he quality of maternal nutrition during pregnancy is increasingly being found to influence the risk of disease in adult life for the offspring. Nutrition during the time following birth has also been indemnified as being pivotal to future disease outcomes, because it has been shown that the nutrition of the mother can greatly influence the quality of the breast milk consumed by the infant. Maternal nutrition during this time is therefore of utmost importance. Fish and fish oils are foods that appears to have a strong influence on the nutritional value of breast milk, and studies show that high intakes of oily fish can increase the eicosapentanoic acid (EPA, C20:5(n-3)) and docosahexanoic acid (DHA, C22:6 (n-3)) content of breast milk. These long chain polyunsaturated fatty acids may be particularly important for infant brain development, with DHA being strongly implicated in this role.
Many studies have shown that the maternal dietary n-3 fatty acid intake can influence the fatty acid content of breast milk. For example, in one study1, researchers investigated the effects of salmon consumption on the composition of breast milk by feeding expectant mothers 2 portions of fish per week for 20 weeks before birth. A second group of women was allowed to eat their habitual diet to act as controls. Those consuming the salmon were estimated to be consuming a mean intake of 3.45 g of long chain n-3 fatty acids per week. The results showed that the breast milk of the group eating salmon had 80 % higher concentrations of EPA, 90 % higher levels of DHA and 30 % higher levels of docosapentanoic acid (DPA, C22:5 (n-3)) compared to the control group. This was reflected in a lower n-6 to n-3 fatty acid ratio in the breast milk of the salmon group.
These results support many previous studies to show that fish oils can influence the fatty acid composition of breast milk. Interestingly, the researchers also showed that fish oil consumption caused a significant reduction in secretory immunoglobulin A (sIgA) compared to the controls. The implications of this result are not known, and it is unclear why fish oil consumption should lower the sIgA content of the breast milk. Infants do not produce their own IgA until 30 days following birth, and so these result may be significant. Fish oil may lower the sIgA content of milk through regulation of arachidonic acid, which is known to mediate PGE2 synthesis which can influence immunoglobulin production. However, fish oil supplements do not cause this decrease in sIgA. Therefore, the highly contaminated nature of farmed salmon may have played a role in altering the immune status of the mothers.
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