Several observational studies point toward a longer life with a healthy, predominantly plant-based eating pattern. That advantage, however, appears to stem mainly from the quality of the diet rather than from the strict label of 'vegetarian' or 'vegan'. The evidence is purely associational, and for vulnerable groups such as older adults and pregnant women a strict plant-based diet carries real risks of nutritional deficiencies.
A healthy plant-based diet has been associated with a lower risk of premature death in several observational studies. Older Chinese adults who ate the most fresh plant foods, such as fresh fruit, vegetables, legumes, nuts and tea, were 19% less likely to die than those who ate the least plant-based food1. Vegetarians also show a lower risk of cardiovascular mortality in multiple studies, probably through lower cholesterol levels, a healthier body weight and a higher antioxidant intake2,3. The Mediterranean diet, which is not vegetarian but does contain many plant-based components, has been consistently linked to longer survival in several European studies4,5.
Yet the picture is more nuanced than 'plant-based is always better'. When vegetarians are compared with health-conscious non-vegetarians, people who also pay attention to their lifestyle but occasionally eat meat, the difference in mortality from most cancers and stroke disappears2. This suggests that a healthy lifestyle in general carries more weight than the elimination of meat per se. A recent review study also finds no clear advantage of a fully vegetarian diet over a flexitarian diet; of the well-known regions with a notably high proportion of centenarians, only one has a population that eats predominantly vegetarian6.
The quality of plant-based food turns out to be the decisive factor, not the quantity. A plant-based diet high in preserved vegetables and sugar was actually linked to 17% higher mortality1. Fresh and unprocessed plant foods are protective; processed and sweetened plant foods are not. This distinction is practically more important than the question of whether someone calls themselves a 'vegetarian'.
In vegans, the overall mortality rate in available studies is comparable to that of vegetarians and people who occasionally eat meat; a proven advantage for a longer lifespan has therefore not been established7. In one specific group, adults over eighty in China, a vegetarian or vegan diet was even linked to a lower likelihood of reaching one hundred years of age, particularly in people who were underweight8. The researchers conclude that at an advanced age a varied diet containing both animal and plant foods may be better for exceptional longevity.
For certain groups, a strict vegan diet carries concrete risks. Deficiencies in vitamin B12, vitamin D, omega-3 fatty acids, iron, calcium and zinc have been documented in children, pregnant women and older adults following a vegan diet. Supplementation is necessary for these groups7,8,3. This is not a reason to avoid plant-based eating, but it is a reason to pay close attention to it.
All studies are observational (cohort or review studies); causal conclusions cannot be drawn. Populations vary widely (China, Europe, North America). No randomised trials are available for the endpoint of mortality.