Vegetarian Dietary Patterns: Mortality, Colorectal Cancer, and Food Consumption

Objective Vegetarian dietary patterns represent longstanding, real-world diets consumed by a minority of persons. Studies of important health outcomes of such diets, particularly for all-cause mortality and colorectal cancer risk, have yielded inconsistent results. We sought to examine these outcomes (mortality and colorectal cancer incidence) in a large North-American cohort. We also sought to further characterize potentially important differences in the food consumption patterns of these diets. Design Baseline diet was measured by a quantitative food frequency questionnaire among more than 96,000 Seventh-day Adventists in the US and Canada, enrolled from 2002-2007. Dietary patterns were defined, based on the reported consumption of key foods, along a continuum of animal food avoidance. Mortality through 2009 was obtained by record linkage with the National Death Index. Cancer incidence data through 2011 was obtained by record linkage with state cancer registries. Cox regression of time-to-event was used as the primary analytic approach for both mortality and colorectal cancer incidence outcomes. Results Vegetarian dietary patterns demonstrated reduced consumption of sweets, added fats, refined grains, and caloric beverages and increased consumption of a variety of plant foods. Vegetarian dietary patterns together were associated with a reduction in risk of all-cause mortality (HR=0.88, 95% CI 0.80-0.97). Reductions were seen for vegans, lacto-ovo-vegetarians, and pesco-vegetarians separately. Effects were stronger in men. Some beneficial associations were seen for cardiovascular, renal, and endocrine cause of mortality but not for cancer mortality. Vegetarian dietary patterns were also associated with a reduction in colorectal cancer incidence (HR=0.79, 95% CI 0.65-0.95). Conclusion Vegetarian dietary patterns in the Adventist Health Study 2 are associated with reduced all-cause mortality and reduced incidence of colorectal cancers. These diets demonstrate notable differences in the consumption of a variety of food groups, beyond those animal foods which define them