You’ve probably heard of 23andMe. Until recently, they provided direct-to-consumer genetic testing. However, at the moment, they are no longer providing health-related genetic reports (here is a NEJM article on the controversy surrounding 23andMe’s genetic testing services). Instead, they are now offering ancestry-related genetic reports and uninterpreted raw genetic data. [Update on 23andMe]
Genetics, specifically the field of personalized genetics/genomics, is still quite young. We still don’t really know what our genetic information can tell us about our current and future health. We have figured out the easy stuff- single gene mutations that lead to diseases like Huntington’s and cystic fibrosis. But we don’t really know yet what genes or mutations are responsible for more common conditions like heart disease and Alzheimer’s, as they are unlikely to be caused by any one gene- it is most likely a complex interplay between many genes and the environment. 23andMe used single nucleotide polymorphisms (SNPs) as markers for disease. A SNP is a single nucleotide substitution in the human genome that occurs in more than 1% of the population. Many genome-wide association studies (GWAS) have tried to find associations between SNPs and disease.
Despite the difficulties 23andMe has been having with the FDA, it looks like biotech companies are still looking to try their luck at direct-to-consumer genetic testing. Today at work we found the following package from Inherent Health: “Your Personal Weight Management Genetic Test“.
Given how little we understand about our genome, I wondered exactly how this company was going to use our genetic data to help us manage our weight. On the back, I found a sticker with a description.
“This test is based on a study, funded in part by Inherent Health, in which 240 overweight pre-menopausal women followed either a very-low carbohydrate diet, a low-carbohydrate diet, a low-fat high carbohydrate diet, or a very high-carbohydrate diet for one year. Study participants were provided instructions by a registered dietician for 2 months concerning how to follow their assigned diets; some instructions included behavioral modification techniques. Participants’ DNA were analyzed and the study concluded that after 12 months participants who possessed specific gene markers lost, on average, more weight following one type of diet than another. Due to the emerging nature of this area of science, the understanding of the strength of the relationship between genes and diet is evolving.”
I thought the whole idea was pretty funny. A genetic test to tell you how well you will respond to certain diets? Given that the study only enrolled women, I’m not sure how useful these results would be for men. Also, when it comes to diet, there are so many variables to take into a consideration. Did all the women stick to their diets? What exactly did they eat? Is it more about willpower (is that genetic?) or genes/metabolism? Is your metabolism only determined by your genes? What other environmental variables could be playing a role? (Here’s an article saying that people don’t accurately report what they eat in studies).
I’m pretty sure there will be some false associations between genes and diet response just because of the numbers of variables that can affect response to a diet. If someone asked me to interpret their test results, what I would tell them probably would be the same no matter their results: “Limit portion sizes, cut out junk food, cut out sweet drinks, cut out fake sugars and fake anything, cut down on carbs, eat fruit, veggies, and some fat.” I’d like to see the results of that study… how well exactly did the women do on the various diets?