Vitamin Supplements

Vitamin B-6 (pyridoxine)

Vitamin B-6 (discovered in 1934) is crucial to many biological processes, including, most importantly, amino acid metabolism and biosynthesis. Vitamin B-6 is found in most foods, but meat provides the most usable form of the substance. White bread, and other grains, are often fortified with the vitamin. Vitamin B-6 deficiency is considered rare in human populations, although marginal deficiency may occur more frequently. Deficiency of vitamin B-6 produces profound skin and neurological changes, such as peripheral neuropathy. Vitamin B-6 is often co-administered with Isoniazid (a tuberculosis treatment) to reduce drug-related toxicities. Other uses of Vitamin B-6 (some of which are controversial) include: as a stimulant of hematopoiesis in patients with siderblastic anemia, as a treatment for iron-storage disease, as a treatment for schizophrenia, and as ma treatment to reduce the incidence of seizures in alcoholics.

Vitamin B-6 and Immunity

Little is known about this vitamin's role in immunity or its mechanism of action, although it appears to play a significant role. Animal studies suggest that B-6 deficiency has a range of effects on cell mediated immunity. Delayed-type hypersensitivity reactions to tuberculin antigen are decreased in guinea pigs fed a B-6 deficient diet. Lymphocyte proliferation and cytotoxicity are reduced in mice after five weeks on a B-6 deficient diet. Vitamin B-6 deficiency in animals may also lead to lymphoid organ atrophy and impaired thymic function, reduced T lymphocytes numbers and function, and defective lymphocyte maturation. Vitamin B-6 deficiency can also lead to impaired antibody production and fewer antibody-producing cells in animals, according to various studies.

Few human studies address the issue of vitamin B-6 and immunity, and those that have examined the question demonstrate no consistent direction of effect. Two studies of vitamin B6 deficiency in humans show that it may slightly impair antibody production or leave it unchanged.

Vitamin B-6 and AIDS

There has been little research directed at Vitamin B-6 and AIDS. No study has shown that Vitamin B-6 supplements delay disease progression or improve survival. One study examined Vitamin B-6 levels in a group of HIV-infected people and that 35 percent of subjects had overt deficiency and an additional 18 percent had marginal deficiency. The authors suggest that CD4 cell counts were lower in patients with reduced vitamin B-6. The authors also suggest that vitamin B-6 intake was inadequate in these subjects, based on food intake surveys. However, the diagnosis of vitamin B-6 serum levels is difficult and may be affected by the APR. Food intake surveys are also not considered a reliable method for diagnosing vitamin deficiency.

Vitamin B-6 may be reduced when tumor necrosis factor (an inflammatory cytokine) is increased, according to a study of rheumatoid arthritis patients. Furthermore, Vitamin B-6 is stored in muscle and deficiency may be related to decreased lean body weight.

Vitamin B-12 and Folate

Vitamin B-12 and folate are separate vitamins, although they have similar biological roles and work together in vivo. Folate is critical to the synthesis of RNA and DNA. The main biological effect of Vitamin B-12 is probably on folate metabolism. Folate is found in most foods, although its deficiency is common in the developed world, affecting an estimated 8 to 10 percent of the population. Vitamin B-12 is produced mainly by bacteria which live in the human gut, although it is also found in meat. Vitamin B-12 deficiency is considered rare, except in some strict vegetarians who endure 20 to 30 years of inadequate intake, suggesting there are considerable body stores of the vitamin. Most Vitamin B-12 deficiency is thought to result from altered intestinal flora and malabsorption. Folate and Vitamin B-12 deficiency result in clinically similar syndromes, producing anemia and neurologic symptoms.^[19-36]

Folate utilization can be impaired (thus producing a functional deficiency despite adequate intake) in the context of Vitamin B-12, methionine (an amino acid) or zinc deficiencies. Some drug therapy can also cause functional folate deficiency Folate deficiency can also cause neural tube defects (a birth defect in children born to mothers who consume inadequate amounts of the nutrient).