The n-6 to n-3 dietary fatty acid ratio has become unbalanced in large part due to increased intakes of n-6 fatty acid rich oils such as corn, sunflower and rape. This increase in n-6 fatty acids may be contributing to the rise in cases of lifestyle diseases such as cancer, cardiovascular disease and diabetes. Lowering the current n-6 to n-3 fatty acid ratio of the diet from 10 to 1 to around 3 to 1 has been shown in clinical trails to improve a number of biomarkers which are established risk factors for chronic disease. In addition, lowering the n-6 to n-3 fatty acid ratio during pregnancy, via supplementation with fish oils, has been shown to be largely beneficial to neonatal health. One particular area that has attracted attention is the effects of maternal n-3 intakes and the risk of postnatal allergy in the infant.
For example, researchers1 have investigated the effects of fish oils on maternal and neonatal immune responses. Pregnant women were randomly assigned to continue their habitual diet or receive 2 portions of salmon per week, providing roughly 2.45g of eicosapentanoic acid (EPA, C20:5 (n-3)) and docosahexanoic acid (DHA, C22:6 (n-3)), from week 20 of gestation to birth. Analysis of umbilical cord blood samples showed lower interleukin (IL)-2, IL-4, IL-5, IL-10 and tumour necrosis factor alpha (TNF-α) responses to phytohaemagglutinin, and lower IL-2 responses to Dermatophagoides pteronyssinus allergen 1 (Derp1) in the mononuclear cells of the treatment group. When a sub-group of cord blood was analysed from parents with high allergen phenotypes, lower IL-10 production in response to allergens (Toll-like receptor 2, 3 and 4 agonists, ovalbumin, salmon parvalbumin) and lower prostaglandin E2 and Derp1 production in response to lipopolysaccharide or phytohaemagglutinin was reported in the treatment group.
These results suggests that alteration in the n-6 to n-3 fatty acid ratio during pregnancy may modulate immune system elements associated with the allergy response. However the researchers did report that there was no significant difference in IgE, incidence of atopic dermatitis or skin prick test positivity at 6 months, and no significant difference in IgE response at birth, between the control and treatment groups. Therefore, the modulatory effects of fish oils may only be effective on the maternal immune system and on the foetus during gestation. It is known that n-3 fatty acids are able to cause the release of eicosanoid hormones that can modulate the release of immune regulatory chemicals such as the interleukins. For example, EPA and DHA can decrease production of prostaglandin E2, which is known to raise levels of IL-10. This explains the lower levels of interleukins in the treatment group.
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