Pyridoxine, or vitamin B6, is a member of the water-soluble family of B vitamins. It is necessary in the processes to metabolize proteins, fats, and carbohydrates, to make hormones and neurotransmitters, and to support the immune system. It also plays a role in the production of normal, healthy red blood cells and some of the neurotransmitters needed for proper nervous system function. In conjunction with folic acid and cobalamin, it acts to reduce homocysteine levels, thus lowering the risk of developing heart disease.
Mild deficiencies of pyridoxine are common, despite the low daily requirements. The Recommended Daily Allowance (RDA) for babies under six months of age is 0.3 milligrams (mg), and for babies six months to one year old is 0.6 mg. The daily requirement is 1.0 mg for children one to three years old, 1.1 mg for those four to six years old, and 1.4 mg for seven- to ten-year-olds. Males aged 11–14 years need 1.7 mg, and those 15 years and older need 2.0 mg. Women need slightly less; 1.4 mg for females 11–14 years, 1.5 mg for those 15–18 years, and 1.6 mg for women age 19 years and older. Requirements are somewhat increased during pregnancy (2.2 mg) and lactation (2.1 mg).
Pyridoxine has numerous therapeutic uses apart from merely treating deficiency. It has a calming effect on the nervous system, and may alleviate insomnia by increasing serotonin levels in the brain. Because of the calming effects of pyridoxine, it has been tried as a possible adjunctive treatment for schizophrenia. As of 2002, however, the findings are inconclusive. Studies of larger patient populations have been recommended.
There is good evidence that pyridoxine reduces the nausea for about a third of pregnant women who experience morning sickness. In addition, pyridoxine does not have any harmful effects on the fetus. It is also used to decrease the risk of heart disease by lowering homocysteine levels. Taken in conjunction with magnesium supplements, pyridoxine has been found to have beneficial effects on some people with autism. The vitamin B6 and magnesium combination can also help to prevent the recurrence of calcium oxalate kidney stones in susceptible people. Those who are affected by depression or gestational diabetes may benefit from a moderate addition of it, as well. One type of hereditary anemia and several metabolic diseases are effectively treated with high doses of pyridoxine. A few chemotherapeutic agents, including vincristine, can be taken with fewer side effects when pyridoxine is added to the patient's regimen. The data are equivocal on whether or not asthma is improved by vitamin B6 supplementation, but high doses—50 mg, taken twice daily—were used in the studies performed, creating a risk of nerve injury. There is some question as to the benefit to taking it for PMS, carpal tunnel syndrome, or diabetic neuropathy, although there is no harm in a trial of additional B6 at a modest level. Taking B6 has some benefit for those suffering from osteoporosis and epilepsy. Nevertheless, the advice of a health care professional should be sought before undertaking this, and any, supplemental treatment.
Judith Turner, Rebecca J. Frey PhD, The Gale Group Inc., Gale, Detroit,