen Frankwich started will continue. With positive results it might be possible to proceed to larger population trials.
It is logical that the efforts in sustaining a healthy weight may be more likely to succeed if the overall dietary needs are met consistently and constantly. Individuality seems to preclude the “one-size-fits-all” diet…
Perhaps the aversion to, and cravings for, certain foods are genetically linked with geographic location, as well? After discovering my own disinclination of that particular green herb, I read some of the results from the Monell Center and work done by Dr. Wysocki, implying that association.
I look forward to learning more.