Plant-Based Diet Improves Beta-Cell Function and Insulin Resistance in Overweight Adults

Written by Angeline A. De Leon, Staff Writer. Overweight non-diabetic subjects, who participated in a 16-week low-fat plant-based diet consisting of vegetables, grains, legumes, and fruits, significantly increased their beta-cell function and fasting insulin sensitivity compared to the control group.

Pancreatic beta-cells are primarily responsible for producing, storing, and releasing insulin. Impaired function of beta-cells is associated with development of type 2 diabetes ¹, and at the time of disease onset, an estimated 70-90% of beta-cell mass is lost in diabetic patients ². Previous research has shown that beta-cell function may be improved in diabetic individuals through energy-restricted dieting ^3,4, but clinical improvement of glycemic control through dietary intervention is not dependent on caloric restriction alone. When compared to a calorically-restricted, carbohydrate-controlled diet, a vegan diet has been shown to lead to greater improvement of glycemic control in type 2 diabetes patients ^5,6. Research indicates that implementation of a plant-based diet (legumes, fruits, vegetables, nuts, and whole grains) can help prevent and ameliorate symptoms of type 2 diabetes ⁷. Individuals following a plant-based diet, in comparison to non-vegetarians, show a significantly lower incidence rate of diabetes ^8-10 and also benefit from improvements in total cholesterol, low-density lipoprotein (LDL) cholesterol, and high-density lipoprotein (HDL) cholesterol ¹¹. In a 2018 study ¹² published in Nutrients, researchers examined the potential benefits of a plant-based dietary intervention on beta-cell function and insulin resistance in overweight adults.

A total of 75 participants (aged 25 to 75 years) with a body mass index between 28 and 40 kg/m² (and no history of diabetes) were enrolled in a single-center, randomized, open parallel study. Subjects were randomly allocated to follow a low-fat vegan diet (about 75% carbohydrates, 15% protein, and 10% fat) consisting of vegetables, grains, legumes, and fruits or to make no diet changes for 16 weeks. Participants were asked to complete a 3-day dietary record to track adherence. At baseline and at the end of 16 weeks (on an outpatient basis), insulin secretion was measured following a standard meal test, and plasma concentrations of glucose, immunoreactive insulin, and C-peptide were analyzed, as well as plasma lipid concentrations. Beta-cell function was calculated using insulin secretory rates, and insulin resistance was determined using the Homeostasis Model Assessment Index (HOMA-IR).

At the end of the intervention period, subjects on the vegan diet demonstrated significant decreases in body mass index, fat mass, and visceral fat volume (group x time, p < 0.001 for all). The intervention group also showed significant decreases in total cholesterol (gxt, p = 0.02), LDL cholesterol (gxt, p = 0.03), HDL cholesterol (gxt, p = 0.002), fasting plasma glucose (gxt, p < 0.001), insulin (gxt, p = 0.05), and C-peptide (gxt, p = 0.003). In terms of beta-cell function, the vegan group, relative to controls, showed a marked dose-response increase in insulin secretion as a function of plasma glucose concentrations (gxt, p < 0.001). HOMA-IR significantly diminished as well in the vegan group (p < 0.001), and changes in HOMA-IR showed a positive correlation with changes in BMI (r = 0.34, p = 0.009) and volume of visceral fat (r = 0.42, p = 0.001).

Findings indicate that adoption of a low-fat, vegan diet can elicit meaningful improvements in beta-cell function, insulin sensitivity, and plasma lipid profile in overweight individuals. Evidence is in line with previous research suggesting that beta-cell function can be boosted by therapies facilitating reduction of body fat ¹³. Improving quality of macronutrient intake appears to be a viable strategy for supporting healthy BMI and beta-cell function in overweight individuals without a history of diabetes. One limitation noted by the authors of the study involves the use of self-report diet records, which are known to have substantial subject-specific bias ¹⁴.

Source: Kahleova H, Tura A, Hill M, et al. A plant-based dietary intervention improves beta-cell function and insulin resistance in overweight adults: a 16-week randomized clinical trial. Nutrients. 2018; 10(2): 189. DOI: 10.3390/nu10020189.

Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

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Posted November 5, 2018.

Angeline A. De Leon, MA, graduated from the University of Illinois at Urbana-Champaign in 2010, completing a bachelor’s degree in psychology, with a concentration in neuroscience. She received her master’s degree from The Ohio State University in 2013, where she studied clinical neuroscience within an integrative health program. Her specialized area of research involves the complementary use of neuroimaging and neuropsychology-based methodologies to examine how lifestyle factors, such as physical activity and meditation, can influence brain plasticity and enhance overall connectivity.

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