Vitamin B6

The principal role of vitamin B6 is to supply the body with the active form of the vitamin, pyridoxal-5′-phosphate (PLP) which acts as the cofactor for over 70 enzyme-catalyzed reactions in pathways of amino acid metabolism, folate and 1-carbon metabolism, polyamine and protein synthesis, carbohydrate and lipid metabolism, mitochondrial function and erythropoiesis. Other less well understood roles of vitamin B6 include acting as an antioxidant, modulating the activity of steroid hormone receptors and transcription factors, antagonizing the action of adenosine-5′-triphosphate (ATP) at P2 purinergic receptors and modulating immune function. Dietary vitamin B6 deficiency in infancy causes epileptic seizures. Inborn errors of metabolism leading to low PLP levels cause seizures and movement disorders in infants and peripheral neuropathy in older children/adults. Paradoxically, high doses of pyridoxine also cause peripheral neuropathy. An imbalance of B6 may also contribute to complex multifactorial diseases including hyperhomocystinemia and hence the risk of vascular disease and to the development of cancers.