Vegan Diet Bests ADA Plan at Diabetes Control

WASHINGTON, Aug. 9 -- The Physicians Committee for Responsible Medicine, a crusading group that has long ranked vegetarianism high on its agenda, has made a compelling case for a low-fat vegan diet to improve glycemic control.

Both a low-fat vegan diet and a diet following American Diabetes Association guidelines improved glycemic control and cardiovascular risk factors in patients with type 2 diabetes, found a 22-week study partially funded by NIH and published in the August issue of Diabetes Care.

But the vegan diet was better, reported Neal D. Barnard, M.D., an adjunct associate professor of medicine at George Washington University, who is president of the Physicians Committee for Responsible Medicine, and colleagues.

The vegan diet -- consisting of fruits, vegetables and grains but no animal products and only limited added fats -- did a better job of lowering glycated hemoglobin (HbA1C) levels, body weight, and LDL, reported Dr. Barnard.

The authors compared results among patients with type 2 diabetes assigned to either a vegan diet or one that adhered to ADA guidelines. The rationale for the study was to determine, independent of exercise, whether low-fat vegan diets could significantly improve glycemic control and reduce cardiovascular risk factors, Dr. Barnard and colleagues wrote.

"Diabetes prevalence is relatively low among individuals following plant-based and vegetarian diets, and clinical trials using such diets have shown improvements in glycemic control and cardiovascular health," the authors said. "Most of these trials have also included exercise, thus making it impossible to isolate diet effects."

Previously, Dr. Barnard was co-author of a 12-week pilot trial of a low-fat vegan diet in people individuals with type 2 diabetes who did not increase their exercise levels (if any) during the trial. The authors found that fasting serum glucose concentrations dropped 28% compared with 12% in the control group following a diet based on ADA guidelines (P

Among all patients, 43% (21 of 49) of the vegan group and 26% (13 of 50) of the ADA group were able to reduce their diabetes medications. A1C levels dropped by 0.96% in the vegan diet group, compared with 0.56% in the ADA diet group, a difference that was not significant (P=0.089).

Among patients who did not change diabetes medications during the study, however, A1C decreased by 1.23% in the vegan group, compared with 0.38% in the ADA group (P=0.01).

Participants in both groups lost weight, but patients on the vegan diet lost twice as much as those on the ADA diet-6.5 kg (14.3 lbs) compared with 3.1 kg (6.82 lbs), respectively.

The change in body weight correlated with decreases in HbA1C change (r=0.51, n=57, P

The authors acknowledged that the analysis of HbA1C changes was confounded by the fact that both diets made patients more susceptible to hypoglycemic effects from their medications, resulting in medication reductions. This meant that the analysis of HbA1C changes could only be carried out in patients whose medications were unchanged throughout the study.

In addition, most study participants were taking antihypertensive agents, making it difficult to interpret a potential effect of diet on blood pressure.