Breast milk fatty acid composition differs between overweight and normal weight women: the STEPS Study.

OBJECTIVE: We studied differences in breast milk fatty acid (FA) composition between overweight and normal weight women and the effect of FA composition on children's cholesterol concentrations at 13 months and growth from birth to 13 months. METHODS: Samples were collected from lactating women (n = 100) participating in STEPS study at infant's age of 3 months, and FA composition was analyzed with gas chromatography. Diet of mother was studied with Index of Diet Quality at third trimester of pregnancy and with food frequency questionnaire on sampling day. The children's weights and heights were collected from hospital records at birth and during study visits at 13 months. RESULTS: Overweight women's breast milk compared to normal weight women's breast milk contained higher amount of saturated FAs (46.3 vs. 43.6 %, P = 0.012), lower amount of n-3FAs (2.2 vs. 2.7 %, P = 0.010), lower ratio of unsaturated to saturated FAs (1.1 vs. 1.3, P = 0.008), and higher ratio of n-6 to n-3 FAs (5.7 vs. 4.9, P = 0.031) than those of normal weight women even after adjusting for maternal diet (P < 0.05 for all). Normal weight women adhered more to dietary recommendations during pregnancy, whereas no differences were found in diet at sampling 3 months postpartum. The children's weight gains correlated with saturated FAs (R = 0.22, P = 0.04) and the ratio of unsaturated to saturated FAs (R = -0.23, P = 0.038) in milk; however, effects diminished after adjusting for total duration of breastfeeding. Milk FA composition was not associated with children's cholesterol concentrations at 13 months. CONCLUSIONS: Breast milk FA composition differed between overweight and normal weight women.