10 June 2010

Fungus-tainted corn spreading HIV?

A new study raises the question of whether corn contaminated with a fungus-derived toxin is helping to facilitate the transmission of HIV in sub-Saharan Africa.


A new study raises the question of whether corn contaminated with a fungus-derived toxin is helping to facilitate the transmission of HIV in sub-Saharan Africa.

The toxins, called fumonisins, are produced by a particular type of fungus that can grow in corn after the plant is damaged by pests such as the cornstalk borer.

Fumonisins may be harmful to human health, with some studies linking consumption of the toxins to an increased rate of cancer of the esophagus, the tube that connects the throat to the stomach.

In the new study, published in the American Journal of Clinical Nutrition, researchers looked at whether there may be a relationship between HIV transmission in sub-Saharan Africa and general consumption of foods prone to contamination with fumonisins or other fungus- produced toxins (known as mycotoxins).

Using data from the World Health Organisation and the Food and Agriculture Organization, the researchers found that as sub-Saharan countries' per-person corn consumption rose, so did HIV transmission rates.

What the researchers found

In countries with a relatively higher percentage of Muslims - a factor linked to lower HIV rates - those with high per-capita corn consumption had an estimated HIV infection rate of 291 per 100,000 people in one year. In contrast, the rate in those with low corn consumption was 74 per 100 000 people.

Meanwhile, in countries with both fewer Muslims than average and higher-than-average corn consumption, there were 435 HIV cases per 100 000 people.

The researchers also found that higher per-capita corn consumption correlated with a higher rate of esophageal cancer. Since fumonisin toxins have been linked to that cancer, the finding serves as an indicator that populations with high corn consumption were exposed to higher levels of the toxin.

What all of this means is not yet clear. This appears to be the first study to find an association between corn consumption and HIV transmission rates in sub-Saharan Africa, said lead researcher Dr Jonathan H. Williams, of the University of Georgia in Griffin.

More research needed

The findings, he and his colleagues say, must be considered preliminary and need to be backed up by further research.

It is biologically plausible that high fumonisin intake could make a person more vulnerable to HIV infection. According to Williams, research suggests that the toxin makes certain tissues more vulnerable to infections by viruses.

A number of factors have been identified as key in sub-Saharan Africa's HIV transmission rates; male circumcision, for example, has been shown to lower heterosexual transmission, while having multiple concurrent sex partners or other sexually transmitted infections increases the risk.

The current findings raise the possibility that food safety -- in particular, the issue of fumonisin-contaminated corn -- is an additional factor.

Based on their statistical model, Williams and his colleagues estimate that if the "maize (corn) factor" were eliminated in sub-Saharan Africa, HIV transmissions could be cut by as much as 58%.

Contamination might be prevented, for instance, by planting corn varieties genetically modified to be resistant to pests. It may also be possible to remove contaminants, Williams said, through certain milling technologies or by soaking the grain in water; fumonisin is water-soluble, so "steeping" the grain or meal, then discarding the liquid may remove the toxin.

In a region where an estimated 1.7 million people become infected with HIV annually, that would mean more than 1 million infections averted each year, the researchers note.

All of that, however, remains speculation until further research is done confirming the link between contaminated corn and HIV. - (Reuters Health, June 2010)


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Dr Sindisiwe van Zyl qualified at the University of Pretoria before working for an HIV/AIDS NPO in Soweto for many years. She was named one of the Mail & Guardian's Top 200 Young South Africans in 2012.

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