In a few recent scientific publications, the authors examined the differences in incidence of age-related disease and mortality in populations with differing levels of plant versus animal dietary protein intake. The closer to a vegan diet one approaches, the lower the risk of disease and mortality. There is already plenty of evidence for this outcome in the literature, although, as in all such things, the outstanding questions revolve around which of the possible mechanisms are the important ones.
For example, it should be expected that a lesser intake of animal protein will lower inflammation throughout the body. But does this effect really matter in comparison to the physiological response to the lower intake of calories one sees in people who adopt plant-based diets? Given the strength of the effects of calorie intake on long-term health, it is a very reasonable to make the argument that the bulk of the benefits of a vegan diet arise because of a lower calorie intake. Fewer calories means less visceral fat, greater operation of stress response mechanisms such as autophagy, and so forth. This adds up over the years.
Researchers reviewed clinical trials and epidemiological studies related to aging and found that while aging increases the risk for noncommunicable chronic diseases, healthful diets can help. The authors cite studies showing that plant-based diets rich in fruits, vegetables, grains, and legumes: reduce the risk of developing metabolic syndrome and type 2 diabetes by about 50%; reduce the risk of coronary heart disease events by an estimated 40%; reduce the risk of cerebral vascular disease events by 29%; reduce the risk of developing Alzheimer's disease by more than 50%.
In this analysis of a large prospective cohort of 416,104 men and women in the US with 16 years of observation, we found higher plant protein intake was associated with reduced risk of overall mortality, with men and women experiencing (respectively) 12% and 14% lower mortality per 10 g/1000 kcal intake increment (5% lower mortality per standard deviation increment). The inverse association was apparent for cardiovascular disease and stroke mortality in both sexes, was independent of several risk factors, and was evident in most other cohort subgroups.
Replacement of 3% energy from various animal protein sources with plant protein was associated with 10% decreased overall mortality in both sexes. Of note, substitution analyses suggested that replacement of egg protein and red meat protein with plant protein resulted in the most prominent protective associations for overall mortality, representing 24% and 21% lower risk for men and women, respectively, for egg protein replacement, and 13% and 15% lower risk for men and women for red meat protein replacement. The effect sizes of these risk estimates were small.