Vegetarian diets and risk of all-cause mortality in a population-based prospective study in the United States

The popularity of vegetarian diets has increased the need for studies on long-term health outcomes. A limited number of studies, including only one study from a non-vegetarian population, investigated the risk of mortality with self-identified vegetarianism and reported inconsistent results. This study evaluated prospective associations between vegetarian diets and all-cause mortality among 117,673 participants from the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial cohort study. Vegetarian diet status was self-identified on the questionnaire. Deaths were ascertained from follow-up questionnaires and the National Death Index database. Multivariable Cox regression models were used to estimate the risk of all-cause mortality in hazard ratio (HR) and 95% confidence intervals (CI). By diet group, there were 116,894 omnivores (whose diet does not exclude animal products), 329 lacto- and/or ovo-vegetarians (whose diet excludes meat, but includes dairy and/or eggs), 310 pesco-vegetarians (whose diet excludes meat except for fish and seafood) and 140 vegans (whose diet excludes all animal products). After an average follow-up of 18 years, 39,763 participants were deceased. The risk of all-cause mortality did not statistically significantly differ among the four diet groups. Comparing with the omnivore group, the HR (95% CI) were 0.81 (0.64-1.03) for pesco-vegetarian group, 0.99 (0.80-1.22) for lacto- and/or ovo-vegetarian group and 1.27 (0.99-1.63) for vegan group, respectively. Similarly, mortality risk did not differ when comparing lacto- and/or ovo-vegetarians plus vegans with meat/fish eaters (omnivores and pesco-vegetarians) (HR [95% CI] = 1.09 [0.93-1.28]). As this study is one of the two studies of vegetarianism and mortality in non-vegetarian populations, further investigation is warranted.

Vegetarian diet and all-cause mortality: Evidence from a large population-based Australian cohort - the 45 and Up Study

The vegetarian diet is thought to have health benefits including reductions in type 2 diabetes, hypertension, and obesity. Evidence to date suggests that vegetarians tend to have lower mortality rates when compared with non-vegetarians, but most studies are not population-based and other healthy lifestyle factors may have confounded apparent protective effects. The aim of this study was to evaluate the association between categories of vegetarian diet (including complete, semi and pesco-vegetarian) and all-cause mortality in a large population-based Australian cohort. The 45 and Up Study is a cohort study of 267,180 men and women aged ≥45years in New South Wales (NSW), Australia. Vegetarian diet status was assessed by baseline questionnaire and participants were categorized into complete vegetarians, semi-vegetarians (eat meat≤once/week), pesco-vegetarians and regular meat eaters. All-cause mortality was determined by linked registry data to mid-2014. Cox proportional hazards models quantified the association between vegetarian diet and all-cause mortality adjusting for a range of potential confounding factors. Among 243,096 participants (mean age: 62.3years, 46.7% men) there were 16,836 deaths over a mean 6.1years of follow-up. Following extensive adjustment for potential confounding factors there was no significant difference in all-cause mortality for vegetarians versus non-vegetarians [HR=1.16 (95% CI 0.93-1.45)]. There was also no significant difference in mortality risk between pesco-vegetarians [HR=0.79 (95% CI 0.59-1.06)] or semi-vegetarians [HR=1.12 (95% CI 0.96-1.31)] versus regular meat eaters. We found no evidence that following a vegetarian diet, semi-vegetarian diet or a pesco-vegetarian diet has an independent protective effect on all-cause mortality.