June 2, 2022 – Every so often, the conventional wisdom about healthy diets changes.

Sometimes the shift is seismic, like the low-fat craze that took hold in the 1990s. Other, more gradual changes have brought us to the current focus on the overall diet rather than any single nutrient. But what if the advice keeps changing because no one way of eating is right for everyone?

The latest research is moving the needle toward precision nutrition – highly customized diets based on your microbiome, DNA, or other things. Quite a few are already available, but the science may not match the marketing.

How Precision Nutrition Works

The concept seems straightforward, but it’s infinitely complicated. Since no two people are completely alike in their DNA – not even identical twins – each of our bodies will respond differently to foods and the bacteria that grow in our gut as we digest them. Precision nutrition (sometimes called “personalized nutrition”) uses artificial intelligence and data collected from other people to predict how your body will react to specific foods.

Advocates for precision nutrition are working on three key fronts:

  • Nutrigenetics looks at how genes influence the way your body uses the nutrients you eat. Which means even if you’re getting enough of a certain nutrient, your body may not be able to process it well.
  • Nutrigenomics essentially flips that around. It examines how the foods you eat can change how your genes are expressed. “Like for obesity, you may have a certain set of genes, but that doesn’t necessarily mean you’ll express them,” says James Marcum, PhD, of Baylor University, author of a review of literature on nutrigenetics and nutrigenomics. “But if you eat food that expresses those genes, it leads to obesity.”
  • Microbiome research focuses on how the microbes in your gut affect your health. Since everyone’s microbiome is different, the thinking goes, so is each person’s ideal diet.  Genes play a role here, too, because the makeup of your microbiome is influenced to some degree by your genes.

Today’s Personalized Diets

As many as 400 companies already offer some kind of personalized diet program. But not all have a solid scientific foundation. Diets based solely on your DNA, for instance, are not ready for prime time – your body’s response to food depends on much more than just genetics.

“Each one of us is so complex, we’ve just scratched the surface,” says Marcum. “There’s more we don’t know than we do at this stage of the game. We’re seeing that the more you appreciate how complex the system is, the more you realize it may be hard to predict how a person is going to respond.”

But with some of the programs already on the market, the research is promising. DayTwo specializes in metabolic health, aimed at people with diseases like diabetes and obesity. They analyze your microbiome and other health markers to provide a customized eating plan, and they’ve published research in peer-reviewed journals to back it up. Currently, DayTwo is only available through health plans and employers.

Another company, Zoe, intends to improve overall health or help with weight loss. For $294 plus a monthly membership fee, the company will create a custom plan based on your microbiome, blood sugar, and blood fat. Zoe’s offerings are based on the Personalized Responses to Dietary Composition Trial (Predict) Study, which is ongoing.

The Nutrition for Precision Health Project

The National Institutes of Health has begun a major research project focused on precision nutrition. Called Nutrition for Precision Health (NPH), the program is awarding $170 million over 5 years to fund studies at six centers across the country. Researchers are recruiting a diverse pool of 10,000 people to develop algorithms that can predict how your body responds to various parts of your diet. They’ll be looking at the diet, genetics, microbiome, physiology, and environment of the people in the study, along with other things.

“The evidence base is young,” says NPH coordinator Holly Nicastro, PhD. “We don't want to just look at the microbiome, we don't want to just look at genetics, because we need to be studying how all these things work together -- other systems in the body, psychosocial factors, demographic factors, and other things that haven't been traditionally captured in nutrition study.”

After the  5-year studies gather enough information to develop accurate algorithms, the project will spend another 5 years testing how reliable they are.

The project should help overcome a major problem with the studies done so far: Most of the data collected to generate personalized diets comes from people with European ancestry. This poses challenges for addressing diseases common among minority populations in the U.S., like diabetes and hypertension. But the NPH project hopes to change that. Its researchers have partnered with the All of Us Research Program, the NIH’s effort to build a health database that has 1 million people.

“All of Us has a focus on inclusion,” says Nicastro. “They're including a lot of groups of people that have been previously underrepresented in biomedical research. By partnering with them, we have the opportunity to make discoveries related to nutrition that are relevant to so many more people.”

Getting There

While  precision nutrition is now available only to people willing to pay a biotech company to do certain tests, it may someday transform the way we eat.

“What we'd like to see, if precision nutrition really is the way for everybody,” says Nicastro, “is for this to be open to patients and become the default in clinical practice.”


Show Sources

Nature Genetics: “Differences between germline genomes of monozygotic twins.”
Progress in Molecular Biology and Translational Science: “Fundamentals of Nutrigenetics and Nutrigenomics.”

James Marcum, PhD, professor of philosophy, Baylor University, Waco, TX.

Diabetes and Obesity: “Nutrigenetics/Nutrigenomics, Personalized Nutrition, and Precision Healthcare.”

Antonie van Leeuwenhoek: “Human gut microbiota/microbiome in health and diseases: a review.”

National Academies of Sciences, Engineering, and Medicine: “Challenges and Opportunities for Precision and Personalized Nutrition: Proceedings of a Workshop – in Brief.”

Cell: “Personalized Nutrition by Prediction of Glycemic Responses.”

Nature Medicine: “Microbiome connections with host metabolism and habitual diet from 1,098 deeply phenotyped individuals.”

National Institutes of Health: “NIH awards $170 million for precision nutrition study.”

Holly Nicastro, PhD, program director, National Institutes of Health.

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