A study by the Johns Hopkins University component of the Multicenter AIDS Cohort Study (MACS) followed B vitamin blood levels in 310 HIV-positive men for nine years. In a report last winter,1 the MACS investigators noted that those with abnormally low serum levels of cobalamin (B12) in their blood progressed to AIDS almost twice as fast as those with normal levels. Another study2 presented this year was a follow-up of similar observations made earlier by an HIV nutrition research group at the University of Florida. The new data documented a correlation between low vitamin B12 levels and cognitive impairment in 108 HIV-positive volunteers -- and this association increased as time passed. The particular areas where problems appeared were semantic (verbal) memory, cognitive efficiency, delayed visual recall and short-term memory.

The original Florida study of cognitive function3 was confined to persons with HIV who were relatively asymptomatic or in the early stages of the disease. It found that approximately 25% of the participants demonstrated either marginal or overt vitamin B12 deficiency. When cognition was assessed, those participants with low B12 levels performed more poorly than did those with normal vitamin B12 levels (at least 180 pmol/l). Participants were tested on information processing speed and visuospatial problem-solving skills.

These findings suggest that concurrent vitamin B12 deficiency may be a factor in cognitive changes observed in both the early and late stages of HIV infection, even when blood abnormalities are not yet apparent. Possible mechanisms whereby low B12 may cause psychoneurological symptoms involve increased oxidative stress in the brain, as signaled by the accumulation in the cerebrospinal fluid of metabolites such as methylmalonic acid and homocysteine, which are related to oxidative stress in the brain. The results emphasize the potential importance of early clinical intervention in the possible prevention of such early-onset cognitive changes.

Suggested vitamin B12 supplementation can be very high. Lark Lands, a nutrional advocate who specializes in HIV, recommends 1,000 micrograms in nasal gel or injection, administered two to seven times per week along with folic acid (5,000 to 10,000 micrograms per day).


1 Tang AM et al. Journal of Nutrition. February 1997; 127(2):345-51.

2 Posner G et al. "Nutrition and HIV Infection." April 23-25, 1997; Cannes, France (abstract O-23).

3 Beach RS et al. Archives of Neurology. May 1992; 49(5):501-6.