This is a interesting study of two geographically near tribes of people eating a plant based diet vs a animal based diet.

This type of reporting is rare, since the western diet has changed every group of humans it has contacted.

https://doi.org/10.1001/jama.1931.02730200061030

Full text: https://babel.hathitrust.org/cgi/pt?id=coo.31924003510108

This is a contribution to knowledge concerning the relation of diet to physique and to health. The two tribes selected for this investigation were chosen because of the fact that, although their territories were adjoining, their dietary customs were different, "the Akikuyu being almost exclusively vegetarian and the Masai chiefly carnivorous." The field work in this investigation covered such categories as chemical analysis of all foods in common use, articles of diet in the raw state, cooked foods, edible earths, physical examination of both adults and children, and clinical observations. Additional features of this study pertain to laboratory and hospital work dealing with the adequacy of hospital and prison diets, the effect of additions to the diet of various seemingly desirable supplements, feeding tests with prescribed diets on four groups each of forty boys, and blood studies dealing particularly with calcium and phosphorus content, sugar tolerance, ph and alkali reserve,