Abstract
Further studies were made on the problem offered by us why the availability of B vitamins differs between animal and vegetable diets. Experiments were performed on adult subjects and rats, and it was confirmed that dietary components, especially cellulose and protein, played an important role in this problem. 1) Thiamine in urine and feces increased when cellulose was added to the diet, suggesting that thiamine synthesis by intestinal flora was accelerated. 2) On the other hand, the urinary excretion of riboflavin increased only by adding both cellulose and protein. 3) Vitamin B_<12> or methionine and tryptophan were effective remarkably.
