Fish oil may help reduce allergies among infants

Allergic diseases such as asthma have dramatically increased in Western countries over the last 20 to 30 years, often attributed to changes in lifestyle, such as diet.

The researchers theorised that the Western world tends to eat much less oily fish. Furthermore, there is also increasing evidence that the failure of normal immune regulation that characterises allergy occurs in early life, they write in the December issue of the Journal of Allergy and Clinical Immunology​ (vol 112, no 6).

Janet Dunstan and colleagues examined the effect of fish oil supplementation in 40 pregnant women (from 20 weeks gestation to delivery) on the immune response in their infants. The women all had a history of hay fever or asthma, making their children at increased risk of developing allergies. A further 43 women took an olive oil placebo.

The supplements resulted in significantly higher levels of omega-3 and lower levels of omega-6 polyunsaturated fatty acids in cell membranes of babies born to mothers in the fish oil group. Although for the most part it was not statistically significant, mononuclear cells taken from the umbilical cord of these babies generally had weaker immune response to allergens, reported the researchers.

They found that at one year of age, the offspring of mothers who had taken fish oil supplements were three times less likely be sensitised to egg allergen, and though they were more likely to develop atopic dermatitis, they were 10 times less likely to have severe disease.

Mothers who supplement their diet with fatty acids rich in docosahexaenoic acid (DHA) during pregnancy and lactation may also increase the IQ of their children, according to recent studies.

The authors of the new study note that "more detailed follow-up studies are required in larger cohorts to establish the robustness of their findings and to ascertain their significance in relation to longer-term modification of allergic disease in children"​.

German researchers recently said they had found further evidence that components of diet, particularly fatty acids and antioxidants, might be able to inhibit symptoms of hay fever in adults, which affects up to 20 per cent of the UK's population. They reported a positive association between high intake of oleic acid and hay fever whereas high intake of eicosapentaenoic acid was inversely related to the symptoms.

Probiotics, more widely studied for allergy protection than fish oil, have been shown to protect children from atopic eczema for up to four years when given to pregnant women and babies around the time of childbirth.