AIM: to investigate the profile and the contents of FA, especially of long chain (LC)-PUFA, in breast milk during prolonged lactation.

SUBJECTS AND METHODS: recruitment of mothers after delivery of full-term infants (>37-42 weeks gestational age). Collection of pooled breast milk (hindmilk) over 24 hours at the first day (colostrum), at 1, 3, 6 and 9 months of lactation. Lipid extraction by chloroform-methanol and analysis of FA methyl esters (weight%) by capillary gas-chromatography. Values are expressed as mean±SD. Preliminary data from 32 mothers are here reported.

RESULTS: total milk lipids raise from 1.29±0.7 to 5.96±3.1 g/dl from colostrum to the 3rd month, and remain constant afterward. The percentages of 18-C essential PUFA do not change, while the major modifications concern the 20-C LC-PUFA up to the 3rd month. Among n-6 PUFA, 20:3 and 20:4 significantly decrease (from 0.76±0.29 to 0.41±0.06 and from 0.98±0.22 to 0.50±0.07 respectively). In addition, levels of 20:3 n-9 fall from 0.87±0.06 to 0.14±0.04. In the n-3 series, a rise of 20:5 takes place in concomitance with reduction of 22:6 levels.

CONCLUSIONS: the high levels of 20-C LC-PUFA, including 20:3 n-9 but not 20:5 n-3, in colostrum are an index of the high demand for these components by the infants during the period of the highest growth rate.