Vegetarian diets for longevity: friend or foe?

Vegetarianism is a healthy dietary pattern that is postulated to increase longevity. Vegetarianism is adopted for animal ethics, environmental reasons, or religious beliefs. Vegetarian diets are believed to improve the gut microbiome, body weight, cardiovascular health and inflammation; however, a synthesis of the up-to-date evidence does not seem to support these effects. When objective measures are sought, it becomes apparent that there is a lack of high-quality evidence regarding the effect of vegetarian diets on telomere length. Moreover, studies indicating lower mortality rates for vegetarians than for meat eaters appear to be highly biased. Among the geographical areas with higher-than-expected numbers of centenarians ('blue zones'), only one site is largely inhabited by vegetarians, whereas the rest have populations largely of flexitarians. Overall, available research does not indicate the superiority of vegetarian diets over flexitarian ones. The issue merits further research to help us understand vegetarianism's effects on longevity.