Vegetarian Diets May Not Outperform Flexitarian Eating for Longevity

The question of whether dietary choices can meaningfully extend human lifespan is central to longevity research, and vegetarian diets have long been championed as a path to longer life. This 2025 narrative review, published in Maturitas, takes a critical look at that assumption — and finds it surprisingly unsupported by robust evidence.

The authors reviewed existing literature on vegetarianism and multiple longevity-related outcomes, including gut microbiome health, body weight, cardiovascular risk, systemic inflammation, telomere length, and all-cause mortality. While vegetarianism is widely adopted for ethical, environmental, and religious reasons and is popularly associated with health benefits, the synthesis of current evidence tells a more complicated story.

Key findings challenge several assumptions. Studies reporting lower mortality rates among vegetarians compared to meat-eaters were found to be highly biased — likely reflecting the 'healthy user' effect, where vegetarians also tend to exercise more, avoid smoking, and engage in other health-promoting behaviors. Evidence linking vegetarian diets to improved telomere length, a biological marker of cellular aging, was deemed insufficient and of low quality.

The review also examined blue zones — geographic regions with disproportionately high numbers of centenarians. Critically, only one of the recognized blue zones (Loma Linda, California) is predominantly vegetarian. The others, including Sardinia, Okinawa, Ikaria, and the Nicoya Peninsula, are largely inhabited by flexitarians who consume modest but regular amounts of animal products.

The authors conclude that the available evidence does not support vegetarian diets as superior to flexitarian diets for promoting longevity. They emphasize that this remains an open scientific question requiring more rigorous, well-controlled research before firm dietary recommendations can be made.