Breastfeeding transmission less likely if breast milk high in omega-6 fats

Women with HIV appear less likely to transmit HIV if their breast milk contains high levels of the omega-6 fatty acids (polyunsaturates), possibly because the fatty acids reduce HIV levels, researchers from the United States and Tanzania report in the August edition of the American Journal of Clinical Nutrition.

Breast milk contains a host of nutrients essential for infant development, among them polyunsaturated fatty acids (PUFAs), which play a key role in the development of the newborn baby’s T-cell functions.

Exclusive breastfeeding is recommended for HIV-positive women until their child is six months old, based on evidence from several studies showing that it provides significant protection against common infections for infants - even though it poses a continued risk of HIV infection - when compared with formula feeding.

Identifying which factors might make exclusive breastfeeding safer is an important research priority, since provision of antiretroviral therapy to mothers during the breastfeeding period in order to limit HIV transmission, although highly protective, is still far from a reality in most settings.

The study matched 59 women who transmitted HIV to their infants through breastfeeding within a larger Tanzanian study of mother-to-child transmission against 59 women who did not transmit HIV.

Samples of breast milk from each woman were analysed to quantify the levels of fatty acids and HIV. Unsurprisingly women in the transmitter group had significantly lower CD4 cell counts and higher viral load in breast milk, both factors that have been associated with HIV transmission through breastfeeding in previous studies.

Multivariate analysis showed that women with high levels of several omega-6 PUFAs had a significantly lower risk of transmitting HIV through breastfeeding. The strongest relationship was apparent with arachidonic acid and with D-linolenic acid.

Women in the highest quartile of concentrations of these PUFAS had a risk of mother-to-child transmission that was between 76% and 79% of the risk observed among women in the lowest quartile of PUFA concentrations.

The researchers also found that trans-fatty acids, found in hydrogenated fats like margarine and known to have a harmful effect on cardiovascular health, seemed to be linked to increased levels of cell-free and cell-associated HIV in breast milk, although the effect was not statistically significant. The authors speculate that at higher levels of dietary intake – as seen in North America and Europe – these fats might show a stronger association.

At this stage the authors say, it is not possible to prove that high levels of PUFAs reduce HIV levels.

However, if PUFAs do reduce HIV levels, the next step is likely to be a study examining the effect of dietary supplementation, the authors say. Research to identify the other factors that lead to variations between women in PUFA levels in breast milk, such as genetics, will also be needed. Also, research into PUFA levels in children may show that PUFAs protect them against infection from HIV in breast milk.