Maternal diet and fatty acids in human milk: results of the MELK study

PURPOSE: Human milk is the preferred nutrition for infants. Maternal diet influences its fatty acid composition particularly fish-derived fatty acids and polyunsaturated fatty acids (PUFAs). Evidence for other fatty acids and associations with micronutrient intake remains inconsistent. This study examines associations between maternal macro- and micronutrient intake and human milk fatty acid composition. METHODS: Data of 109 breastfeeding mothers was collected. Dietary intake was assessed using repeated 24-h food records and a short food frequency questionnaire. Nutrient intakes were calculated using the Dutch food composition database. Human milk samples were collected at 6-8 weeks postpartum following a standardized protocol, and fatty acid concentrations were analyzed using ISO16958:2015. Associations between maternal diet and human milk fatty acids were evaluated using beta regression. The MELK study is registered at the ISRCTN registry (ISRCTN35735283). RESULTS: Higher maternal intakes of n-3 PUFAs, n-6 PUFAs, and trans fatty acids (TFAs) were associated with higher proportions in milk. Milk total saturated fatty acids (SFA) were inversely associated with most dietary fatty acid groups. At the individual level, higher SFA intake was positively associated with several milk SFAs, while higher TFA intake was linked to higher palmitic acid in milk, intake of n-3 PUFA showed the opposite pattern. Higher micronutrient intake was associated with increased milk PUFA levels and lower SFA and TFA levels. CONCLUSION: This study provides further detail on links between maternal dietary fatty acids and their levels in human milk, and suggests that micronutrient and vitamin intake may also influence milk fatty acids.