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Riboflavin Excretions and Test Dose Returns of Young Women During Periods of Positive and Negative Nitrogen Balance

Department of Home Economics, University of Chicago, Illinois

Three young women were maintained on weighed diets for 3 periods of 10 days each. The daily nitrogen intakes were approximately 5 gm during the first period, 19 gm during the second and 5 gm during the third. The daily riboflavin intakes were approximately 1000 µg during the first period, 1200 to 1400 µg during the second and 1000 µg during the third. Urinary riboflavin and nitrogen excretions were determined daily; the amounts in foods and feces were determined on individual 5-day composites. Daily nitrogen balances were calculated by subtracting daily urinary excretions and average daily fecal excretions from average daily intakes.

The majority of the nitrogen balances were negative during the periods of low-nitrogen intake and all were positive during the period of high-nitrogen intake.

Daily riboflavin excretions varied inversely with the coexistent nitrogen balances. They represented from 40 to 60% of the riboflavin intake when the nitrogen balances were decidedly negative and approximately 7% of the intake when the nitrogen balances were strongly positive.

The returns of riboflavin test doses given at the end of each period showed the same inverse relationship with the nitrogen balances in 2 of the subjects.

Fecal riboflavin excretions did not appear to be influenced by the alterations in the composition of the diet and showed no relationship to the nitrogen balances.

Manuscript received 20 January 1947.