Urinary ascorbic acid excretion in the human as affected by dietary fiber and zinc

The objective of the project was to study the effect of dietary pectin, cellulose, hemicellulose, and zinc on human urinary excretion of ascorbic acid. The project consisted of two 33-day controlled feeding studies involving a total of 19 adult men and women normal health. Within each study all subjects received all experimental treatments. In study A during the four 7-day experimental periods the ground peanut based diets were varied as follows: no supplement, 14.2 g of hemicellulose supplement, 14.2 g of cellulose supplement, or 14.2 g of pectin supplement per subject per day. Mean urinary excretion of ascorbic acid by subjects while receiving these supplements were 26.10, 32.27, 26.27, or 20.60 mg/day, respectively. In study B during the four 7-day randomly arranged experimental periods, the following alterations were made to the basal diet: supplement of 14.2 g of pectin plus 1.3 g of zinc, 14.2 g of pectin plus 9.3 g of zinc, 4.2 g pectin plus 1.3 g of zinc, and 4.2 g of pectin plus 9.3 g of zinc. Mean urinary ascorbic acid excretion of subjects while receiving these diets were as follows: 20.61, 23.18, 28.07, 18.99. Hemicellulose supplement enhanced urinary excretion of ascorbic acid while pectin and zinc resulted in decreased urinary excretion of this vitamin. Increased urinary excretion of ascorbic acid at constant intake levels is thought usually to be indicative of enhanced absorption or of decreased need.