Metabolic Patterns in Preadolescent Children: XIV. Excretion of Niacin or Tryptophan Metabolites by Girls Fed Controlled Diets Supplemented with Nicotinamide

Abstract

A metabolic study was carried out with twelve 7- to 9-year-old girls maintained with 5 controlled diets varying in niacin content from 10 to 31 mg/day. The adjustment diet and two of the four experimental diets were supplemented with crystalline nicotinamide in gelatin capsules. Urinary excretion of N1-methyl-nicotinamide, N1-methyl-2-pyridone-5-carboxamide, niacin, and quinolinic acid were measured during an adjustment period and during 6 consecutive 6-day experimental periods. Subjects fed a low-protein, low-riboflavin diet or a moderate-protein, adequate-riboflavin diet supplemented with 10.3 mg/day of nicotinamide excreted 8.9 and 8.2 mg more of niacin metabolites (NM) per day than did girls fed the same diets without supplemental niacin. The girls fed the low-protein, low-riboflavin diet supplemented with crystalline nicotinamide excreted more NM than predicted from a regression equation. Thus it is possible that the low protein or riboflavin content, or both, of this diet resulted in a lowered requirement for niacin by these subjects or interfered with their utilization of the added nicotinamide. Almost constant excretion of NM was attained after the girls were fed the controlled diets for only 6 days.