B vitamins are a class of water-soluble vitamins that play important roles in cellmetabolism and synthesis of red blood cells. They are a chemically diverse class of compounds, but are associated in diet, often occurring together in the same foods. Dietary supplements containing all eight are referred to as a vitamin B complex. Individual B vitamins are referred to by B-number or by chemical name, such as B1 for thiamine, B2 for riboflavin, and B3 for niacin, while some are more commonly recognized by name than by number, such as pantothenic acid (B5), biotin (B7), and folate (B9).