Vegetarian Dietary Patterns and Mortality in Adventist Health Study 2

Study Questions:

Do vegetarian dietary patterns reduce risk of mortality?

Methods:

This was a prospective cohort study using the Adventist Health Study, a large North American Cohort. A total of 96,469 Seventh-day Adventist men and women were recruited between 2002 and 2007, from which an analytic sample of 73,308 participants were included in the present analysis. Participants were excluded for missing data for questionnaire return date, birth date, sex, or race; age younger than 25 years; estimated energy intake <500 kcal/d or >4500 kcal/d; improbable response patterns or >69 missing values in dietary data; non-US residents; or history of a specific prior cancer diagnosis (except nonmelanoma skin cancers) or of cardiovascular disease. Diet was assessed at baseline by a quantitative food frequency questionnaire and categorized into five dietary patterns: nonvegetarian, semi-vegetarian, pesco-vegetarian, lacto-ovo–vegetarian, and vegan. The primary outcomes of interest were all-cause, and cause-specific deaths through 2009 were identified from the National Death Index.

Results:

Among the 73,308 individuals in the cohort, 5,548 (7.6%) were vegans, 21,177 (28.9%) were lacto-ovo–vegetarians, 7,194 (9.8%) were pesco-vegetarians, 4,031 (5.5%) were semi-vegetarians, and 35,359 (48.2%) were nonvegetarians. Vegetarian groups tended to be older, more highly educated, and more likely to be married, to drink less alcohol, to smoke less, to exercise more, and to be thinner. The proportion of blacks was highest among pesco-vegetarians and lowest in lacto-ovo–vegetarians. Of postmenopausal women, far fewer vegans were receiving hormone therapy. There were 2,570 deaths among 73,308 participants during a mean follow-up time of 5.79 years. The mortality rate was 6.05 (95% confidence interval [CI], 5.82-6.29) deaths per 1,000 person-years. The adjusted hazard ratio (HR) for all-cause mortality in all vegetarians combined versus nonvegetarians was 0.88 (95% CI, 0.80-0.97). The adjusted HR for all-cause mortality in vegans was 0.85 (95% CI, 0.73-1.01); in lacto-ovo–vegetarians, 0.91 (95% CI, 0.82-1.00); in pesco-vegetarians, 0.81 (95% CI, 0.69-0.94); and in semi-vegetarians, 0.92 (95% CI, 0.75-1.13) compared with nonvegetarians. Significant associations with vegetarian diets were detected for cardiovascular mortality, noncardiovascular noncancer mortality, renal mortality, and endocrine mortality. Associations in men were larger and more often significant than were those in women.

Conclusions:

The investigators concluded that vegetarian diets are associated with lower all-cause mortality and with some reductions in cause-specific mortality. Results appeared to be more robust in males.

Perspective:

These data suggest that vegetarian dietary patterns are associated with improved survival compared to nonvegetarian diets. It is interesting that men appeared to benefit compared to women. Further exploration of factors that may influence the association between diet and mortality among women is warranted.

Clinical Topics: Diabetes and Cardiometabolic Disease, Prevention, Diet

Keywords: Neoplasms, Protestantism, Food Habits, Diet, Vegetarian, Smoke, Cardiovascular Diseases, Energy Intake


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