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How the Right Foods May Lead to a Healthier Gut, and Better Health

How the Right Foods May Lead to a Healthier Gut, and Better Health

A diet full of highly processed foods with added sugars and salt promoted gut microbes linked to obesity, heart disease and diabetes.

Credit…Getty Images
Anahad O’Connor

  • Jan. 11, 2021, 11:00 a.m. ET

Scientists know that the trillions of bacteria and other microbes that live in our guts play an important role in health, influencing our risk of developing obesity, heart disease, Type 2 diabetes and a wide range of other conditions. But now a large new international study has found that the composition of these microorganisms, collectively known as our microbiomes, is largely shaped by what we eat.

By analyzing the diets, health and microbiomes of more than a thousand people, researchers found that a diet rich in nutrient-dense, whole foods supported the growth of beneficial microbes that promoted good health. But eating a diet full of highly processed foods with added sugars, salt and other additives had the opposite effect, promoting gut microbes that were linked to worse cardiovascular and metabolic health.

The researchers found that what people ate had a more powerful impact on the makeup of their microbiomes than their genes. They also discovered that a variety of plant and animal foods were linked to a more favorable microbiome.

One critical factor was whether people ate foods that were highly processed or not. People who tended to eat minimally processed foods like vegetables, nuts, eggs and seafood were more likely to harbor beneficial gut bacteria. Consuming large amounts of juices, sweetened beverages, white bread, refined grains, and processed meats, on the other hand, was associated with microbes linked to poor metabolic health.

“It goes back to the age-old message of eating as many whole and unprocessed foods as possible,” said Dr. Sarah E. Berry, a nutrition scientist at King’s College London and a co-author of the new study, which was published Monday in Nature Medicine. “What this research shows for the first time is the link between the quality of the food we’re eating, the quality of our microbiomes and ultimately our health outcomes.”

The findings could one day help doctors and nutritionists prevent or perhaps even treat some diet-related diseases, allowing them to prescribe personalized diets to people based on the unique makeup of their microbiomes and other factors.

Many studies suggest that there is no one-size-fits-all diet that works for everyone. The new study, for example, found that while some foods were generally better for health than others, different people could have wildly different metabolic responses to the same foods, mediated in part by the kinds of microbes residing in their guts.

“What we found in our study was that the same diet in two different individuals does not lead to the same microbiome, and it does not lead to the same metabolic response,” said Dr. Andrew T. Chan, a co-author of the study and a professor of medicine at Harvard Medical School and Massachusetts General Hospital. “There is a lot of variation.”

The new findings stem from an international study of personalized nutrition called Predict, which is the world’s largest research project designed to look at individual responses to food. Started in 2018 by the British epidemiologist Tim Spector, the study has followed over 1,100 mostly healthy adults in the United States and Britain, including hundreds of identical and nonidentical twins.

The researchers collected data on a wide range of factors that influence metabolism and disease risk. They analyzed the participants’ diets, microbiomes and body fat. They took blood samples before and after meals to look at their blood sugar, hormones, cholesterol and inflammation levels. They monitored their sleep and physical activity. And for two weeks they had them wear continuous glucose monitors that tracked their blood sugar responses to different meals.

The researchers were surprised to discover that genetics played only a minor role in shaping a person’s microbiome. Identical twins were found to share just 34 percent of the same gut microbes, while people who were unrelated shared about 30 percent of the same microbes. The composition of each person’s microbiome appeared instead to be driven more by what they ate, and the types of microbes in their guts played a strong role in their metabolic health.

The researchers identified clusters of so-called good gut bugs, which were more common in people who ate a diverse diet rich in high-fiber plants — like spinach, broccoli, tomatoes, nuts and seeds — as well as minimally processed animal foods such as fish and full-fat yogurt. They also found clusters of “bad” gut bugs that were common in people who regularly consumed foods that were highly processed. One common denominator among heavily processed foods is that they tend to contain very little fiber, a macronutrient that helps to nourish good microbes in the gut, the researchers said.

Among the “good” strains of gut microbes were Prevotella copri and Blastocystis, both of which were associated with lower levels of visceral fat, the kind that accumulates around internal organs and that increases the risk of heart disease. These microbes also appeared to improve blood sugar control, an indicator of diabetes risk. Other beneficial microbes were associated with reduced inflammation and lower spikes in blood fat and cholesterol levels after meals, all of which play a role in cardiovascular health.

The new study was funded and supported by Zoe Global, a health science company, as well as by the Wellcome Trust, a British nonprofit, and several public health groups.

Dr. Berry said the findings suggest that by looking at microbiome profiles they can identify people at high risk of developing metabolic diseases and intervene early on. She and her colleagues are now planning a clinical trial that will test whether telling people to change specific foods in their diets can alter levels of good and bad microbes in their guts and subsequently improve their health.

“We think there are lots of small changes that people can make that can have a big impact on their health that might be mediated through the microbiome,” she said.

How to Sell Kids on Vegetables

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Credit Damon Winter/The New York Times

The same marketing techniques used to convince children to eat junk food are highly effective in promoting fruits and vegetables, a new study has found.

Researchers assigned 10 elementary schools to one of four groups. In the first, they posted vinyl banners around the salad bar depicting cartoon vegetable characters with “super powers.” In the second, they showed television cartoons of the characters. The third got both cartoons and banners, and a control group got no intervention. The study, in Pediatrics, went on for six weeks in 2013.

Compared to control schools, TV segments alone produced a statistically insignificant increase in vegetable consumption. But in schools decorated with the banners alone, 90.5 percent more students took vegetables. And where both the banners and the TV advertisements were used, the number of students taking vegetables increased by 239.2 percent.

“A lot of people have pushed back on this, saying marketing is evil,” said one of the authors, David R. Just, a professor of applied economics at Cornell. “But I have to disagree. It’s possible to use marketing techniques to do some good things.”

Putting such programs into practice, Dr. Just said, presents problems. “Schools are left to do their own marketing, and that’s not cost effective. These need to be national programs. McDonald’s is effective because you see their marketing everywhere.”

A Few More Vegetables and a Little Less Meat May Reduce Diabetes Risk

Photo

Credit Justin Mott for The New York Times

You don’t have to be a vegetarian to reap the benefits of a plant-based diet.

New research shows that eating a few extra servings of healthy plant-based foods each day and slightly reducing animal-based foods like meat and dairy products can significantly lower your risk of Type 2 diabetes.

The findings are based on an analysis of the eating patterns of 200,000 men and women from three long-term studies who reported on their diets repeatedly over the course of two decades, and were published this week in PLOS Medicine.

The studies — the Nurses’ Health Study, the Nurses’ Health Study 2 and the Health Professionals Follow-Up Study — asked participants to fill out more than 100 detailed questions about their eating habits. They provided information not just about the foods they ate but about how the food was prepared and even what cooking oils were used.

While self-reported dietary information can be flawed, extra steps were taken to confirm the data. Participants completed questionnaires every two to four years, and the nutrient intake information was compared to tests of blood biomarkers to make sure they matched up. The results were also adjusted, or modified, to account for other characteristics that contribute to Type 2 diabetes, like being overweight.

The research was also unusual in that it distinguished between healthful and unhealthful plant-based foods. Healthful plant-based foods include whole grains, fruits, vegetables nuts, seed and legumes, while an unhealthful plant-based diet could include refined carbohydrates like bagels and muffins, starchy vegetables like potatoes and French fries and sugary foods like cake and cola. Animal-based foods include meat of all kinds, fish and seafood as well as eggs, dairy products and animal fats like butter.

On average, adults who ate a plant-based diet with few animal products cut their risk of Type 2 diabetes by 20 percent. But when researchers distinguished between healthful and unhealthful plant-based foods, they found that diabetes risk dropped by 34 percent among the healthful plant-based eaters. Notably, there wasn’t a benefit to plant-based eating when a person consumed a lot of refined carbohydrates and starchy vegetables. In that case, a person’s risk of developing Type 2 diabetes increased slightly.

While most American adults are omnivores, eating from many different food sources, and few are vegetarian, the research suggests that simply reducing the amount of animal-based food you eat from five or six servings a day to about four servings a day can lower the incidence of Type 2 diabetes. When people make these changes in diet, they usually cut back on red meat and processed meats and substitute healthier plant-based foods, including protein-rich ones like nuts, seeds and legumes, said Frank Hu, the study’s senior author and a professor at Harvard’s T.H. Chan School of Public Health.

“What we’re talking about is a moderate shift – replacing one or two servings of animal food a day with one or two plant-based foods,” said Dr. Hu. “We’re not talking about a dramatic change from being a carnivore to being vegan or even vegetarian – we’re talking about a small shift, that’s doable for most people. You can still include some meat, but not have it in the center of the plate.”

Good plant-based foods are known to be rich in fiber, antioxidants, good fats and a wide array of micronutrients, and have been shown to improve glucose metabolism and lower inflammatory markers. But scientists say they also help promote the good-for-you bacteria that live in your gut.

“When we ingest food, we’re feeding ourselves, but we’re also feeding the bacteria in our gut,” said Dr. Hu. “If you switch from an animal-based dietary pattern to a plant-based pattern, after a while – I don’t know how long it would take, a few weeks or months – the type of bacteria will also change.”

The bacteria in the gut use components of plant-based foods like fiber for their own survival and growth. These components are metabolized by the intestinal bacteria, and the end products are short-chain fatty acids, which have been shown to have beneficial effects on inflammation, insulin resistance and overall metabolism. They also may send a satiety signal to the brain, so people feel fuller.

When you eat refined carbohydrates and have less fiber in the diet, the healthy bacteria that metabolize fiber will be reduced, “so you won’t have the short-chain fatty acids that would have beneficial effects in your body,” Dr. Hu said.

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