The future of nutrition advice

By Lisa Drayer, CNN

Most of us know we should eat more fruits, vegetables and whole grains.

So why would the National Institutes of Health spend $150 million to answer questions such as “What and when should we eat?” and “How can we improve the use of food as medicine?”

The answer may be precision nutrition, which aims to understand the health effects of the complex interplay among genetics, our microbiome (the bacteria living in our gut), our diet and level of physical activity, and other social and behavioral characteristics.

That means that everyone could have their own unique set of nutritional requirements.

How is that possible? I asked three experts who conduct precision nutrition research: Dr. Frank Hu, professor of nutrition and epidemiology and chair of the Department of Nutrition at the Harvard T.H. Chan School of Public Health, and Martha Field and Angela Poole, both assistant professors in the division of nutritional sciences at Cornell University’s College of Human Ecology.

Below is an edited version of our conversation.

CNN: How is precision nutrition different from current nutrition advice?

Dr. Frank Hu: The idea of precision nutrition is to have the right food, at the right amount, for the right person. Instead of providing general dietary recommendations for everyone, this precision approach tailors nutrition recommendations to individual characteristics, including one’s genetic background, microbiome, social and environmental factors, and more. This can help achieve better health outcomes.

CNN: Why is there no one-size-fits-all prescription when it comes to what we should be eating?

Hu: Not everyone responds to the same diet in the same way. For example, given the same weight-loss diet, some people can lose a lot of weight; other people may gain weight. A recent study in JAMA randomized a few hundred overweight individuals to a healthy low-carb or low-fat diet. After one year, there was almost an identical amount of weight loss for the two groups, but there was a huge variation between individuals within each group — some lost 20 pounds. Others gained 10 pounds.

Martha Field: Individuals have unique responses to diet, and the “fine adjust” of precision nutrition is understanding those responses. This means understanding interactions among genetics, individual differences in metabolism, and responses to exercise.

CNN: How do we eat based on precision nutrition principles now?

Hu: There are some examples of personalized diets for disease management, like a gluten-free diet for the management of celiac disease, or a lactose-free diet if you are lactose intolerant. For individuals with a condition known as PKU (phenylketonuria), they should consume (a) phenylalanine-free diet. It’s a rare condition but a classic example of how your genes can influence what type of diets you should consume.

Angela Poole: If I had a family history of high cholesterol, diabetes or colon cancer, I would increase my dietary fiber intake, eating a lot of different sources, including a variety of vegetables.

Field: If you have high blood pressure, you should be more conscious of sodium intake. Anyone with a malabsorption issue might have a need for higher levels of micronutrients such as B vitamins and some minerals.

CNN: There is research showing that people metabolize coffee differently. What are the implications here?

Hu: Some people carry fast caffeine-metabolizing genes; others carry slow genes. If you carry fast (metabolizing) genotypes, you can drink a lot of caffeinated coffee because caffeine is broken down quickly. If you are a slow metabolizer, you get jittery and may not be able to sleep if you drink coffee in the afternoon. If that’s the case, you can drink decaf coffee and still get the benefits of coffee’s polyphenols, which are associated with decreased risk of heart disease and diabetes without the effects of caffeine.

CNN: How much of a role do our individual genes play in our risk of disease? And can our behavior mitigate our disease risk?

Hu: Our health is affected by both genes and diets, which constantly interact with each other because certain dietary factors can turn on or off some disease-related genes. We published research showing that reducing consumption of sugary beverages can offset the negative effects of obesity genes. That’s really good news. Our genes are not our destiny.

Another area of precision nutrition is to measure blood or urine metabolites, small molecules produced during the breakdown and ingestion of food. For example, having a higher concentration of branched-chain amino acids (BCAAs) strongly predicts one’s future risk of diabetes and cardiovascular disease. The blood levels of BCAAs depend on individuals’ diet, genes and gut microbiome. We found that eating a healthy (Mediterranean-style) diet can mitigate harmful effects of BCAAs on cardiovascular disease. So measuring BCAAs in your blood may help to evaluate your risk of developing diabetes and cardiovascular disease and encourage dietary changes that can lower risk of chronic diseases down the road.

Field: The environmental effects can sometimes be on the same magnitude as the genetic effects with respect to risk for disease.

CNN: Our individual microbiomes may be able to dictate what type of diet we should be consuming. Can you tell us about this emerging research? And what do you think of microbiome tests?

Poole: Research has shown that in some people, their blood sugar will spike higher from eating bananas than from eating cookies, and this has been associated with microbiome composition. Scientists have used microbiome data to build algorithms that can predict an individual’s glucose response, and this is a major advance. But that’s not an excuse for me to shovel down cookies instead of bananas. Likewise, if the algorithm suggests eating white bread instead of whole-wheat bread due to blood glucose responses, I wouldn’t just eat white bread all the time.

At the moment, I’m not ready to spend a lot of money to see what’s in my gut microbiome … and the microbiome changes over time.

Hu: Microbiome tests are not cheap, and the promise that this test can help develop a personalized meal plan that can improve blood sugar and blood cholesterol … at this point, the data are not conclusive.

CNN: How will nutrition advice be different 10 years from now?

Poole: I think you will receive a custom-tailored grocery list on an app — foods that you want to buy and foods that you want to avoid, based on your blood sugar responses to foods, your level of physical activity and more.

Hu: We will have more and better biomarkers and more affordable and accurate nutrigenomics and microbiome tests as well as better computer algorithms that predict your response to food intakes.

But these technologies cannot substitute general nutrition principles such as limiting sodium and added sugar and eating more healthy plant foods. In a few years, you may be able to get a more useful response from Alexa if you ask her what you should eat — but like other answers from Alexa, you’ll have to take it with a grain of salt.

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Lisa Drayer is a nutritionist, an author and a CNN health and nutrition contributor.