<P> B vitamins are a class of water - soluble vitamins that play important roles in cell metabolism . Though these vitamins share similar names, they are chemically distinct that often coexist in the same foods . In general, dietary supplements containing all eight are referred to as a vitamin B complex . Individual B vitamin supplements are referred to by the specific number or name of each vitamin: B = thiamine, B = riboflavin, B = niacin, etc . Some are better known by name than number: niacin, pantothenic acid, biotin and folate . </P> <P> Each B vitamin is either a cofactor (generally a coenzyme) for key metabolic processes or is a precursor needed to make one . </P> <Table> <Tr> <Th> B number </Th> <Th> Name </Th> <Th> Thumbnail description </Th> </Tr> <Tr> <Td> Vitamin B </Td> <Td> thiamine </Td> <Td> A coenzyme in the catabolism of sugars and amino acids . </Td> </Tr> <Tr> <Td> Vitamin B </Td> <Td> riboflavin </Td> <Td> A precursor of cofactors called FAD and FMN, which are needed for flavoprotein enzyme reactions, including activation of other vitamins </Td> </Tr> <Tr> <Td> Vitamin B </Td> <Td> niacin (nicotinic acid), nicotinamide riboside </Td> <Td> A precursor of coenzymes called NAD and NADP, which are needed in many metabolic processes . </Td> </Tr> <Tr> <Td> Vitamin B </Td> <Td> pantothenic acid </Td> <Td> A precursor of coenzyme A and therefore needed to metabolize many molecules . </Td> </Tr> <Tr> <Td> Vitamin B </Td> <Td> pyridoxine, pyridoxal, pyridoxamine </Td> <Td> A coenzyme in many enzymatic reactions in metabolism . </Td> </Tr> <Tr> <Td> Vitamin B </Td> <Td> biotin </Td> <Td> A coenzyme for carboxylase enzymes, needed for synthesis of fatty acids and in gluconeogenesis . </Td> </Tr> <Tr> <Td> Vitamin B </Td> <Td> folate </Td> <Td> A precursor needed to make, repair, and methylate DNA; a cofactor in various reactions; especially important in aiding rapid cell division and growth, such as in infancy and pregnancy . Synthetic folate is known as folic acid . </Td> </Tr> <Tr> <Td> Vitamin B </Td> <Td> various cobalamins; commonly cyanocobalamin or methylcobalamin in vitamin supplements </Td> <Td> A coenzyme involved in the metabolism of every cell of the human body, especially affecting DNA synthesis and regulation, but also fatty acid metabolism and amino acid metabolism . </Td> </Tr> </Table> <Tr> <Th> B number </Th> <Th> Name </Th> <Th> Thumbnail description </Th> </Tr>

How many different types of vitamin b are there
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