Genome-Tailored Diets May Be Premature

Individual genomic profiles promise the ultimate in personalized medical care – which includes dietary guidance. In fact, as popular news sources have reported, personalized nutrition testing and services are already trying to read genomes as if they were menus. But it may be too early to book a reservation at Chez Genome. According to scientists based at the Technical University of Munich (TUM), the genetic factors commonly cited in nutrition studies are not consistently correlated with the consumption of total calories, carbohydrates, and fat.

The TUM team systematically reviewed gene-diet interactions that have been described in the scientific literature. Articles that were published between 1994 and 2017 and that considered adult humans were included in the review.

Detailed findings appeared in the journal Advances in Nutrition, in an article titled, “Associations between Single Nucleotide Polymorphisms and Total Energy, Carbohydrate, and Fat Intakes: A Systematic Review.” According to this article, the TUM team built an initial database of more than 10,000 scientific articles. Of these, 39 articles were identified for a relationship between genetic factors and total energy, carbohydrate, or fat consumption.

“The fat mass and obesity (FTO)-associated gene, as well as the melanocortin 4 receptor (MC4R) locus, were most frequently studied,” the article indicated. “Limited significant evidence of an association between the FTO SNP rs9939609 and lower total energy intake and between the MC4R SNP rs17782313 and higher total energy intake was reported.”

“In all studies, we most frequently encountered the FTO-associated gene as well as the melanocortin 4 receptor gene (MC4R),” emphasizes Christina Holzapfel, Ph.D., a researcher at the Institute of Nutritional Medicine at TUM. “There is only limited evidence for the relationship between the FTO gene and low energy intake as well as between the MC4R gene and increased energy intake.”

The TUM team argues that to date there exist no indications that certain genetic factors are associated with the total intake of calories, carbohydrates, and fat. The current state of knowledge, the team adds, is still too limited for deriving individual nutritional recommendations based on genetic information, including recommendations for weight management.

To date, around a hundred genes have been identified which are related to the body mass index (BMI). However, the functioning of these genes, as well as the biological mechanisms behind them, are still largely unknown. The investigation of the relationship between genetic factors and nutrition can shed light on whether the genes which are linked to BMI play a role in nutrition.

“Several commercially available genetic tests (direct-to-consumer tests) are currently offered with the promise to provide reliable information for better prevention or treatment of obesity and related metabolic disturbances,” the current article noted. “However, a strong evidence base for these tests is currently lacking.”

“Human studies with detailed phenotyping, such as studies based on a genetic pre-analysis of the participants, are necessary in order to determine the interactions between genetic factors and diet on body weight,” the TUM team indicated. “The ‘Personalized Nutrition & eHealth’ Junior Research Group funded by the Federal Ministry of Education and Research, which is part of the enable nutrition cluster, is working precisely on this.”