Fish Oil Does Not Prevent Early Allergies in Infants

Diedtra Henderson

September 04, 2012

September 4, 2012 — Giving infants relatively high doses of fish oil in the first 6 months of life modestly increases their levels of omega 3 polyunsaturated fatty acids (n-3 PUFAs) but does not prevent them from developing childhood allergic disease, according to the findings of a randomized controlled trial.

The finding, by N. D'Vaz, BSc, from the School of Paediatrics and Child Health at the University of Western Australia in Perth, and coauthors was published online September 3 in Pediatrics.

Changing Western lifestyles have been implicated in an epidemic of allergic diseases, but teasing out the influence of specific environmental drivers has been difficult. Dietary changes are thought to be a major contributor, with keen interest paid to the drop in n-3 PUFA levels in diets while consumption of omega 6 PUFAs rises.

Researchers know from observational and interventional studies that supplementing pregnant women's diets with fish oil helps infants stave off allergies. D'Vaz and colleagues explored whether giving fish oil to infants younger than 6 months would have the same protective effect.

They recruited 420 mothers in their 36th week of pregnancy from private and public metropolitan prenatal clinics between January 6, 2005, and January 10, 2008. The women had allergies and restricted fish intake but were not smokers. After birth, 218 infants were randomly assigned to receive a daily supplement containing 650 mg fish oil, squirted from a capsule into their mouths before the first morning feeding. Another 202 infants in the control group got a daily squirt of olive oil.

Because of the discontinuation of one product, the final 27 children received similar capsules of fish oil from a different supplier. At the end of the intervention period, there was no significant difference in the infants' levels of erythrocyte docosahexaenoic acid (DHA) or eicosapentaenoic acid (EPA).

Infants were evaluated at 6 and 12 months of age, and information about such respiratory symptoms as recurrent wheezing, asthma, and rhinitis were collected at the same intervals.

"At the end of the intervention, erythrocyte levels of DHA (P = .03) and EPA (P = .016) were significantly higher in the fish oil group compared with the control group," as were plasma levels, the authors write. By 12 months of age, however, there were no differences in prevalence of any allergic disease, sensitization (overall or specific), eczema, or food allergy between infants in the fish oil or control groups.

"Our results show that although the postnatal fish oil intervention was associated with potentially favorable effects on immune function at 6 months...it did not achieve a reduction in the development of allergic disease in the first 12 months of life," the research team writes. The finding is in line with a previous study that found that giving fish oil to infants older than 6 months had no effect on reducing allergic outcomes.

Limitations included nonadherence. Sixty-two participants withdrew before the end of the study and/or did not wish to attend clinical visits. Of participants who withdrew, 18.3% were in the fish oil group compared with 10.9% in the placebo group (P = .031). Even flavoring both types of capsules with vanilla did not stop 92.2% of parents from correctly guessing their infants were in the fish oil group.

In addition, despite the relatively high doses of n-3 PUFA used in the study, levels recorded in the infants only show a modest increase, suggesting issues with bioavailability and absorption of the ethyl ester supplements. Finally, olive oil may not have been the optimal control choice, as it has some immunomodulatory effects.

"[W]ith emerging evidence of more allergy protective effects of [long-chain PUFA] in pregnancy compared with the postnatal period, we suggest that optimizing n-3 PUFA status remains desirable but best achieved through promoting maternal n-3 PUFA intake during pregnancy possibly in conjunction with lactation," the authors conclude.

The study was financially supported by the National Health and Medical Research Council of Australia. The authors have disclosed no relevant financial relationships.

Pediatrics. Published online September 3, 2012. Abstract

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