HIV-positive moms have long been told to feed their infants formula to avoid transmitting HIV via breast milk. But a South African study has found that breastfeeding exclusively during the first six months of life is the safest choice in many places where contaminated formula and food commonly spread deadly diarrhea. Formula-fed babies die at about twice the rate of those on breast milk in such areas. What's more, the study found that the risk of HIV transmission is ten times lower when infants in developing countries had breast milk alone than if they had other food as well.

Study leader Hoosen Coovadia, MD, lists a few possible reasons for the surprising news. Breast milk has nutritional and immunity building benefits. Exclusive breast feeding also produces milk with lower HIV levels by continously draining the breasts. And it minimizes breast damage such as bleeding nipples, further dropping transmission risk. Whatever the cause, infant-feeding guideline for positive moms in developing nations are being revised as a result.

But ladies, don't try this at home. In the United States and other nations with clean food and water, breast feeding is not recommended for positive mothers. "When the formula is safe, use it," says Dr. Coovadia. "There's still a risk of HIV transmission with exclusive breastfeeding."