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.
References:
- Ferrannini E, Gastaldelli A, Miyazaki Y, et al. Predominant role of reduced beta-cell sensitivity to glucose over insulin resistance in impaired glucose tolerance. Diabetologia. 2003;46(9):1211-1219.
- Gepts W. Pathologic anatomy of the pancreas in juvenile diabetes mellitus. Diabetes. 1965;14(10):619-633.
- Kahleova H, Mari A, Nofrate V, et al. Improvement in β-cell function after diet-induced weight loss is associated with decrease in pancreatic polypeptide in subjects with type 2 diabetes. Journal of diabetes and its complications. 2012;26(5):442-449.
- Solomon TP, Haus JM, Kelly KR, Rocco M, Kashyap SR, Kirwan JP. Improved pancreatic beta-cell function in type 2 diabetics following lifestyle-induced weight loss is related to glucose-dependent insulinotropic polypeptide. Diabetes care. 2010.
- Barnard ND, Cohen J, Jenkins DJ, et al. A low-fat vegan diet improves glycemic control and cardiovascular risk factors in a randomized clinical trial in individuals with type 2 diabetes. Diabetes care. 2006;29(8):1777-1783.
- Barnard ND, Gloede L, Cohen J, et al. A low-fat vegan diet elicits greater macronutrient changes, but is comparable in adherence and acceptability, compared with a more conventional diabetes diet among individuals with type 2 diabetes. Journal of the American Dietetic Association. 2009;109(2):263-272.
- McMacken M, Shah S. A plant-based diet for the prevention and treatment of type 2 diabetes. Journal of geriatric cardiology: JGC. 2017;14(5):342.
- Tonstad S, Butler T, Yan R, Fraser GE. Type of vegetarian diet, body weight and prevalence of type 2 diabetes. Diabetes care. 2009.
- Snowdon DA, Phillips RL. Does a vegetarian diet reduce the occurrence of diabetes? American Journal of Public Health. 1985;75(5):507-512.
- Vang A, Singh PN, Lee JW, Haddad EH, Brinegar CH. Meats, processed meats, obesity, weight gain and occurrence of diabetes among adults: findings from Adventist Health Studies. Annals of Nutrition and Metabolism. 2008;52(2):96-104.
- Yokoyama Y, Levin SM, Barnard ND. Association between plant-based diets and plasma lipids: a systematic review and meta-analysis. Nutrition reviews. 2017;75(9):683-698.
- Kahleova H, Tura A, Hill M, Holubkov R, Barnard ND. 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.
- Page KA, Reisman T. Interventions to preserve beta-cell function in the management and prevention of type 2 diabetes. Current diabetes reports. 2013;13(2):252-260.
- Kipnis V, Subar AF, Midthune D, et al. Structure of dietary measurement error: results of the OPEN biomarker study. American journal of epidemiology. 2003;158(1):14-21.