Vitamin B12

What is it?

Vitamin B₁₂ or cobalamin is an essential nutrient found in meat products. Vitamin B₁₂ is absorbed in the small intestine and is necessary for proper nerve function and converting food into energy. Deficiencies of vitamin B₁₂ cause anemia and neurological impairments including memory loss and disorientation.

What do people with HIV use this supplement for?

To avoid deficiency
Depending on the way vitamin B₁₂ levels are measured, studies suggest that between ten and 50 per cent of people living with HIV are deficient in this nutrient. This deficiency is most likely due to HIV-related damage to the small intestine that prevents the body from absorbing adequate amounts of B₁₂. Certain drugs, such as AZT and the antibiotics used to treat tuberculosis, can decrease levels of vitamin B₁₂. Several studies suggest that deficiency in this vitamin increases the rate at which a person becomes ill (disease progression). In a study conducted by Dr. Alice Tang and colleagues, serum levels of vitamin B₁₂ were measured in HIV-positive people without symptoms of disease. Even when factors such as CD4+ counts were considered, the team found that serum vitamin B₁₂ levels could be used to predict which subjects would become ill most quickly.

B₁₂ deficiency seems to be linked to poor absorption; most nutritionists suggest therefore that supplements of B₁₂ be injected or taken sublingually (dissolved under the tongue). Although these methods have been shown to increase serum levels of B₁₂ in HIV-positive people, no trials have been done to assess the impact of B₁₂ supplements on disease progression.

To prevent and treat dementia
Given that B₁₂ deficiencies are associated with confusion and memory, many physicians and researchers have speculated that vitamin B₁₂ might play a role in dementia and other HIV-related cognitive disorders. One case report described the dramatic recovery of a HIV-positive man suffering from dementia who was treated with B₁₂. Clinical trials have produced less impressive results and it is now generally accepted that B₁₂ may be a factor in some but not all cases of HIV-related dementia. B₁₂ supplements have also been useful in treating elderly people with B₁₂ deficiencies who showed signs of memory loss and senility.

To treat peripheral neuropathy
Peripheral neuropathy is a tingling or burning in the hands and feet. It is often associated with anti-HIV drugs, particularly ddC, ddI and d4T. One early study suggested that people with HIV who have low B₁₂ levels were more likely to experience neuropathy, but subsequent studies have not confirmed this connection. B₁₂ has, however, been used successfully to treat diabetic neuropathy, a fact that argues its case for the management of nerve damage in people with HIV.

Available forms and usage

In Canada, B₁₂ is taken orally or by intramuscular or intravenous injections. Although other forms of B₁₂ have been developed, such as nasal sprays, gels and sublingual tablets, not all of these formulations are widely available in Canada. Given that vitamin B₁₂ may be poorly absorbed in HIV-positive people, most nutritionists and physicians recommend B₁₂ shots. These shots can be taken at a doctor’s office or an HIV clinic and, in most cases, they are covered by provincial and private insurance plans. A monthly injection can be used to boost a daily oral dose of B_12. If obvious signs of B₁₂ deficiency are present, more frequent injections are possible (up to several times a week). Oral doses of 25 or 50 mg of B₁₂ are found in B25 or B50 vitamin tablets respectively. These B-complex combination vitamins are described further in CATIE’s supplement sheet on vitamin B-complex.

Cautions and concerns

Vitamin B₁₂ supplements are safe to use. Excess amounts of the vitamin are eliminated in the urine. At high doses, however, B₁₂ may cause anxiety in some people and mild diarrhea in others. Some people are sensitive to B₁₂ and may develop a skin rash while taking this supplement. Since B-vitamins tend to work best together, it’s important to maintain the balance of Vitamin B₁₂ and another B-vitamin called folate (folic acid) in the body. Taking large doses of one B-vitamin alone is not a good idea so if you are taking extra B₁₂, you might want to take a B-complex pill as well.

References

Canadian Pharmaceutical Society. CPS 1999;1943-4.

Herzlich BC, Schiano TD. Reversal of apparent AIDS dementia complex following treatment with vitamin B12. Journal of Internal Medicine 1993;233:496-7.

Kieburtz KD, Giang DW, et al. Abnormal vitamin B12 metabolism in human immunodeficiency virus infection. Association with neurological dysfunction. Archives of Neurology 1991 Mar;48(3):312-4

Markle HV. Cobalamin. Critical Reviews in Clinical Laboratory Sciences 1996;33(4):247-356.

Paltiel O, Falutz J, et al. Clinical correlates of subnormal vitamin B12 levels in patients infected with the human immunodeficiency virus. American Journal of Hematology 1995 Aug;49(4):318-22

Robertson KR, Stern RA et al. Vitamin B12 deficiency and nervous system disease in HIV infection. Archives of Neurology 1993 Aug;50(8):807-11

Semba RD, Tang AM . Micronutrients and the pathogenesis of human immunodeficiency virus infection. British Journal of Nutrition 1999 Mar;81(3):181-9

Shor Posner G; Campa A et al. Increased cobalamin levels are associated with better cognitive function in HIV-1 disease, Abstract 42359. International AIDS Conference, Geneva, 1998.

Tang AM, Graham NMH et al. Low serum vitamin B-12 concentrations are associated with faster human immunodeficiency virus type 1 (HIV-1) disease progression. Journal of Nutrition 1997;127:345-51.

Trimble KC, Goggins MG. Vitamin B12 deficiency is not a cause of HIV-associated neuropathy. AIDS 1993;7(8):1132-3.