Abstract

Objective: We assessed the prevalence of type 2 diabetes in people following different types of vegetarian diets compared to non-vegetarians.

Research Design and Methods: Study participants were 22 434 men and 38 469 women who participated in the Adventist Health Study-2 conducted in 2002-6. We collected self-reported demographic, anthropometric, medical history and lifestyle data from Seventh day Adventist church members across North America. The type of vegetarian diet was categorized based on a food frequency questionnaire. We calculated odds ratios (ORs) and 95% confidence intervals (CIs) using multivariate-adjusted logistic regression.

Results: Mean BMI was lowest in vegans (23.6 kg/m²) and incrementally higher in lacto-ovo vegetarians (25.7), pesco vegetarians (26.3), semi-vegetarians (27.3) and non-vegetarians (28.8). Prevalence of type 2 diabetes increased from 2.9% in vegans to 7.6% in non-vegetarians; prevalences were intermediate in participants consuming lacto-ovo (3.2%), pesco (4.8%) or semi-vegetarian (6.1%) diets. After adjustment for age, gender, ethnicity, education, income, physical activity, TV watching, sleep habits, alcohol use and BMI, vegans (OR 0.51, 95% CI 0.40-0.66), lacto-ovo vegetarians (OR 0.54, 95% CI 0.49-0.60), pesco vegetarians (OR 0.70, 95% CI 0.61-0.80) and semi-vegetarians (OR 0.76, 95% CI 0.65-0.90) had a lower risk of type 2 diabetes than non-vegetarians.

Conclusions: The five unit BMI difference between vegans and non-vegetarians indicates a substantial potential of vegetarianism to protect against obesity. Increased conformity to vegetarian diets protected against risk of type 2 diabetes after lifestyle characteristics and BMI were taken into account. Pesco and semi-vegetarian diets afforded intermediate protection.