Fatty Acids In Breast Milk Reduce HIV Transmission Risk

BOSTON, Sept. 7 -- Supplementing breast milk with long-chain polyunsaturated fatty acids might reduce the risk of mothers giving HIV to their infants, researchers here said.

In a case-control study in Tanzania, nursing mothers with high levels of n-6 long-chain polyunsaturated fatty acids in their breast milk were less likely to pass on the virus than women with low levels, according to Eduardo Villamor, M.D., Dr.PH., of the Harvard School of Public Health.

The finding raises the possibility that interventions aimed at increasing the levels of such compounds could reduce the rate of mother-to-child transmission, Dr. Villamor and colleagues said in the September issue of the American Journal of Clinical Nutrition.

Breast milk is a common route for mother-to-child HIV transmission, the researchers said. While avoidance of breastfeeding blocks that route, it's not safe, sustainable, or affordable in many countries with high HIV rates, they said.

However, some mothers pass on the virus and others don't and the reasons for the difference are not well understood, Dr. Villamor and colleagues said.

To help fill the gap, they enrolled pregnant women taking part in a randomized controlled trial - the Tanzania Trial of Vitamins - that tested the effects of vitamins on mother-to-child transmission.

For the case-control study, they enrolled 58 women whose infants were HIV-negative before six weeks and positive afterwards and were, therefore, presumed to have been infected through breast milk.

The researchers analyzed the last breast milk sample before the child's first positive HIV test.

Controls were selected from the pool of women in the larger trial whose infants remained HIV-negative and were matched to the cases.

For the controls, the researchers analyzed the breast milk sample that was taken within a week of the sample from the matched case.

Compared with controls, cases had significantly lower CD4 cell counts at baseline and shed greater amounts of cell-free virus (CFV) or cell-associated virus (CAV).

After adjustment for CD4 count, clinical stage of HIV disease, and assignment to vitamin A supplementation, however, the risk of transmitting HIV was:

• Positively associated with percentage weight concentrations of the saturated fatty acids lauric acid and pentadecanoic acid.
• Inversely associated with higher percentage weight concentrations of the monounsaturated fatty acid gondoic acid and the n-6 long-chain compounds 11c,14c-eicosadienoic acid, dihomo-linolenic acid, and arachidonic acid.

For the n-6 acids, the risk of transmission was between 76% and 79% lower for women in the highest quartile compared with women in the lowest quartile, the researchers found.

The researchers cautioned that the causal nature of the associations remains uncertain, given that the study was observational. Randomized trials of interventions aimed at increasing levels of n-6 long-chain polyunsaturated fatty acids are needed, they added.

But "if these associations are found to be causal, the public health implications could be substantial," they said.