Can science help customize your diet?

Those of us who have a friend who can eat sugary foods every day and not gain an ounce or a relative who has developed heart disease despite avoiding saturated fats know that one-size-fits-all dietary recommendations don’t reflect how differently we respond to food. But now one of the most comprehensive and ambitious new studies on diets could change that, producing insights that will eventually allow experts to tailor their recommendations for different people.

Starting this spring, 13 sites across the United States will begin enrolling 10,000 people of varying ages and weights to better identify important factors involved in so-called micronutrition. Specific efforts will be made to include those who are often overlooked in nutrition science: seniors over 65, people of color, rural people, people with disabilities, and sexual minorities.

During the first phase of the research, which will last two weeks, everyone will be instructed to eat as they normally would. In the second phase, 1,500 people will be allocated meals from several meals that will be sent directly to their homes. In the final phase, 500 people selected from the largest group will eat while they stay in a research center for two weeks. The latter is a large number for a controlled dietary study, which usually includes a few dozen participants, says Holly Nicastro, who will coordinate this $170 million National Institutes of Health research program called Nutrition for Precision Health. Participants will be drawn from the National Institutes of Health all of us Health Research Program, which anyone can join.

This large and diverse effort will “bring us one step closer to providing more accurate nutrition recommendations to groups of individuals,” says Sai Krupa Das, a metabolic scientist at Tufts University, one of six research centers that coordinate the registry sites.

How will the study work?

During the study, the researchers will regularly perform urine and blood tests and complete a census of each person’s gut microbiome — the trillions of organisms that permanently reside in the digestive tract. Participants will wear glucose monitors to record the rise and fall of blood sugar levels – a sign of how well the body processes carbohydrates and an important indicator of health. Daily behaviors such as sleep, stress, and the times people eat, among other factors, will also be tracked.

The new study will change our understanding of human diets because it differs fundamentally from how most nutrition studies are conducted, says Diana Thomas, professor of mathematics at the US Military Academy at West Point, who is involved in the research. Nutrition scientists generally examine a single nutrient in a homogenous population, inquiring, for example, whether blueberries lower the risk of cardiovascular disease in Americans (the answer to this still remains to be seen). unclear). In this study, she says, we didn’t start with a hypothesis, but rather “we wonder, what are the factors involved?”

The goal is to tease out the many variables that influence dietary responses and to develop algorithms that predict them, allowing dietitians to provide dietary advice to others with similar characteristics.

Das says making more targeted recommendations is critical to improving public health. The current approach has led many people to adjust expert nutritional advice, whether because the advice changes frequently (Traditional paradigm: eggs bad; Eggs are good) or because they tried a recommended way of eating and found it wasn’t ideal for them. “Exact nutrition will allow us to do better than the advice of a one-size-fits-all diet, which is the Mediterranean diet. Alternatively, we might say, ‘If you have certain ethnicities, characteristics, and physical responses to foods, this diet may be more appropriate. This is the step we are approaching.

Das cautions that the new advice derived from the research will not reach the level of the individual, which is why experts prefer the term micronutrition over another widely used term, personalized nutrition.

The study will focus on eating for optimal health rather than weight loss, but the two go hand in hand, Das says. “We don’t do calorie-restricted diets, but I think the response in terms of trying to improve metabolism will help with weight management as well.”

Genes versus the microbiome

Several decades of research has yielded clues about what constitutes public health.

One of these factors is genetics. The field was previously called nutritional genomics, but the field fell out of favor when it became clear that genes play a less prominent role in how the body responds to food than first thought, says Jose Ordovas, director of nutrition and genomics at Tufts University.

In a small number of cases, scientists have linked a specific gene to a direct health effect. The CYP1A2 gene, for example, is almost single-handedly responsible for determining how quickly enzymes metabolize caffeine in the liver. Genetic differences determine whether an evening cup of coffee keeps a person up all night or still allows them to get a restful night’s sleep. It also affects whether coffee will help a person exercise at a higher intensity, ie Ride a bike faster.

“Genetics is involved, but it won’t give us predictive equations to individualize the recommendations, because there are so many other factors involved,” Ordovas says. Since many of these factors, especially behavior, are easier to change than our genes, understanding them should lead to more effective approaches to improving health, he says.

Hundreds of studies have shown that the microbiome — the bacteria, fungi, parasites, and viruses found in the gut — is a critical factor in how the body processes food. consuming artificial sweeteners, for example, Change Microbiome composition and function in a way that increases glucose intolerance in healthy subjects. and some intestinal microbes persist in obese mice following a diet, which primes them—and perhaps us—to regain weight.

There is still a lot to learn about the microbiome, including optimal composition, how microbes work synergistically and how lifestyle affects this community, says Eran Elinav, chair of immunology at Israel’s Weizmann Institute of Science and a prolific researcher on the microbiome.

How lifestyle affects the way we process food

One of the hardest things about figuring out each person’s ideal diet is the complex interplay of genome, microbiome, and lifestyle factors—the latter of which scientists call the exposome.

Elinav says one of these lifestyle factors is when we eat dinner. His lab determined that the gut microbiome adheres to a circadian rhythm, with microorganisms built predictably. changing Their numbers and functions over a 24-hour period. They do this by responding to cues from sleeping and eating behaviours.

“When we disrupt our sleep-wake patterns with shift work or jet lag, one of the first things that happens is that this disrupts the daily activity of our microbes,” says Ellinav. Increased rates of obesity, type 2 diabetes, and cancers are linked to people with chronically disrupted sleep and eating schedules. turning off of this change in the microbiome, studies in mice suggest.

Lack of sleep, along with extreme stress, also disrupts metabolism and has other negative health effects even in people who eat a healthy diet, says Tufts Dass.

The NIH’s precision nutrition research will be the most comprehensive effort to use genes, microbes, and display to understand and predict nutritional responses to foods, but it won’t be the first. Several previous studies paved the way.

One effort, led by Elinav’s lab Published in the journal cell in 2015, which involved providing identical meals to 800 people and continuously monitoring their blood glucose levels. The week-long study revealed that glucose responses among participants differed significantly after each meal. The researchers note that the composition of their microbiome played a major role in determining that response, but that other factors were inevitably involved.

A few years later, a large study in the United Kingdom sought to expand knowledge of the variables involved in the game. Personal Responses to a Dietary Composition Experiment, or PREDICT, called the research concerned A thousand adults — including some genetically identical twins — had their gut microbiota, blood lipids, post-meal glucose levels, inflammation, and other factors monitored for two weeks. Ordovas, one of the study’s co-authors, says that tracking blood glucose throughout the day was again an important component. This continuous monitoring enabled the researchers to measure the effects of specific foods.

Here too, on a grand scale differences appeared to indicate that the participants’ bodies were processing the same nutrients differently. Genetic factors have proven to have a modest effect, but the results show how complex the digestive system can be. Some intestinal microbes – incl Prevotella Cobre And Blastocystis– were more important than genes in the processing of certain foods – but both still represent only a small part of the overall differences.

The goal of the upcoming NIH research is to better understand the factors that explain these differences. The hope is that this will enable people to adjust their lifestyle, diet, and possibly their gut microbes to improve their bodies’ responses to various nutrients. (Whether manipulation of the microbiome, for example through dietary changes, has a lasting effect remains to be seen unclear.)

For now, Das says the best nutritional advice she and others give stick to the basics: Fill your plate with high-fiber vegetables and fruits and avoid heavily processed foods in favor of whole foods.

“In the next five to 10 years there will be massive changes in how we look at food systems,” predicts Thomas of West Point. “Once the results of the NIH study start coming in, we’ll only know so much.”

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