In overweight adults with no history of diabetes, a low-fat, plant-based vegan diet has been shown to improve beta-cell function and insulin sensitivity, according to new research published in the journal Nutrients. 1
Accessing the function of beta cells, which store and release insulin, can help determine the risk for future type 2 diabetes.
In the study, researchers put 73 participants in a 16-week randomized controlled trial. Half consumed a low-fat vegan diet based on fruits, whole grains, and legumes with no calorie limit. The control group made no dietary changes.
The vegan diet provided 75% of caloric energy from carbohydrates, 15% from protein and 10% from fats.
Participants who ate a vegan diet significantly improved their metabolic function and showed a decrease in blood sugar levels both while fasting and during meal tests.
About 30 million Americans have type 2 diabetes and about 84 million have prediabetes, says Hana Kahleova, MD, PhD, the director of clinical research at the nonprofit Physicians Committee for Responsible Medicine and lead author of the research.
“This study has important applications for diabetes prevention,” says Dr. Kahleova. “Eating a vegan diet offers hope for people who are at a high risk of getting diabetes or have a family history of diabetes or who are simply overweight. The applicability of the study is huge.”
Often, by the time people get diabetes, about half of their beta cell function is gone, which means that the functional capacity of beta cells are already exhausted, she says.
“While this process has been shown to be partially reversed after bariatric surgery even for people with diabetes, our study shows that we can reverse this beta cell depletion through a vegan diet,” she says.
Although participants in the study did not have diabetes, many had high cholesterol and high blood pressure, both of which were lowered by the vegan diet. Although there were no caloric restrictions in the vegan diet, participants dropped an average of 15 pounds.
For some people, a vegan diet may appear too restrictive, but Dr. Kahleova maintains that, “if you make only small dietary changes, you can only expect small health changes.
“Knowing that this diet can reverse heart disease and beta cell dysfunction, you might approach the process in a different way: “OK, this diet can really work, how can I make it work in my life?”
Prior studies have shown that plant-based diets not only have the power to prevent and reverse type 2 diabetes but that they also lead to weight loss, improved cholesterol levels, lower blood pressure and less heart disease.
For people with diabetes, switching from a low carbohydrate diet to a vegan diet might cause “several blood sugar readings to be higher if you are taking a higher load of carbohydrates than you are used to,” says Dr. Kahleova. “But adaptation is very fast and blood sugars go much lower as the diet continues.”
Because a vegan diet might cause sugars to drop precipitously, the researcher urges patients to consult with an endocrinologist before making the switch.
“The important thing is how best to healthfully lose weight,” she says.
“Restrictive diets don’t work in the low run, our hunger is often stronger than our desire to get healthier. A vegan diet using low energy dense foods enables us to be satisfied with the meal and at the same time lose weight.”
“We know from many studies that vegan diets are very healthy,” says Emmy Suhl, MS, RD, LDN, CDE, a registered nutritionist and certified diabetes educator at the Joslin Diabetes Center. “Vegan diets have been compared to other diets—lacto-ovo, pescatarian, omnivore—and people who follow a vegan diet are generally healthier.”
“One of the hot topics now is the microbiome and diabetes,” she says. “It appears that our diets affect the microbiome, the genetic material
in our gut that encompasses mostly bacteria but also viral and other microorganisms. More and more research shows that changing our diets can change our microbiome, our metabolism and our sensitivity to insulin and the functioning of our beta cells.”
“You can’t have a healthy microbiome without plant-based foods, because microorganisms survive on the fiber of these foods,” she says.
While people with type 2 diabetes may have been told to stay away from carbohydrates, Suhl notes that healthy complex carbohydrates are only found in plant-based foods.
“If the goal is to be healthy, it has been established that a 150-pound person needs at least 130 grams of carbohydrates per day for running internal organs,”2 she says. “There are vitamins and minerals and phytochemicals that are only found in plant foods.”
“By concentrating on low-glycemic types of carbohydrates people with diabetes can eat carbohydrates,” she adds. “Just don’t eat them in large quantities.”
Suhl notes that losing weight is not always associated with a healthy diet— that people with diabetes also need to watch high lipid levels and other markers of cardiovascular disease.
“You don’t need to become a complete vegan and exclude all animal products,” she adds. “It’s not all or nothing. Eating a plant-based diet plus moderate amounts of animal foods—lean fish, shellfish, lean poultry or even lean beef —can be part of a healthy diet for people with diabetes.”