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Vitamin B6 (pyridoxine) |
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| Vitamin B6, also called pyridoxine, is one of eight water-soluble B vitamins. Vitamin B6 (pyridoxine) serves as coenzyme and is involved in the metabolism of protein and carbohydrates, the production of insulin and red and white blood cells, and the synthesis of neurotransmitters, enzymes, and prostaglandins. Vitamin B6 is essential in numerous biochemical pathways
involving red blood cells, the immune system, central nervous system function, protein metabolism, homocysteine metabolism, and also the production of energy. Pyridoxine is an especially important vitamin for maintaining healthy nerve and muscle cells and it aids in the production of DNA and RNA, the body's genetic material. It is necessary for proper absorption of vitamin B12 and for the production of red blood cells and cells of the immune system.
More specifically, vitamin B6 consists of six specific compounds, namely pyridoxine, pyridoxal, pyridoxamine, and their respective phosphates, the latter group of which are the most active components in numerous reactions involving amino acid and protein metabolism. There are six forms of vitamin B6: pyridoxal (PL), pyridoxine (PN), pyridoxamine (PM), and their phosphate derivatives: pyridoxal 5'-phosphate (PLP), pyridoxine 5'-phosphate (PNP), and pridoxamine 5'-phospate (PNP). PLP is the active coenzyme form, and has the most importance in human metabolism. In the body, pyridoxine is found primarily in the liver and muscles. Pyridoxine is utilized by the liver to synthesize pyridoxal phosphate (PLP), the active coenzyme form. PLP functions as transamination and decarboxylation coenzymes, which are involved in amino acid and protein metabolism. PLP is also involved as a coenzyme in the synthesis of heme, niacin and serotonin. Alcohol impairs vitamin B6 metabolism in the body.
The major forms of vitamin B6 from animal products are pryridoxal 5'-phosphate and pyridoxamine 5'-phosphate. The major forms of vitamin B6 from plant-derived foods are pyridoxine, pyridoxine 5'-phosphate and pyridoxine glucosides. Pyridoxine hydrochloride is the principal form of vitamin B6 used for food fortification and in nutritional supplements. Pyridoxal 5'-phosphate is also available as a nutritional supplement. Pyridoxal 5'-phosphate, is involved in a wide range of biochemical reactions, including the metabolism of amino acids and glycogen, the synthesis of nucleic acids, hemogloblin, sphingomyelin and other sphingolipids, and the synthesis of the neurotransmitters serotonin, dopamine, norepinephrine and gamma-aminobutyric acid (GABA). |
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Vitamin B6 (pyridoxine) functions, uses, and health benefits |
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| Vitamin B6 supports more vital bodily functions than any other vitamin. Vitamin B6 is a coenzyme for several enzyme systems.
Vitamin B6, used mainly in the body for the processing of amino acids, performs this task along with certain enzymes. It is vital in the metabolism of amino acids in the intestines. It allows the amino acids to be synthesized, broken down and absorbed. The forming of histamine, serotonin, dopamine and adrenaline are dependent on vitamin B6. Vitamin B6 is required for the production of serotonin and helps to maintain healthy immune system functions, to protect the heart from cholesterol deposits, and to prevent kidney stone formation.
Vitamin B6 is indicated for the treatment of sideroblast anemia, neurologic disturbances, seborrhoeic dermatitis, and cheilosis. In combination with folic acid and vitamin B12, vitamin B6 lowers homocysteine levels which is an amino acid linked to heart disease and stroke, and possibly other diseases as well, such as osteoporosis, and Alzheimer's disease. Pyridoxine is required for the balancing of hormonal changes in women as well as assisting the immune system and the growth of new cells. Vitamin B6 may be helpful in some women with premenstrual dysphoric disorder, also known as premenstrual syndrome (PMS), and may be useful in some cases of gestational diabetes and for protection against metabolic imbalances associated with the use of some oral contraceptives. Vitamin B6 promotes iron excretion and this has been used as a rationale for treatment in iron storage diseases. |
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Vitamin B6 (pyridoxine) dosage, intake, recommended daily allowance (RDA) |
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| The recommended sietary allowance (RDA) is the average daily dietary intake level that is sufficient to meet the nutrient requirements of nearly all (97 to 98%) healthy individuals in each life-stage and gender group. The most common supplemental intake is 10–25 mg per day. However, high amounts (100–200 mg per day or even more) may be recommended for certain conditions. The recommended dietary allowance (RDA) for vitamin B6 is 2.0 mg/day for the adult man and 1.6 mg/day for the adult woman. Pregnant women require an additional 0.1 mg per day and those that are lactating require and additional 0.7-0.8 mg daily. Those who use pyridoxine for the management of premenstrual syndrome, typically use doses ranging from 50 to 100 milligrams/day. Those who use pyridoxine for the management of carpal tunnel syndrome, typically use doses ranging from 100 to 200 milligrams/day. Vitamin supplements should always be taken with water, preferably after a meal. Vitamin B6 is available in nutritional supplements principally in the form of pyridoxine hydrochloride. Pyridoxal 5'-phosphate is also available as a nutritional supplement. Pyridoxine hydrochloride is available in multivitamin and multivitamin/multimineral products as well as products that, in addition to vitamins and minerals, contain other nutritional substances. Single ingredient pyridoxine products are also available. |
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Sources of vitamin B6 (pyridoxine) |
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| Sources of pyridoxine are whole (but not enriched) grains, bread, liver, cereals, spinach, green beans, and bananas. Vitamin B6 (pyridoxine) is contained in some amounts in all foods. Foods that contain the highest amounts are brewer's yeast, carrots, chicken, eggs, fish, meat, peas, spinach, sunflower seeds, walnuts, and wheat germ. Pyridoxine is needed in proportion to the amount of protein consumed. Foods rich in vitamin B6 include white meat (poultry and fish), bananas, liver, whole-grain breads and cereals, soyabeans and vegetables. Vitamin B6 is sensitive to ultraviolet light and heat, so large amounts of this nutrient are lost during the cooking process. |
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Vitamin B6 (pyridoxine) deficiency |
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| Vitamin B6 deficiency is rare, since most foods eaten contain the vitamin. Vitamin B6 deficiency is usually associated with poor absorption of nutrients in the gastrointestinal tract (as in alcoholism, or with chronic diarrhea), the taking of certain drugs (as isoniazid, hydrolazine, penicillamine) that inactivate the vitamin, with genetic disorders that inhibit metabolism of the vitamin, or in cases of starvation. Deficiency symptoms include itchy, peeling skin (dermatitis), cracked and sore lips, inflamed tongue and mouth (skin disorders similar to vitamin B2 and vitamin B3 deficiencies), neuropathy, poor coordination, confusion, and insomnia. Some of these symptoms can also result from a variety of medical conditions other than vitamin B6 deficiency. |
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Vitamin B6 (pyridoxine) overdose, toxicity, side effects |
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| Vitamin B6 is usually safe, at intakes up to 200 mg per day in adults. However, vitamin B6 can cause neurological disorders, such as loss of sensation in legs and imbalance, when taken in high doses (200 mg or more per day) over a long period of time. Vitamin B6 toxicity can damage sensory nerves, leading to numbness in the hands and feet as well as difficulty walking. Symptoms of a pyridoxine overdose may include poor coordination, staggering, numbness, decreased sensation to touch, temperature, and vibration,; and tiredness for up to six months. |
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