Aim To investigate the association between trans isomeric and polyunsaturated fatty acids (PUFAs) in human milk samples determined in a large cohort of lactating mothers.
Methods Human milk samples of mothers participating in a large birth cohort study in Germany were investigated both at the 6th week (n = 769, age: 31.4 [4.8] years, BMI at the beginning of pregnancy: 23.3 [3.7] kg/m2) and at the 6th month of lactation (n = 462). Fatty acid composition of milk samples was determined by high-resolution capillary gas chromatography.
Results We found no inverse correlations between trans hexadecenoic acid (C16:1n-7t) and linoleic acid (C18:2n-6), arachidonic acid (C20:4n-6), alpha-linolenic acid (C18:3n-3) and docosahexaenoic acid (C22:6n-3). In contrast, there were almost uniformly significant inverse correlations between trans octadecenoic acid (C18:1n-7/9t) and the sum of trans isomeric fatty acids and the investigated n-3 and n-6 PUFAs both at the 6th week and the 6th month of lactation (table).
Our results suggest that trans isomeric fatty acids may interfere with the availability of essential fatty acids and arachidonic acid in mature human milk not only at the 6th week, but even at the 6th month of lactation.