Vitamin B₆

Vitamin B 6 is a family of related compounds comprised of pyridoxine (PN), pyridoxal (PL), and pyridoxamine (PM), along with their phosphate esters and glucosides. The primary vitamin B 6 coenzymic form, pyridoxal 5 '-phosphate, is an obligatory cofactor in over 140 enzymatic reactions primarily in the metabolism of amino acids but also in reactions of carbohydrates and lipids. Vitamin B 6 also plays a vital role in one-carbon metabolism, facilitating cellular methylation processes, methionine recycling, regulation of homocysteine, and synthesis of cysteine. Recent findings indicate that marginal vitamin B 6 status remains a concern in human nutrition, at least in segments of the population. The consequence of marginal vitamin B 6 status is unclear but serves as cause for concern in view of associations between low vitamin B 6 status, risk of cardiovascular disease and stroke, and certain cancers. This chapter provides an overview of vitamin B 6 bioavailability, metabolism and metabolic function, nutritional status and assessment, and roles in human health and disease.