Vitamin B6 (Pyridoxine)

What it does

Vitamin B6, or pyridoxine, is a versatile coenzyme involved in more than a hundred enzyme reactions, most of them concerned with protein and amino acid metabolism. It helps the body break down dietary protein, build new amino acids, and convert one amino acid into another as needs change. This makes it especially important when protein intake is high or when the body is growing or repairing tissue.

One of its most important jobs is helping to make neurotransmitters — the chemical messengers of the nervous system — including serotonin, dopamine and GABA. Through this it supports mood, sleep and normal nerve function. Vitamin B6 also helps produce haemoglobin, so it is needed for healthy red blood cells and oxygen transport, and it works alongside folate and vitamin B12 to keep levels of the amino acid homocysteine in a healthy range.

It is found in poultry, fish, potatoes, bananas, wholegrains and many other foods, so dietary deficiency is uncommon on its own. Unusually for a water-soluble vitamin, very high supplement doses taken over a long period can be harmful, causing nerve damage in the hands and feet — a reminder that "water-soluble" does not mean limitless.