Vitamin B6 (pyridoxine)

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).

Vitamin B6 (pyridoxine) functions, uses, and health benefits

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.

Vitamin B6 (pyridoxine) dosage, intake, recommended daily allowance (RDA)

The recommended dietary 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 1.3 mg/day for adults aged 19 to 50. 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.

Sources of vitamin B6 (pyridoxine)

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.

Vitamin B6 (pyridoxine) is found in a wide variety of foods including fortified cereals, beans, meat, poultry, fish, and some fruits and vegetables. Common natural sources of pyridoxine include bananas, carrots, nuts, rice, fish, soybeans, and wheat germ.

Symptoms of pyridoxine deficiency are very non-specific and hard to reproduce. The best sources of vitamin B6 are meats, particularly organ meats, such as liver, and the whole grains, especially wheat. Wheat germ is one of the richest sources. Besides meat, good protein sources of B6 include fish, poultry, egg yolk, soybeans and other dried beans, peanuts, and walnuts. Vegetable and fruit sources include bananas, prunes, potatoes, cauliflower, cabbage, and avocados. As examples of how easily vitamin B6 is lost in the processing of food, raw sugar cane has a good amount, while refined sugar has none; whole wheat flour contains nearly 0.5 mg. of pyridoxine (wheat germ and wheat flakes have much more), while refined wheat flour has almost none, and even whole wheat bread has lost nearly all of its vitamin B6.

Herbs that contain vitamin B6 (pyridoxine) include alfalfa, catnip, and oat straw.

Vitamin B6 can be found in multivitamins (including children's chewable and liquid drops), B complex vitamins, or can be sold individually. It is available in a variety of forms including tablets, softgels, and lozenges. Vitamin B6 is also sold under the names pyridoxal, pyridoxamine, pyridoxine hydrochloride, and pyridoxal-5-phosphate. Vitamin B6 is easily destroyed in processing of foods. More than half of the vitamin may be lost with use of the flash-frozen method for freezing fruits and vegetables, during milling of grains, and production of processed meats.

Vitamin B6 is not included as part of the enrichment mixture that is added to processed grains to compensate for milling losses so whole grains are a richer source of the vitamin. Fresh meats and raw produce also provide greater levels of Vitamin B6 than their processed counterparts.

Vitamin B6 (pyridoxine) deficiency

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.

Vitamin B6 deficiency is rare, since most foods eaten contain the vitamin. Vitamin B6, used mainly in the body for the processing of amino acids, performs this task along with certain enzymes. The enzyme that participates in this type of complex is aminotransferase. Several types of aminotransferase exist. Pyridoxine is a water soluble vitamin that is instrumental in more than 100 enzyme reactions in the body. Vitamin B6 is used by the body as a catalyst in reactions that involve amino acids.

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. Vitamin B6 deficiency is one of the most common nutritional deficiencies. Much of this is due to the fact that a lot of vitamin B6 is lost during cooking and food processing. Adequate pyridoxine is important because it is involved in the production of hemoglobin in red blood cells and neurotransmitters like serotonin, which plays a part in regulating our moods and preventing depression.

Vitamin B6 (pyridoxine) deficiency is common among people over age 65. Vitamin B6 deficiency can occur in individuals with poor quality diets that are deficient in many nutrients. With vitamin B6 deficiency, while aminotransferase continues to occur in the various organs of the body, there is an abnormally low level of the active vitamin B6/aminotransferase complex present. Thus, this vitamin deficiency results in the impairment of a variety of activities in the body. With supplement correction of the vitamin B6 deficiency, the aminotransferase then readily forms the active complex, and normal metabolism is restored. Like vitamin B1, vitamin B6 deficiency is most commonly seen in alcoholics where most of their caloric intake is obtained through alcohol. Certain drugs like isoniazid and penicillamine bind pyridoxine resulting in deficiency.

Some doctors believe that most diets do not provide optimal amounts of this vitamin. People with kidney failure have an increased risk of vitamin B6 deficiency. Vitamin B6 has also been reported to be deficient in some people with chronic fatigue syndrome. The deficiency occurred in infants fed early versions of commercial canned infant formula, when the vitamin had been inadvertently omitted from the formula. This error resulted in infants failing to grow, in irritability, and in seizures.