PCRM Study on Insulin and Vegan Diets

Thank you to our intern, Shelby Stevens, for summarizing this article. Shelby will be helping us out with VeganHealth.org throughout the summer.
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In response to a meal, beta-cells in the pancreas release insulin to help move glucose (sugar) from the blood to the muscles and organs. Beta-cell dysfunction, as well as the inability of the body to respond properly to insulin (called insulin resistance), are critical factors in the development of type 2 diabetes, which is characterized by high blood sugar.

The Physicians Committee for Responsible Medicine (PCRM) funded a 16-week, randomized, controlled study to determine the effects of a low-fat, vegan diet on insulin resistance and the function of beta-cells (1).

Adults who were classified as overweight or obese without histories of diabetes were randomly assigned to follow either a low-fat vegan diet (38 participants) or continue their current diets with no changes (37 participants). The vegan diet group was instructed to eat vegetables, grains, legumes, and fruits. Calories comprised of 75% carbohydrate, 15% protein, and 10% fat.

Compared with the control group, the vegan diet group experienced an improvement in beta-cell function and a decrease in fasting insulin resistance, body mass index, body fat, and fat around internal organs (visceral fat).

The loss of visceral fat, in particular, may partially explain the decrease in insulin resistance, as this type of fat releases hormones that affect metabolism. The improvement in beta cell function, represented by meal-induced insulin secretion, was associated with the reduction in body mass index.

Although neither group was told to limit their food intake, both groups reduced their caloric intake during the study. Those in the vegan diet group did not reduce their mean calorie intake beyond that of their counterparts, but their fiber and carbohydrate intake increased while their protein, cholesterol, and fat decreased.

These results demonstrate that altering macronutrient composition through a vegan diet, without restricting calories, can improve beta-cell function and fasting insulin resistance in adults who are overweight or obese but with no history of diabetes.

For more information, see Type 2 Diabetes and Vegan Diets.

References

1. Kahleova H, Tura A, Hill M, Holubkov R, Barnard N. A plant-based dietary intervention improves beta-cell function and insulin resistance in overweight adults: a 16-week randomized clinical trial. Nutrients. 2018 February;10(2).