Vitamin B6, also known as pyridoxine, is one of eight water-soluble B vitamins. Pyridoxine plays a major role in protein metabolism – that is, the conversion of proteins to energy. Pyridoxine is also involved in cognitive development, or brain function, via the development of neurotransmitters.
Foods highest in pyridoxine include fish, organ meats (liver, heart, kidney, etc.), potatoes and other starchy vegetables, and non-citrus fruits. In the United States, and most of the developed world, young people and adults get the bulk of their vitamin B6 from fortified cereals, meat, poultry, potatoes, and some non-citrus fruits.
People in the developed world rarely encounter pyridoxine deficiencies. Where these do occur, it is usually among individuals who have reduced kidney function, intestinal malabsorption defects like Crohn’s disease, celiac disease and ulcerative colitis, and people with autoimmune disorders like rheumatoid arthritis.
People with alcohol dependence may also be deficient in vitamin B6, largely because the acetaldehyde competes with other cells to “capture” vitamin B6, and then discards it via the kidneys before it is used.
The symptoms of pyridoxine deficiency include anemia, brain scan (electroencephalographic) abnormalities, rough, scaly skin, cracks at the corners of the mouth, and glossitis – a swollen, reddened tongue. Major vitamin B6 (pyridoxine) deficiencies can cause depression and confusion, chronic inflammation, and a weakened immune system.
Pyridoxine supplements are available as part of a multivitamin regimen, as part of a vitamin B-complex tablet or gel cap, sublingually (i.e. under the tongue), and as a standalone pyridoxine supplement, often labeled pyridoxine hydrochloride, or HCL.
About 28 to 36 percent of the general population in the U.S. uses vitamin pyridoxine supplements, in one form or another. The two largest vitamin B6 user groups are those aged 51 and older, and those younger than nine. The recommended daily values for vitamin B6 are 0.3 to 0.5 milligrams (mg) under eight years; 1 to 1.3 mg from nine to 50 years; and 1.7 for those over 51. Upper limit levels for the same groups are 40 mg and 100 mg.
According to one study, low levels of pyridoxine may contribute to the chronic inflammation that marks not only heart disease but also other common conditions.