Science is filled with bias, and this is why I am not sure that a vegan diet is optimal or more healthy than an omnivore diet with small amounts of meat. There are many peer reviewed studies showing that higher intakes of non-animal food such as vegetables and fruit will increase longevity, but this does not mean that a diet without any meat is optimal.
Regardless, based on the totality of what I’ve read, a vegan diet looks safe and healthy (it is approved by the American Dietetic Association) and I choose to go vegan because of morality and because I have not seen any evidence to convince me that a vegan diet is unhealthy.
Many point to populations such as the Okinawans in Japan who have legendary longevity but who eat small amounts of fish. While it is true that the traditional Okinawan diet had small amounts of fish (one teaspoon per day), this does not prove that we should eat fish today because our oceans today are polluted with heavy metals, microplastics, and other toxic chemicals. Our oceans were less polluted in the past.