Potential sex differences in human milk fatty acids and their association with atopic dermatitis: Results of the Ulm SPATZ health study

Abstract Background Polyunsaturated fatty acids (PUFAs) in human milk are essential in immune system maturation and might play a role in the development of allergic conditions, such as atopic dermatitis (AD) in infants. Immune system responses are modulated by sex, but data on the sex‐specific associations with PUFAs are limited. We therefore explored sex‐specific differences in human milk PUFAs and their association with AD up to 2 years. Methods PUFAs were measured in human milk samples from the Ulm SPATZ Health Study at 6 weeks ( n = 512) and 6 months ( n = 367). Associations with AD up to 2 years were evaluated using crude and multivariable logistic regression. Interactions between infant sex and PUFAs were explored by including the product term. Results No significant associations were observed with 6‐week data. At 6 months, the median relative proportion of docosahexaenoic acid (DHA) was significantly higher in milk for female than male infants ( p = .001). Female infants whose milk was lower in quintile proportions of alpha‐linolenic acid (ALA) at 6 months had lower odds of AD compared to males [first vs. fifth quintile OR (95% confidence interval): 0.13 (0.02, 0.66), p = .02]. This interaction was not significant when correcting for multiple testing (α threshold: p = .004). No other statistically significant associations were observed. Conclusion Individual quintile PUFA proportions in human milk were not associated with AD, overall and in a sex‐specific manner. More comprehensive and statistically powered longitudinal studies are needed to determine whether potential sex differences in human milk, if any, could be of clinical relevance for infants including the investigation of mediating factors.