Vitamin B6 is a central molecule in the cells of living organisms. It is a water-soluble vitamin in many foods, including meat, fish, nuts, beans, grains, fruits, and vegetables. Vitamin B6 is also an ingredient in multivitamin preparations for adults and children and is added to processed foods and nutritional powders as a supplement.
Six naturally occurring active compounds of vitamin B6, known as vitamers, exist in mammals. The most common are pyridoxine, pyridoxal, and pyridoxamine. Chemically, the latter differs from the first two by an amine group and a 2,5' phosphate ester. The two most significant esters are the active coenzyme forms, pyridoxal 5'phosphate (PLP) and pyridoxamine 5'phosphate (PMP). The primary forms of vitamin B6 in meats are esters, and the dominant plant source is pyridoxine, which is less bioavailable. Pyridoxine is the usual vitamer in multivitamin supplements.
As a coenzyme, vitamin B6 is a co-factor in over 100 enzymatic reactions, including carbohydrate, amino acid, and lipid metabolism. It plays a role in gluconeogenesis and glycogenolysis. Vitamin B6 is critical in transamination and decarboxylation, the initial steps of porphyrin synthesis. Pyridoxine influences cognitive development due to its involvement in neurotransmitter synthesis and immune function because of its role in interleukin-2 (IL-2) production. It is also essential in hemoglobin synthesis.
Fetal brain development requires adequate vitamin B6, and this continues throughout infancy. The recommended daily allowance (RDA) of vitamin B6 varies with age and life stage, with pregnant and breastfeeding women requiring higher amounts than others.
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