Polyunsaturated fatty acid supplementation in infancy for the prevention of allergy.

Systematic review of randomized trials in infants enrolled in the first year of life without clinical allergy at baseline, including term and preterm infants, formula-fed and breastfed infants, and both lower-risk and high-risk populations. Some trials tested maternal PUFA supplementation during lactation or pregnancy rather than direct infant supplementation.

This review evaluated higher polyunsaturated fatty acid intake in infancy, either through direct infant supplementation or maternal supplementation during pregnancy or lactation, compared with control formulas or oils. Interventions included a range of PUFA formulations such as DHA and arachidonic acid, fish oil, gamma-linolenic acid, blackcurrant seed oil, and borage oil, with durations varying by trial.

PUFA supplementation in infancy did not show a clear overall reduction in allergic disease in infancy or childhood, and the certainty of evidence was very low. The review found no clear benefit for asthma, dermatitis/eczema, or food allergy. There was limited evidence that maternal PUFA supplementation may reduce infant incidence of allergic rhinitis, based on two studies totaling 594 infants: RR 0.47, 95% CI 0.23 to 0.96, I2 = 6%; RD -0.04, 95% CI -0.08 to -0.00; NNTB 25. For infant incidence of all allergic disease, one contributing study reported RR 0.96, 95% CI 0.73 to 1.26, and for infant food allergy across three studies the RR was 0.81, 95% CI 0.56 to 1.19.

The evidence base was very low quality and came from heterogeneous interventions, populations, and outcome definitions. Many outcomes were supported by only a few trials, follow-up into childhood was limited, and adverse events were not consistently reported in a way that allowed arm-specific extraction. The review also notes the need for larger, independent, high-quality trials with prespecified allergy outcomes and longer follow-up, especially in preterm and high-risk infants.