Study of lactose in human colostrum transitional and mature milk

The purpose of this study was to analyze the lactose content in human colostrum, transitional, and mature milk, including predelivery colostrum. A review of literature showed that most studies reporting the constituents of human milk were done 20 years ago. The majority reported average lactose levels in the mature milk of many women. Pew studies have been done on the day-to-day changes in an individual mother's milk throughout the course of lactation or of the predelivery secretions. Two normal, healthy women were selected as subjects for this study. Milk samples were collected daily from approximately 2 weeks prior to delivery until 5 weeks following delivery. Prior to delivery total colostrum was expressed from both breasts every 8 hours and pooled for a 2lj.-hour specimen. This same procedure was carried out following delivery, but with samples of fore" and "hind" milk expressed from each breast. Lactose content was determined using the method of Polin and Wu (1920). The results of this investigation showed values of lactose similar to those reported in earlier studies. The major difference was in the values of the predelivery colostrum. Both subjects demonstrated higher levels of lactose during this period than were reported by other investigators. In addition, the lactose content varied considerably, not only between subjects but from day to day in the same subject. A sharp rise in lactose content was observed in both subjects between 12 and 7 days prior to delivery. The subject who generally demonstrated higher lactose levels before delivery reached her mature level earlier than did the other subject. Both subjects showed a steady increase in the lactose content from predelivery colostrum to mature milk. Variations between subjects and from day to day in the same subject became less as the milk matured.