The other nine are water-soluble: C (ascorbic acid) and the eight substances grouped together in what’s called the B complex—B1 (thiamin), B2 (riboflavin), B3 (niacin), B5 (pantothenic acid), B6 (pyridoxine), B7 (biotin, also sometimes referred to as vitamin H), B9 (folate/folic acid), and B12 (cobalamin). Sometimes choline is counted as a fourteenth vitamin, but usually the roster ends at thirteen.