Why is HIV so prevalent in Africa?

... asks Melinda Wenner. Geographer Harold Foster is convinced that it is due to low soil selenium levels. Selenium is mobile, prone to leaching as well as accumulation. Health-wise, it is one of the more interesting elements. Reputed to be an immune system stimulant, yet it is notorious for accumulating in plants and soil to a toxic degree.

Sub-Saharan Africa, with 96 percent of all AIDS cases, has a wide variety of soil types (see soil map provided) but which generally have low soil selenium.

Senegal has a significantly lower level of AIDS infection than the rest of sub-Saharan Africa. It also has uncommonly high soil selenium.

Foster's most recent article is pay walled by Elsevier, but the abstract is certainly intriguing:

The global diffusion pattern of HIV/AIDS is strongly suggestive of a protective role for the trace element selenium. It is hypothesized here that the body's antioxidant defense system, especially the selenoenzyme glutathione peroxidase, acts as an initial defense against viral infection, preceding the formation of antibodies. [emphasis added] For this reason, HIV is having its greatest difficulty in infecting those with diets elevated in amino acids and the trace element selenium which, when eaten together, stimulate the body's production of glutathione peroxidase.

One selenium link to AIDS is well established: A low selenium blood level of selenium among HIV/AIDS infected patients is associated with high AIDS-related mortality. Foster has been writing about this for some time in terms of treatment.

Since this virus encodes for glutathione peroxidase, as it replicates it deprives its host of selenium, cysteine, glutamine and tryptophan, eventually causing severe deficiencies of each in HIV-1 seropositive individuals. AIDS is the end product of these declines and the majority of its symptoms are caused by these deficiencies. Selenium and cysteine inadequacies, for example, undermine the immune system in a process that is accelerated by other infectious pathogens. A deficiency of glutamine promotes muscle wasting and digestive malfunction, while a lack of tryptophan and the compounds it biosynthesizes (such as niacin and serotonin) causes dermatitis, diarrhea and various neurologic and psychiatric symptoms including dementia. It is also clear from the literature that supplementation relieves these symptoms and would, therefore, appear to be the most logical treatment for AIDS. The major aim of this treatment would be to return body levels of selenium, cysteine, glutamine and tryptophan to normal. The evidence suggests that this would greatly reduce HIV-1's ability to replicate. Doses, therefore, would vary with the disease stage. It also is probable that niacin and serotonin would prove beneficial.

One double-blind, randomized, placebo-controlled trial has solidly confirmed the ability of 200 micrograms (μg) a day of bioavailable selenium to significantly affect viral load among AIDS patients. That is certainly good news and confirms selenium as a viable treatment.

Foster has now advanced beyond treatment into an area likely to be far more controversial: He is saying that, in low selenium soil regions, dietary selenium can reduce the risk of infection and rate of spread of the AIDS virus between individuals. The world hopes that he is correct.