Changes in the polyunsaturated fatty acids of breast milk from mothers of full-term infants over 30 wk of lactation.

The fatty acid composition of breast milk from 23 breast-feeding women was serially assessed by capillary gas chromatography from the 6th to the 30th wk of lactation. The proportions of total n-3 and n-6 fatty acids were unchanged with time, although some significant differences were noted for individual polyunsaturated fatty acids (PUFAs). Of the n-3 PUFAs, only docosahexaenoic acid (DHA, 22:6n-3) concentrations changed, decreasing between 6 and 16 wk from 0.26 +/- 0.13% to 0.21 +/- 0.13% of total fatty acids but remaining at this proportion until 30 wk. Of the n-6 PUFAs, 18:3, 20:3, 20:4, and 22:5 all showed reductions with time. Compared with concentrations observed in a 1981 study, linoleic acid was higher (14% compared with 11% of total fatty acids), whereas the concentration of DHA was lower (0.21% compared with 0.32% of total fatty acids), possibly reflecting a general change in the diets of Australian women.