Fatty acids have been shown to be immune-modulating and virucidal. They not only enhance the immune system but they participate directly in the immune system with activity that kills viruses.

The two essential fatty acids, linoleic and alpha-linlenic and their long-chain polyunsaturated fatty acids (LCPUFAs) derivatives, docosahexaenoic acid and arachidonic acid, are present in human milk. LCPUFAs have been shown to be essential for the development of T cell function in infants (Field et al. 2000) and arachidonic acid and other free fatty acids have been found to exhibit virucidal activity against encapsulated viruses in vitro (Kohn et al. 1980, Horowitz et al. 1988).

Shedding of HIV in human milk has been shown to be a strong predictor of HIV transmission (Koulinska et al. 2006, Rousseau et al. 2003, Semba et al. 1999, Fawzi et al. 2004).

In a study recently published in the American Journal of Clinical Nutrition, Villamor et al. looked at the amount of fatty acids (percentage weight concentration of fatty acids) in human milk and the concentration of cell-free or cell-associated HIV in milk to test the association of the risk of mother-to-child transmission (MTCT) of HIV (Villamor et al. 2007).

The design was a case-control study in a cohort of HIV-infected Tanzanian women and children (59 incident breastfeeding MTCT cases to 59 nontransmitting controls based on the child’s age at sample collection). The researchers quantified fatty acids, cell-free virus (CFV), and cell-associated virus (CAV) in a breastmilk sample collected before the infant’s first positive HIV test.

They found that after adjustment for indicators of maternal HIV disease stage, the risk of MTCT was inversely related (the lower the MTCT, the higher the fatty acid concentrations) to 11c,14c-eicosadienoic acid (an n-6 LCPUFA), arachidonic acid (an n-6 LCPUFA), and dihomo–linolenic acid (an n-3 LCPUFAs); the latter 2 were also linearly, inversely related to virus shedding in breast milk (the more of these, the less viral shedding measured). Lauric acid and pentadecanoic acid (saturated fatty acids) were associated with increased MTCT of HIV, whereas trans fatty acids were related to higher CAV and CFV (greater shedding of virus into the milk).

This study suggests that fatty acid composition of human milk might influence the shedding of the HIV virus and the MTCT of HIV. It appears that n-3 and n-6 LCPUFAs demonstrate a protective role whereas specific saturated and trans fatty acids influence outcomes more negatively.

There may be other individual fatty acids that impact MTCT transmission of HIV virus during breastfeeding. The effects of infant's gastric and lingual lipases on increasing direct anti-microbial activity in the intestinal tract (from the individual fatty acids released from triacylglycerols by these enzymes) cannot be overlooked (Isaacs 1986). Also, other pathogens that could disrupt mucosal barriers and facilitate HIV infection might be decreased by protective fatty acids (Isaacs 2005).

Finally, can maternal dietary modifications change breastmilk fatty acids concentrations to favor a decrease in MTCT of the HIV virus? Dietary factors do influence some breastmilk fatty acids such as a low-fat and high-carbohydrate diet stimulating lauric acid and other 10-14 carbon fatty acids to be produced in the mammary gland (Thompson et al. 1985, Hachey et al. 1989). Pentadecanoic acid is believed to originate directly from maternal diet with higher consumption of dairy products (Brevik 2005). However, the secretion of n-6 LCPUFAs in milk seems to depend more on mobilization from adipose tissue and endogenous synthesis and less on maternal dietary intake (Koletzko 1992). Additionally, regulatory mechanisms appear to keep the secretion of n-6 LCPUFAs in breastmilk constant but maternal supplementation with mixed n-6 and n-3 LCPUFAs has been found to increase breastmilk concentrations of arachidonic acid ( Smit et al. 2000.) Trans fats have been suggested to interfere with the synthesis of arachidonic acid and other LCPUFAs by inhibiting enzyme systems (et al. 1983).

More research on the role of maternal diet and fatty acid supplementation on MTCT of HIV virus is needed given that there are over 2.3 million HIV-infected children in the world with over 2 million of them living in sub-Saharan Africa where over 40% of all infant infections with HIV is due to MTCT during breastfeeding (UNAIDS/WHO 2006).

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