Variation in Riboflavin Excretion

Abstract

The variation in the excretion of riboflavin per hour, per gram of urinary creatinine, and per milliliter of urine has been studied in several subjects in which urine samples were collected every two or 4 hours. Regardless of the method of expressing the riboflavin excretion, single urine samples provide a poor estimate of the average excretion rate. The variation in excretion per hour and per gram of creatinine is of the same order of magnitude while the excretion per milliliter of urine is more variable in most subjects. The improvement in the estimates of the average excretion obtained by increasing the collection period or by multiple sampling has been calculated. Since the accuracy of the estimate improves as the length of the collection period is increased, field studies should attempt to collect urine over the longest convenient period. The variation from sample to sample is somewhat less in samples collected during the night than during the daytime. Thus, the most valuable sample should be that obtained upon rising in the morning. The limitations of urinary excretion data in the assessment of the nutritional status with regard to riboflavin for individuals or population groups have been discussed.