B6

B6, in nutrition literature, refers to vitamin B6, a water-soluble vitamin that encompasses several chemically related compounds, including pyridoxine, pyridoxal, and pyridoxamine. In humans, pyridoxal 5'-phosphate (PLP) and pyridoxamine 5'-phosphate (PMP) are the active coenzymes in many processes.

In metabolism, PLP acts as a coenzyme for a wide range of enzymatic reactions, especially in amino acid metabolism such as transamination, decarboxylation, and racemization. It also contributes to glycogenolysis through glycogen phosphorylase, and is essential for the synthesis of neurotransmitters (such as serotonin, dopamine, and gamma-aminobutyric acid), heme production, and the metabolism of sphingolipids. B6 is also involved in immune function and the maintenance of normal brain development and function.

Dietary sources of vitamin B6 include poultry, fish, beef, potatoes, bananas, chickpeas, and fortified cereals and other fortified foods. It is available as a stand-alone supplement and as part of multivitamin formulations. The recommended daily amount for adults varies with age and sex, but is typically around 1.3 to 2.0 mg per day. Most individuals obtain sufficient B6 from a balanced diet.

Deficiency is relatively rare in developed countries but can occur with poor intake, certain medical conditions, or chronic alcohol use. Symptoms may include irritability, depression, confusion, dermatitis, glossitis, and in severe cases microcytic anemia due to impaired heme synthesis. Excessive intake of B6 from supplements can cause neuropathy, so intake should remain within established upper limits.