Vitamin B6
Pyridoxine
Vitamin B6 is needed for most biological reactions (i.e. amino acid metabolism, neurotransmitter synthesis, red blood cell formation). It comes in three forms: pyridoxal, pyridoxine and pyridoxamine. All of them can be converted into the coenzyme PLP (pyridoxal phosphate), which transfers amino groups from an amino acid to produce less essential amino acids, an action valuable in protein and urea metabolism. The conversion of the amino acid tryptophan to niacin or the neurotransmitter serotonin also depends on PLP. In addition, PLP is involved in the synthesis of the heme compound in hemoglobin, the nucleic acids in DNA and lecithin, a fatty compound (phospholipid) that provides structure to our cells. Vitamin B6 is stored in muscle tissue.
Main sources of vitamin B6
There are many good sources of vitamin B6, such as chicken, liver (from cattle, pigs), fish (salmon, tuna). Nuts (walnuts, peanuts), chickpeas, corn and whole grain cereals, and vegetables (especially green leafy vegetables), bananas, potatoes and other starchy vegetables are also good sources of vitamin B6.
Bioavailability of vitamin B6
With a mixed diet, the bioavailability of vitamin B6 is about 75%. Vitamin B6 is destroyed by heat, but remains stable during storage.
Risks associated with insufficient or excessive intake of vitamin B6
Vitamin B6 deficiency alone is rare; it usually occurs in combination with deficiencies of other B vitamins. Those at risk of deficiency are alcoholics and people taking anti-tuberculosis drugs. Signs of vitamin B6 deficiency include microcytic anemia due to insufficient hemoglobin synthesis, depression, nervous system problems and irritability. No side effects have been observed with high intake of vitamin B6 (from food or supplements).
