Vitamin B6 is a water soluble nutrient which occurs as pyridoxine, pyridoxal, and pyridoxamine. More than 100 enzymes in the human body require the presence of vitamin B6 for protein metabolism. The synthesis of neurotransmitters such as dopamine and serotonin depend upon this vitamin. Moreover, it enables the conversion of the amino acid tryptophan to the vitamin niacin to take place.
Functions of the vitamin
The vitamin maintains the immune and nervous systems. It has the important role to make hemoglobin for the human red blood cell and to facilitate the transport of oxygen. Deficiency of vitamin B6 may therefore lead to red cell anemia. Another consequence of deficiency includes immune system compromise because of the vitamin’s role in maintenance of the spleen, thymus gland, and lymph nodes.
Though not common in the United States, deficiency of this nutrient may lead to sores of the mouth and tongue, irritability, mental confusion, and psychological depression.
Sources of vitamin B6 include whole grains, eggs, fortified breads and cereals, beans, meat, nuts, poultry, fish, fruit, and vegetables. For adult men and women ages 19 to 50, the recommended daily allowance is 1.3 milligrams. After age 51, the requirement is 1.7 milligrams for men and 1.5 milligrams for women. Adolescent girls and women need 1.9 milligrams each day during pregnancy and 2.0 milligrams while they breastfeed.
Prevention and treatment of chronic disease
Many have suggested that vitamin B6, and other nutrients of the vitamin B complex, are useful in the prevention and treatment of certain medical conditions. For example, there are publications on the use of vitamin B6 to manage carpal tunnel syndrome. Though some continue to take the vitamin for this condition, there is no scientific evidence that it is a satisfactory therapeutic agent for that.
Furthermore, the Institute of Medicine recommends that people not take more than 100 milligrams of vitamin B6 each day. There have been several cases of sensation abnormalities or neuropathy in patients who took more than 100 milligrams daily for carpal tunnel. However, discontinuation of vitamin B6 supplementation will reverse the neuropathy in these cases.
Some women have taken vitamin B6 supplementation for premenstrual syndrome, but there is no scientific evidence that symptom relief is the result of excessive doses of the vitamin. Even though vitamin B6 is a water soluble nutrient which the kidneys excrete whenever a person takes excessive doses, there is still the risk of neuropathy in women who take it for premenstrual syndrome.
Some have also suggested the use of vitamin B6 for the prevention of coronary heart disease. The reason for this idea is that deficiency of vitamin B6, folic acid, or vitamin B12 will raise blood levels of homocysteine, and high levels of homocysteine comprise a well-known risk factor for heart disease. There is, however, no current recommendation that the general public take supplements of these vitamins to prevent coronary heart disease.
Supplementation of vitamin B6 is useful in alcoholic patients who develop neuropathy. These patients tend to be deficient in several nutrients, and they will probably benefit from supplementation in conjunction with a well-balanced diet.
It is also true that isoniazid, a drug to treat tuberculosis, may lead to symptoms of vitamin B6 deficiency. In fact toxicity with this agent may result in seizures and coma, but the administration of vitamin B6 will reverse those conditions. Physicians vary in their opinions as to whether every patient who receives isoniazid should also take vitamin B6 supplementation.
Sources
- American Cancer Society. (2010). Vitamin B complex. Retrieved March 1, 2011.
- National Institutes of Health. Office of Dietary Supplements. (2007). Dietary Supplement Fact Sheet: Vitamin B6. Retrieved March 1, 2011.
Michael Koger - Dr. Koger obtained his medical education at Meharry Medical College and specialized in Internal Medicine.
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