Variations of lactose and oligosaccharides in human milk were studied over a 3-month lactation period by dialysis, chromatography on Bio-gel P-2 column, paper chroma-tography, colorimetric analysis and gas chromatography. Milk samples were collected from donors of various blood and secretor types. An increase in the concentration of lactose was noted: 59.25 ± 1.61 to 72.17 ± 1.35 g/l for the group of secretor A secretor Le^aLe^b individuals, and from 62.25 ± 1.35 to 73.15 ± 3.45 g/l for the group of secretor H secretor Le^a Le^b individuals. A decrease in the concentration of oligosaccharides was also found: from 16.71 ± 0.99 to 7.90 ± 1.29 g/l and from 18.51 ± 0.74 to 7.33 ± 0.65 g/l, respectively, for these same groups. In secretor H nonsecretor Lewis individuals, the concentration of lactose increased from 67.97 ± 3.09 to 77.42 ± 1.88 g/l, and the concentration of oligosaccharides decreased from 13.27 ± 0.40 to 3.47 ± 0.33 g/l. Analysis of oligosaccharide composition by chromatography showed that variations are in relation to the secretor Lewis type. All oligosaccharides decreased equally throughout the lactation period, regardless of the blood group. The decrease was more rapid, however, in the nonsecretor Lewis individuals. In these individuals, the absence of certain oligosaccharides is not compensated by an overproduction of the other oligosaccharides present or by biosynthesis of structurally different oligosaccharides. The origin of these oligosaccharides is discussed.

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Variations of lactose and oligosaccharides in human milk were studied during the day and the feed, by dialysis, chromatography on Bio-gel P-2 column, paper chromatography, colorimetric analysis and gas chromatography. Progressive changes were found during the day, but not during the feed. A diurnal variation in milk lactose was seen, which was the inverse of the oligosaccharides. Significant negative correlations between lactose and oligosaccharides were seen in the afternoon and evening (p < 0.05). The minimal mean value of lactose at 19.00 h is 58.64 ± 5.28 g/l and the maximal mean values of oligosaccharides was 17.93 ± 2.28 g/l. The data are discussed with regard to other milk constituents and to their possible physiological relevance.

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