The executive director of the UN's World Food Program, James Morris, says that although the region had seen bumper crops, it had actually made the task of the UN agency more difficult.
"Good harvests do not necessarily mean people have enough to eat," Mr Morris said in a statement issued in Johannesburg.
"Food and good nutrition are crucial in battling against HIV/AIDS but it is very tough to convince the international community of the complexity and depth of the pandemic in this region, especially when people's misery is masked by green fields and good harvests," he said.
Donor assistance
Many people in the region, which had been plagued by drought in recent years, will remain dependent on donor assistance.
The UN says they are either still unable to grow enough food to feed themselves until the next harvest or they can not afford to buy food available at markets and shops.
Over the last five years the WFP has had to assist up to 13 million people left hungry by erratic weather, poor government policies, economic stagnation and shortages of seeds and fertilisers.
Many households were forced to sell assets such as chickens, goats, cattle and even cooking pots to survive.
"Unlike crises elsewhere, the humanitarian challenges caused by HIV/AIDS in southern Africa will linger on for generations," Mr Morris said.
"Desperate hungry people should not have to compete for international assistance according to their level of deprivation. Turning away from people devastated by AIDS because of other crises should not be an option for the international community."
Countries in southern Africa have the highest HIV/AIDS rates in the world and many people are simply too ill or too young to work the land or earn an income, the WFP said.
What cash many HIV/AIDS affected families have is spent on medicines or funerals.
The UN AIDS agency estimates that close to 15 million people, or 38 percent of the worldwide total, are living with the disease.
Orphan numbers increase
There are increasing numbers of orphans and households where children are left to fend for themselves, placing an additional burden on family structures, communities and the state, the WFP said.
The WFP was also concerned that food surpluses in the region would be bought by traders from east Africa, where there are drought-related food shortages, rather than sold at more affordable prices at home.
"Orphans and other vulnerable children are a particular concern for WFP as most governments can't cope with the overwhelming number of people who need help," Mr Morris said.
"Food assistance for these children is their lifeline. Our support to them and the other vulnerable groups must be steadfast."
Indications are that climate change brought on by global warming will further undermine food security for millions of southern Africans in coming years.