Should you let your genes decide what you eat? The field of nutrigenomics certainly leans in that direction. Frustratingly, there are two sides to nutrigenomics. On the one hand, it is a research endeavour trying to shed light on the interactions between the food we eat and the molecules in our body. On the other hand, it is a commercial endeavour piggybacking on the public’s fascination with DNA and the personalization of care.
Is it worth the hype?
Everything everywhere all at once
Genes can influence how we process food. You may have seen food labels stating that the product “contains phenylalanine.” Phenylalanine is one of the many building blocks of proteins, but people with a disease called PKU (phenylketonuria) have a mutation in a gene that results in an ineffective enzyme. They can’t process the phenylalanine they get from food. It accumulates and can lead to irreversible intellectual disability. To avoid this, they must adhere to a special diet that restricts their intake of phenylalanine, hence the food label warnings.
PKU, lactose intolerance, and the alcohol flush reaction—in which mutations in a gene impair the processing of alcohol, leading to skin flushing and rapid intoxication—all remind us that specific mutations can impact how we process food. But nutrigenomics is not interested in one or two mutations. It’s interested in all of them.
Nutrigenomics is part of a movement in molecular biology toward big data. Genomics looks at the genome, meaning all of our genes. Transcriptomics looks at the transcriptome, meaning all of the RNA molecules that serve as intermediaries between our genes and the proteins they make. Likewise, we have a proteome, a metabolome, a microbiome, and an epigenome, and all of these holistic sets of molecules are studied by their corresponding “-omics.” Nutrigenomics wonders how our diet influences all of our genes, and their transcripts, and their resulting proteins, and how the carefully choreographed dance between all of these molecules is changed by the food we eat and the beverages we drink. It is akin to studying the impact of modern aviation on every single animal and plant on Earth.
It is, you’ll agree, a tall order.
If you have heard of nutrigenomics, either through an exalting media article or an ad for a test kit, you will be familiar with its promises. Dietary recommendations are usually one-size-fits-all, but what if your dietary advice was tailored to how your body works at the molecular level? If we tested everyone’s DNA in order to issue personalized dietary recommendations, we could prevent chronic disease and reduce healthcare costs, we are told. One review of the literature on the subject goes so far as to say that nutrigenomics might prove to be the panacea of the future.
This optimistic literature is often littered with Hippocratic ventriloquy. As an appeal to authority, articles often begin or end with quotes misattributed to the father of medicine, Hippocrates. At this point, Hippocratic quotes belong in everyone’s baloney detection kit. If you see one on a health website, run.
The research arm of nutrigenomics is certainly noble. Figuring out how specific foods influence the molecular symphony inside our body could lead to interventions down the road. But these interventions are being prematurely rolled out because, as it turns out, there is a lot of money to be made in nutrigenomics.
There are kits to be sold which, much like 23andMe’s direct-to-consumer genetic tests, trade your saliva sample and payment for personalized recommendations of what to eat and what to avoid. Besides test kits, the door is wide open to the future development of food products targeting people with specific mutations. A nutrigenomics company could not only sell you the test, but also the corresponding meal kits. Imagine getting tested for coeliac disease at your doctor’s office and, when your test comes back positive, your doctor also hooks you up with a regular supply of gluten-free food. That is what people in the nutrigenomics space are spotting in the distance.
While parsing the literature, I was surprised to see so many academics spinning off their early findings into a company that could sell services to customers, either directly or through some kind of health professional. The publicity is easy to get. Many of these companies offer a free test to a journalist, who then writes a puff piece about how amazing the process was and the ways in which they have tweaked their diet based on the company’s recommendations. Good luck finding the one-year follow-up article in which the journalist reveals if their new diet survived the test of time.
And these nutrigenomics companies all but say their tests will help prevent and treat medical conditions, like obesity and chronic diseases. It is, after all, one of the pillars of nutrigenomics: to translate the food-gene interactions into interventions that will reduce disease burden. But their websites often bury a hard-to-read disclaimer at the bottom, stating that none of this is intended to diagnose, treat, cure, or prevent disease. Is this honest? An even bolder disclaimer I saw reads, “Neither the company nor its affiliates warrant that the information on this site is accurate, reliable, or current.” Underneath the shouts that nutrigenomics will help curb chronic disease is a whisper that states that, like consulting a psychic, this is, legally speaking, for entertainment purposes only.
Behavioural issues
The kind of personalization that nutrigenomics offers at the moment includes, for example, the claim that a certain mutation leads to the slower metabolism of caffeine and a higher risk of heart attacks when regularly consuming the stimulant. Another mutation decides if you will lose fat on a high-protein diet or not. Also of interest is how genes affect the processing of vitamins and minerals in the body, and how these variations should impact recommendations for daily consumption.
But when the U.S. Government Accounting Office surreptitiously tested four nutrigenomics companies in the mid-2000s, i.e. the early days of nutrigenomics services, it found that these companies had essentially violated their disclaimer against diagnosing medical conditions, predicting instead the development of serious diseases like cancer and diabetes. And those predictions, health experts agreed, could not actually be made based on the genetic information analyzed. Around the same time, a review of the gene-diet associations tested for by seven different companies concluded that there was insufficient evidence for them. The landscape does not appear to have significantly changed since then.
There is a larger issue with the current application of nutrigenomics and that is the size of the impact it can have on our health. The gene-diet links tested for by nutrigenomics kits currently are unlikely to have a major effect on someone’s overall health. Meanwhile, only 3 out of ten Canadians eat enough fruits and vegetables every day. (For Americans, that number is 1 out of ten.) Half of Canadian adults meet physical activity recommendations. Between 1 in 3 and 1 in 4 Canadian adults is not getting enough sleep. And 1 in ten Canadians smokes. Improving these statistics does not require scrutinizing someone’s genes, but rather embracing well-known and universal health recommendations.
And this is where the real obstacle lies, both for public health recommendations and for personalized nutrition: information rarely changes behaviour. During a 2017 workshop on nutrigenomics held by the U.S. National Academies, a researcher who spun off his own academic work into a company that, at the time, had raised $54 million claimed that nutrigenomics was “really about empowering [his participants] with data.” But what do we do with the data? For most of us, food is not just fuel; it’s a social activity. We know that people choose what to eat based on convenience, appearance, price, taste, and social engagement, with health considerations further down the queue. During the workshop, a professor of nutritional sciences admitted that even experts are not robots. When dining with fellow nutritionists, she said, she would hear them say, almost with a guilty chuckle, “Well, I know I shouldn’t eat this, but I really like the way it tastes.”
Changing our behaviour is hard, even when we know what we have to do. When dieting, people tend to lose up to 10% of their weight in the first six months, but between a third and two-thirds of dieters regain more weight in the following years. And while people with an interest in promoting the value of nutrigenomics will argue that giving customers genetic information makes a difference, a 2016 systematic review and meta-analysis of the potentially biased data we have so far is grim. Genetic information is simply not a good motivator. Part of the reason may be that only 12% of American adults have the skills to understand much health information.
The “me” generation
The commercialization of nutrigenomics feeds into an increasingly myopic and egocentric view of health—that public considerations have been replaced by personal choices leading to personal rewards—and this kind of perspective, as it does in wellness, can backfire when the results don’t match the promises. It can also act as a distraction from larger issues. There are real problems with food security and socioeconomic disparities that play an important role in influencing people’s health. Solving these problems requires a public health perspective, not a focus on how one person’s genetic makeup might slightly increase their risk of a heart attack if they regularly drink coffee.
I did not attend that 2017 nutrigenomics workshop, which featured many higher-ups from companies like Nestlé, Coca-Cola, and General Mills, presumably as these companies stood to benefit from the development of food products tailored to people’s genetics. But reading its 154-page summary, it sounds like it may have been a bit shambolic. One of the speakers gave a talk on the genetics of the mitochondrion, that powerful energy factory present in our cells. His presentation concluded with the rather odd claim that Eastern medicine, which focuses on the unscientific notion of a life force often called qi, was probably effective by working through the mitochondrion.
Buried at the end of the report on this peculiar workshop, though, is an amazingly lucid and socially aware quote from an epidemiologist, Professor Cecile Janssens.
She said, “I’m sure that when I walk out of the building here later, and I see the people on the street, that I’ll question myself, ‘What have I been doing this entire day? Why have I not tried to solve a bigger problem for them, instead of trying to find a little benefit in nutrigenomics?’”
Take-home message:
- Nutrigenomics is both an active field of research and a commercial service that is interested in looking at the way in which our diet influences the molecules in our body, like DNA, RNA, and proteins.
- Tests conducted in the mid-2000s and a review of the evidence then showed that the promises made by commercial nutrigenomics services were not supported by good science.
- There are more effective and universal recommendations if we want to improve population health, including eating more fruits and vegetables, exercising more, and getting enough sleep.
