A new scientific study has shown that there is little evidence to support claims that garlic, onions, olive oil and the African potato are effective in the fight against HIV and Aids - and warned that they may even be harmful.
The University of Stellenbosch's Nutrition Information Centre (NICUS) on Monday released a report on whether food combinations and certain foods can play a role in arresting the advance of Aids in infected people.
It concentrated on the four products Health Minister Manto Tshabalala-Msimang has been promoting as beneficial to Aids patients.
Nicus said the safety of these foods, particularly that of extracts from the African potato, "has been questioned and remains a cause of serious concern".
"A study on the safety and efficacy of the hypoxis plant (African potato) extract in HIV-positive patients was terminated prematurely, and reported to the Medicines Control Council, because most of the patients who received the extract showed severe bone marrow suppression after eight weeks," the study found.
After an initial improvement, most patients became rapidly more ill.
Of far greater concern, Nicus said, was that the suspicion of hypoxis-induced immune suppression had been confirmed in cats' Aids, where they progressed and succumbed to full-blown Aids faster than those not treated by the hypoxis extract.
"At best, therefore, HIV/Aids patients should avoid any such supplements, until such time as their safety and efficacy, or otherwise, has been fully documented."
The researchers acknowledge that more information is needed on the effect of all four of the foodstuffs in relation to Aids.
On garlic, the researchers found that despite its known benefits, garlic extract supplements have been documented to interact with some of the anti-HIV drugs, reducing their effectiveness.
Certain forms of garlic powder produced damage to the stomach membranes, while raw garlic caused an increase in bleeding time in 50 healthy individuals.
The researchers found that olive oil can counteract the effects of certain Aids drugs which raise cholesterol.
But they said there is "no convincing or consistent scientific evidence that virgin olive oil boosts immunity or alters the course of HIV and Aids adversely or beneficially".
The report warns against "financially insecure" patients splashing out on olive oil, which "may limit the purchase of other affordable wholesome foods, which in turn is likely to adversely affect their nutritional status".
On onions, too, there is no evidence that it will enhance immunity or treat HIV-related symptoms effectively.
The report makes a number of recommendations on nutrition for Aids patients, such as frequent fruit and vegetable meals, daily intake of milk or yogurt and use of high energy drinks.