Circadian variation and changes after a meal in volume and lipid production of human milk from rural Mexican women.

This research was designed to evaluate the circadian variation in the lipid content of the milk obtained from 10 lactating Mexican women as well as the effects of a meal eaten by the mother and of previous milk sampling on the milk volume and fat yield. In addition, predictions were made to determine the most appropriate sampling schedule to obtain a milk sample representative of 24-hour production. Every 4 h over a 24-hour period, the contents of the left breast of predominantly breast-feeding volunteers were completely extracted, using an Engell pump, and analysed for lipid content. In a separate experiment, 6 volunteers were sampled hourly from 9.00 to 13.00 h on 2 consecutive days, one after eating breakfast and the second while fasting. Significant circadian variations of volume (p < 0.05) and lipid yield (p < 0.001) were noted, peaking at 8.00-12.00 and 16.00-20.00 h, respectively. No effects of eating breakfast or of the volume and fat content of the preceding pumping on the actual volume or fat yield were found. In this population, sampling at 12.00, 20.00 and 24.00 h is the most representative of the 24-hour lipid yield, tending to overestimate it by 2.59 g/24 h with a predictive range of 97-124%.