Klemens CM, Berman DR, Mozurkewich EL. (2011) BJOG. 118(8): 916-25.
BACKGROUND: Maternal supplementation with omega-3 polyunsaturated fatty acids (n-3 PUFA) may modulate immune responses and allergy in neonates and children.
OBJECTIVE: To determine if n-3 PUFA supplementation during pregnancy and lactation reduces risk for childhood allergic disease.
SEARCH STRATEGY: We searched Medline and all evidence-based medicine reviews for randomised controlled trials comparing the effects of n-3 PUFA and placebo supplementation during pregnancy and/or lactation on childhood allergic diseases and inflammatory cytokines.
SELECTION CRITERIA: We included studies reporting on food allergy, response to the egg skin prick test (SPT), atopy and asthma in infancy and childhood as well as production of interleukin-13 and interferon-gamma, two cytokines involved in the pathogenesis of asthma. For assessment of inclusion, two authors reviewed all abstracts for suitability and independently extracted data.
DATA COLLECTION AND ANALYSIS: Two-by-two tables were constructed and odds ratios (OR) were calculated for the outcomes: response to the SPT, food allergy, atopy and asthma in childhood. The assays differed so data on inflammatory markers were reported in narrative form.
MAIN RESULTS: Five randomised controlled trials (n = 949) were included. n-3 PUFA supplementation during pregnancy reduced 12-month prevalence of positive egg SPT (two trials, 12/87 versus 32/100, OR 0.33, 95% CI 0.16, 0.70) and childhood asthma (two trials, 10/303 versus 17/179, OR 0.349, 95% CI 0.154, 0.788) and significantly reduced cord blood interleukin-13 levels. Supplementation during lactation did not prevent asthma, food allergy or atopy.
CONCLUSION: n-3 PUFA supplementation during pregnancy decreases childhood asthma and response to SPT.
The prevalence of childhood allergic diseases (including food allergies, asthma, eczema and other atopic conditions) has increased substantially in developed countries in recent years, and represents a significant health burden, so the need for effective prevention strategies has become acute.
This systematic review of controlled trials found that dietary supplementation during pregnancy with long-chain omega-3 fatty acids (found in fish and seafood) can reduce both asthma and allergic sensitisation to eggs in infants. No benefits were found for supplementation during the postnatal period, suggesting that timing may be a key factor.
Omega-3 are essential nutrients known to have anti-inflammatory effects, but they have been displaced in western-type diets by omega-6 fats (which have pro-inflammatory effects).
This review provides further evidence that an increased dietary intake of omega-3 during pregnancy can have significant benefits for children's health and development. Only 5 clinical trials were included, however (involving 949 children), of which only 2 yielded measures of asthma or egg-sensitisation, and only one involved postnatal supplementation. This means that further research in this area is urgently needed to confirm and extend these findings, although some additional large trials are due to be reported on within the next year.
Meanwhile, this review of well-controlled trials - in keeping with many other studies - shows that omega-3 supplementation during pregnancy appears to be safe for both mother and infant, and may have other benefits. Fish and seafood are the best natural dietary sources of long-chain omega-3, although current dietary recommendations for pregnant women would make it difficult to obtain the amounts used in these trials.