Exclusively breastfeeding a baby till it is six months old could cut the risk of mother-to-child HIV transmission, scientists say.
The Human Immunodeficiency Virus (HIV) is a life-threatening condition in humans in which the immune system begins to fail.
Hoosen Coovadia and other researchers from the Africa Centre for Health and Population Studies at the University of KwaZulu-Natal, South Africa, compared solely breastfed babies with those also given formula or solid foods, reported the online edition of BBC News.
In the developed world, the risk of mother-to-child HIV transmission has been cut from 25 percent to under 2 percent because of the use of antiretroviral therapies, exclusive formula feeding and good healthcare support.
But these benefits are often unavailable in the developing world and exclusive breastfeeding is the best option for most women, the researchers said.
Breastfeeding remains a key intervention to reduce mortality and is also associated with fewer breast health problems.
The researchers said there was a four percent risk of post-natal transmission to infants who were just fed on breast milk between the age of six weeks and six months.
Infants who received formula milk or animal milk in addition to breast milk were nearly twice as likely to be infected as infants who received breast milk only.
And those given solids in addition to breast milk were almost 11 times more likely to acquire infection.
It is thought that this higher risk is due to the larger, more complex proteins found in solid foods that may lead to greater damage to the lining of the stomach, allowing the virus to pass through the gut wall.
Hoosen Coovadia of the Africa Centre said: "The question of whether or not to breastfeed is not a straightforward one.
"We know that breastfeeding carries with it a risk of transmitting HIV infection from mother to child, but breastfeeding remains a key intervention to reduce mortality."