Effect of Fasting, Self-Selected and Isocaloric Glucose and Fat Meals and Intravenous Feeding on Plasma Zinc Concentrations

Abstract

This study investigated the effect of fasting, self-selected meals and isocaloric oral glucose and fat meals and intravenous (i.v.) feeding on plasma zinc concentrations in men. Plasma zinc remained stable when volunteers fasted all day, but self-selected meals and 600 kCal of dextrose or fat emulsion caused significantly reduced plasma zinc concentrations [mean(SD) 12 · 1 (1 · 4), 12 · 3 (0 · 6) and 12 · 2 (0 · 7) μmol/L at 1400 h, respectively, compared with a fasting level of 13 · 9 (1 · 6) μmol/L at 0800 h, P < 0 · 05]. In patients undergoing intravenous hyperalimentation, plasma zinc decreased from 12 · 0(1 · 4) μmol/L at 0800 h to 10 · 0 (1 · 1) μmol/L at 1400 h [mean(SD), P < 0 · 01]. These data show that both enteral and i.v. feeding cause a decline in plasma zinc and that glucose alone is not responsible for this post-prandial fall since ingestion of isocaloric amounts of glucose or fat have a similar effect.