Proabsorptive effect of glycerol as a glucose substitute in oral rehydration solutions

We hypothesized that glycerol, a readily diffusable hydrophilic substance, may effectively substitute for glucose and enhance intestinal water and sod ium absorption in an oral rehydration solution (ORS). This was evaluated us ing a low osmolality (230-240 mOsm/kg) ORS containing 75 mmol/L sodium and a combination of glucose:glycerol (in mmol/L) 75:0, 50:25; 37.5:37.5, 25:50 , 10:65, or 0:75 during 3-hour long in vivo rat jejunal perfusions. Water, sodium, potassium, glucose and glycerol absorption, and unidirectional flui d movement (J(in), J(eff)) were determined Sodium and net water absorptions were maximal at glucose:glycerol ratios between 37.5:37.5 and 10:65 mmol/L . In the absence of glucose (0:75), absorption of water and electrolytes wa s lower than at any other concentration. The greater net rehydration seemed to be due to a higher J(in) as glycerol was increased up to 65 mmol/L. Pot assium absorption followed a similar pattern. With 50 mmol/L glycerol and 2 5 mmol/L glucose, there was a marked expansion of the lamina propria extrac ellular space and increased intercellular expansion between enterocytes. Th ese results indicate that glycerol may be an effective partial substitute f or glucose in ready-to-use ORS by producing an improved rate of water and e lectrolyte absorption. (J. Nutr. Biochem. 10:49-55, 1999) (C) Elsevier Scie nce Inc. 1999. All rights reserved.