Availability of Riboflavin of Ice Cream, Peas, and Almonds Judged by Urinary Excretion of the Vitamin by Women Subjects

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Abstract
Eight healthy women subjects participated in 5 experimental studies in which the relative availability of the riboflavin present in ice cream, frozen green peas, and almonds was determined. During a 12-day period when a weighed diet containing 2.4 mg of riboflavin was ingested, the urinary excretion of riboflavin was strikingly constant. Administration of 2 mg of riboflavin by retention enema on the morning of the eleventh day produced no change in the amount of riboflavin which appeared in the urine. A marked rise in the concentration of riboflavin of the urine occurred for all subjects when two 500 µg portions of pure riboflavin supplemented the basal diet. The percentage of the test dose returned varied from 31 to 67 with an average value of 42% for the 8 subjects. When a supplement of 1 mg of riboflavin was supplied in the form of ice cream, the increment in urinary riboflavin was comparable to that produced by the pure vitamin, indicating that the riboflavin of ice cream was nearly as available as that of the pure vitamin. When either frozen green peas or almonds furnished 1 mg of the supplementary vitamin, considerably less riboflavin was excreted in the urine than when the pure vitamin was administered. Less than one-half as much riboflavin appeared to be absorbed from these foods as had been absorbed from ice cream or the pure vitamin. Investigations are under way to determine some of the factors which influence the availability of riboflavin in foods.