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Metabolism of Women During the Reproductive Cycle

IX. The Utilization of Riboflavin During Lactation¹

Four Figures

Research Laboratory, Children's Fund of Michigan, Detroit

Riboflavin was determined in composites exactly representing the food intakes of healthy nursing mothers during 5-day periods and in 24-hour collections of their milk and urine during the same intervals postpartum. The subjects were multiparas and received diets of comparable quality in amounts which satisfied their appetites.

The average daily intake of riboflavin was 3.1 mg per day. During the first 10 days postpartum, riboflavin secretion in milk increased with milk production, from an average of 0.01 to 0.49 mg per day. For the same women, the relationship of volume and riboflavin content continued during the periods of mature milk production. The average daily riboflavin secretion in mature milk was 0.29 mg.

While riboflavin secretion paralleled milk volume, the inclusion of liver in the diet of the fifth day of each 5-day period provided an intake of riboflavin 50% greater than the mean intakes for the other 4 days which produced only slight increases in secretion and excretion on the fifth day postpartum but augmented the amounts of riboflavin in milk and urine collected on the fifth day of all other 5-day periods.

While 3 to 32% of the average riboflavin intakes were found in the immature milk (first 10 days) and 3 to 15% of the intakes was secreted in mature milk, the excretion in urine during respective periods ranged from 12 to 82 and 26 to 61% of the intake. Together the milk and urine accounted for 15 to 108% of the intake.

² Now Professor, Department of Biochemistry, Cornell University, Ithaca, N.Y.

Manuscript received 20 May 1946.