Gastrointestinal Regulation of Water and Its Effect on Food Intake and Rate of Digestion

Abstract

An investigation was undertaken to determine the effects of water deprivation during meals in rats. Food intake, gastrointestinal solids water content, rate of digestion and tissue water content were studied. Rats fed without water ate less food than rats fed with water. The gastric contents of all animals fed with or without water was approximately 49% water and indicates close regulation of water in the gastric contents. When fed without water, rats regulate their food intake so that it matches the amount of water that they can mobilize from their own tissues thereby maintaining the proper water:food ratio in the gastric contents. How this is reflected in the mechanisms that control food intake is unknown. The water found in the gastrointestinal contents of rats fed without water is furnished by selected tissues, especially the skin, probably the adipose tissues and perhaps other tissues. The contents of the intestinal lumen contains about 76% of water in all the rats irrespective of the availability of water with meals. The total solids in the intestinal lumen of the rats eating without water averaged 0.39 gm and 0.52 gm for the rats eating with water. The regulation of both water and solids in the intestinal lumen indicates that it acts as though it were a part of the internal environment. Withholding of water during meals does not appear to interfere with digestion but it definitely decreases appetite and effects a reduction of food intake.