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.