As I believe all humans are genetically equal in biological functions(save for male/female differences) then all can thrive on a decent vegetarian diet. The upper castes of India such as the Brahmans and also the Hare Krishnas are predominantly vegetarian and they include dairy products, and honey in their diet. Also strange how some ancient europeans such as Pathagoras himself a vegetarian believed that the ruling elite should only be vegetarians.
Naturally fermented foods such as saurkraut are easy to make and have their own healthy bacteria. Different types of fermented drinks are also popular throughout the world. Fresh eaten wild picked foods also have natural healthy organisms that the body can use.
Fermented foods take much more work than refrigeration and the world has rapidly advanced toward referigeration and slowly losing natural food preservation knowlegde.