Should your DNA determine what you eat?

January 7, 2019

The physiological effects of some of what we consume, from lactose to caffeine, differ greatly from person to person. Yet, food guides and nutritional data are often all-encompassing. Is this the most effective way for us to determine what makes it to the plate?

Ahmed El-Sohemy, a professor in the nutritional sciences department at the University of Toronto, argues that there’s a better way.

“Current recommendations are that everyone can drink up to four cups of coffee a day. Well, for half of the population who are slow metabolizers, any more than two cups a day will actually be harmful,” he explained.

“We need to segment the population based on their genetics for giving recommendations. With coffee and caffeine that’s just one example, but we can apply that to virtually every dietary factor.”

El-Sohemy is the founder of Nutrigenomix, a company that offers tailored, personalized nutritional advice to clients based on a sample of their DNA.

This emerging strain of science, called nutrigenomics, studies the connection between one’s genetics and how their body responds to certain drinks, foods and supplements.

Scientists can determine a person’s genomic information in a few ways, from samples of saliva to blood and hair.

A different method that researchers are looking into is studying one’s gut microbiomes, made up of bacteria that lives in the small and large intestines.

“We’re looking at the gut bacteria to see how that influences a person’s response to diet. But the field of microbiome research is really, I’d say, 10 to 20 years behind the field of human genetics and response to nutrition,” El-Sohemy said.

“Some individuals might have bacteria that break down carbohydrate quickly and others may not. And that might influence how our blood glucose might respond to a carbohydrate meal or something, but it’s very early on in these studies,” Dylan Mackay, a nutritional biochemist with the University of Manitoba, explained.

“I don’t think there’s enough there to start recommending diets based on them.”

Another limitation with studying gut microbiomes is the rapid rate at which a person’s gut bacteria can change. What someone eats can completely alter the bacteria for days to come, which makes it difficult to give reliable nutritional recommendations based solely on the bacteria, El-Sohemy explained.

It’s not just microbiome-based food advice that worries Mackay. It’s the discipline as a whole.

“The evidence that the current tests are based on is simply quite poor, in my opinion. You’ll notice that all these tests for dietary recommendations are never regulated by the FDA or Health Canada as diagnostic tests,” he said.

“I just think we need to make better evidence before we can make recommendations.”

Mackay stressed the difference between an individual gene and a whole genome sequence; the latter is an organism’s entire chromosomal DNA makeup. Nutrigenomics, he explained, focuses only on the individual gene.

“Most of the genetic variations that we look at in nutrigenetics are very, very minor influences to the point where I think it might not even be worth it to look at. I mean other than for fun.”

El-Sohemy, however, argues that nutrigenomics provides something that other dietary advice does not.

“This kind of information is actually better than the current recommendations that we’re giving to everybody, of the one-size-fits-all model.”

Despite the skepticism of people like MacKay, nutrigenomics has infiltrated the world of personalized health in a big way.

According to a September, 2018, report from Market Research Future (MRFR), personalized nutrition offers manufacturers opportunities to develop relationships with consumers. This means a lot of big-name corporations are beginning to offer DNA-based diet advice, including Nestle, Danone, Carlyle Group, Amway and Abbott Laboratories.

And while the industry is continually expanding as people opt to individualize their approaches to personal health, Mackay hopes the research doesn’t end here.

“While I’m still skeptical overall in these dietary recommendations, I don’t think that the concept of it is totally unsalvageable. I think we need more research into it to determine the optimal ways to use this personalization.”