Vitamin B6 (pyridoxine) is important in metabolism of proteins, lipids and carbohydrates. It is required for nerve and cognitive health, protects immune function and prevention of anemia.
It can be found in a wide variety of foods – beans, grains, nuts, fish, meat, vegetables, and non-citrus fruits, so it is rarely deficient in those who have a healthy diet unless they have coeliac disease or inflammatory bowel disease. It has been seen in pregnancy and pre-eclampsia, but is most commonly associated with alcohol-use disorder, tobacco smoking, protein-energy malnutrition or obesity. Absorption of vitamin B6 can be impaired in the elderly, rheumatoid arthritis, hepatitis, or kidney failure.
It is unlike any other vitamin in that deficiency or excess can cause similar symptoms, such as peripheral neuropathy.
Deficiency can cause a syndrome indistinguishable from Pellagra (which is due to Vitamin B3 / niacin deficiency). Weakness, dizziness, inflamed tongue, cheilosis, dermatitis (seborrheic, in sun-exposed areas), numbness/weakness/burning of the hands/feet, incoordination, depression, irritability, confusion or seizures can be signs of deficiency. It increases the risk of heart attack, stroke and blood clots.
Meyer HE, Willett WC, Fung TT, Holvik K, Feskanich D. Association of high intakes of vitamins B6 and B12 from food and supplements with risk of hip fracture among postmenopausal women in the Nurses’ Health Study. JAMA Netw Open. 2019 May 3. 2 (5):e193591. [QxMD MEDLINE Link].
Because of the risk of excess vitamin B6, it is best to supplement it using food choices, rather than tablets. The best sources are liver, fish, chicken, beans, peas, tomato, oranges, bananas, and avocados. Additional supplementation should be considered when using certain medications – isoniazid, hydralazine, levo-dopa and penicillamine.