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Plant-based diet improves beta-cell function, insulin sensitivity in obesity
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HOUSTON — Adults with overweight or obesity assigned to a vegan diet for 16 weeks experienced improvements in beta-cell function and insulin sensitivity vs. similar adults assigned to a control diet, according to study data presented at the American Association of Diabetes Educators annual meeting.
“An ideal diet for type 2 diabetes would address the key pathophysiologic mechanisms behind the disease, which is the insulin resistance and beta-cell dysfunction,” Hana Kahleova, MD, PhD, director of clinical research with the Physicians Committee for Responsible Medicine in Washington, D.C., told Endocrine Today. “Right now, regardless of the medication that you use, beta-cell function and mass keep declining over time. That is why we looked into the mechanisms behind a plant-based diet, which has been shown to reduce the risk for type 2 diabetes and is shown to be effective in the treatment of diabetes.”
In a single-center, randomized study, Kahleova and colleagues analyzed data from adults with a BMI between 28 kg/m² and 40 kg/m² but without diabetes, recruited between October 2016 and June 2017 (mean age, 53 years; 89% women; mean BMI, 33.4 kg/m²). Participants were asked to follow a low-fat vegan diet consisting of vegetables, grains, legumes and fruits (75% of energy from carbohydrates, 15% protein, 10% fat; no meals provided; n = 38) or instructed to make no diet changes (controls; n = 37). Alcoholic beverages were limited to one per day for women and two per day for men in both groups. To monitor adherence, participants completed a 3-day dietary record at baseline and again at 16 weeks. Insulin secretion was assessed after stimulation with a liquid breakfast; plasma glucose, immunoreactive insulin and C-peptide were measured at 0, 30, 60, 120 and 180 minutes. Primary outcome was beta-cell function from baseline to 16 weeks; secondary outcome was insulin resistance as measured by homeostasis model assessment of insulin resistance (HOMA-IR).
Researchers observed a marked increase in meal-stimulated insulin secretion in the vegan diet group vs. controls (interaction between group and time, P < .001). HOMA-IR fell significantly in the vegan diet group (treatment effect, 1; 95% CI, 1.2 to 0.8). Changes in HOMA-IR correlated positively with changes in BMI (P = .009) and visceral fat volume (P = .001).
The researchers noted that changes in glucose-induced insulin secretion correlated negatively with BMI changes (P = .04), but not with changes in visceral fat.
“We have shown that even 16 weeks on a plant-based diet can improve the beta-cell function, which is exciting,” Kahleova said. “We were expecting to see a slowing down of the progressive decline of beta-cell function. We did not expect to see an improvement. It was striking.”
Kahleova said diabetes educators can work with patients to achieve greater results when intervening earlier in the course of disease.
“With prediabetes or the early stages of type 2 diabetes, beta-cell function is more preserved, and there is a high probability of reversal with a plant-based diet,” Kahleova said. “Of course, we’re not expecting that everyone will want to do it. Not everyone wants to cook a new way, but it is more about personal choice and the willingness to experiment. Try new recipes, new foods. You just need to be open to it.
“This is an exciting message for educators, who can aim for a complete reversal of diabetes in their patients,” Kahleova said. – by Regina Schaffer
References:
Kahleova H, et al. P311. Presented at: American Association of Diabetes Educators; Aug. 9-12, 2019; Houston.
Kahleova H, et al. Nutrients. 2018;doi:10.3390/nu10020189.
Disclosures: The authors report no relevant financial disclosures.
Perspective
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Frank Qian, MPH
This is an important interventional study that provides insights into the potential mechanisms underlying prior and recent long-term epidemiological studies demonstrating a reduced risk for diabetes in individuals who adhere more closely to a plant-based dietary pattern, particularly ones that emphasize healthful plant-based foods, such as fruits, vegetables, legumes and whole grains. Moreover, the effect on insulin resistance and beta-cell function was observed independently of BMI, highlighting how crucial diet quality is in the prevention of metabolic diseases. It would be interesting and vital to conduct longer-term studies using this type of interventional diet to assess certain parameters of glucose-insulin homeostasis, such as HbA1c. In this case, the trial duration may have been too short to demonstrate any appreciable differences between the two groups. Overall, this study shows there is great promise for further clarifying nutritional targets for the primary prevention of type 2 diabetes.
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