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Human Milk Studies

XXVII. Essential Amino Acids in Human Colostrum and Transitional Milk^1,2,3,

Research Laboratory of the Children's Fund of Michigan, Detroit

J. P. Pratt and B. M. Hamil

Departments of Obstetrics, Gynecology and Pediatrics, Henry Ford Hospital, Detroit, Michigan

The 10 essential amino acids were determined microbiologically in 38 samples of human colostrum and transitional milk secreted 2 to 10 days post partum. Samples were obtained from 10 women, each representing the composite mammary secretion from both breasts during 24 hours.

The amino acid concentrations per 100 ml of secretion varied with subject and day post partum and did not parallel changes in volume of secretion or concentration of total solids. Total nitrogen and amino acid concentrations followed the same general pattern, with highest values occurring on the 5th, 6th, 7th, or 8th day post partum. The ratios between the nitrogen of the essential amino acids and total nitrogen were not consistent, indicating the possibility of shifting proportions of the casein, lactalbumin, and globulin fractions of the total protein.

The same amino acids were determined in 133.6 ml of "first" colostrum, consisting of from a few drops to 4 ml of the first fluid from the breasts of each of 70 women, 8 to 24 hours post partum. Composites were also analyzed of the colostrum obtained from many of the women the first day and the second day following collection of the "first" secretion. In the "first" colostrum values for total solids, total nitrogen and the 10 essential amino acids were much higher than any values for human colostrum found in the literature. The percentage of total nitrogen represented by the amino nitrogen of the essential amino acids was higher than the corresponding values for the 24-hour collections of colostrum 2 to 10 days post partum. The greater percentages of amino nitrogen in the composites were accounted for by significantly higher values for arginine and threonine.

² The investigation represented in part by this paper was partially supported by a grant from the Nutrition Foundation, Inc., and was made possible by the cooperation of J. P. Pratt, M.D., Chief of the Department of Obstetrics and Gynecology, who selected the subjects and provided prenatal and obstetric care; Brenton M. Hamil, M.D., Department of Pediatrics, who provided medical care for the infants; Elizabeth Moran, R.N., Director of Nurses, who arranged special nursing service for the subjects; and Annie Lou Wertz, B.S., Dietitian, who aided in planning the dietary and securing the food samples for analyses, all of the Henry Ford Hospital, Detroit.

³ The authors are indebted to Max S. Dunn, Ph.D., Chemical Laboratory, University of California, Los Angeles, for the brochure of his microbiological methods prior to publication and for a sample of proline; and to the Rockefeller Foundation and Melville Sahyun, Ph.D., who provided other samples of amino acids.

Manuscript received 17 October 1949.