Brewer's yeast contains all the essential amino acids, 14 minerals, and 17 vitamins. It is one of the best natural sources of the B-complex vitamins thiamin, riboflavin, niacin, B6, pantothenic acid, biotin, and folic acid. It is also high in minerals, including chromium, zinc, iron, phosphorus, and selenium. Brewer's yeast is also a good source of protein. It contains approximately 16 g of protein per 30 g of powdered yeast.