The Academy of Science of South Africa found "no evidence that healthier eating is any substitute for correctly-used medical drugs".
"The panel has concluded that no food, no component made from food, and no food supplement has been identified in any credible study as an effective alternative to appropriate medication," said lead researcher Barry Mendelow.
South Africa's Health Minister Manto Tshabalala-Msimang has often claimed that the use of garlic, lemon and other vegetables -- earning her the nickname Dr Beetroot -- could contain the epidemic.
"These delay the development of HIV to AIDS-defining conditions, and that's the truth," she told parliament last year.
Dan Ncayiyana, editor of the South African Medical Journal and one of the authors of the study, said: "One of our most important findings has been that nutrition is important for general health but is not sufficient to contain the HIV/AIDS or the turberculosis epidemic."
The report called for nutritional studies to be conducted in conditions found in most poor countries where much of the population is malnourished.
"The few randomised trials that exist have mainly been conducted in high-income countries where most patients are well nourished and have access to life-prolonging antiretroviral therapy," the report said.
The health ministry said the study "reaffirms" government's position in its effort to combat the disease.
"It reaffirms some of the policy positions (on HIV/AIDS) pushed by government and the department," health spokesman Sibani Mngadi told SABC radio.
"While we are facing challenges of two major infectious diseases, nutrition will assist you in promoting good health, (but) you need to get appropriate medication."
South Africa is one of the countries worst-hit by HIV with prevalence standing at 18.4 percent in 2006, and with 5.41 million people living with the illness.