Intestinal Absorption

As fluids leave the stomach and enter the small intestine, the water and carbohydrate that make up the solution must pass through the intestinal mucosa for take-up by blood. The main factor influencing the speed with which water and carbohydrate are absorbed is the concentration of carbohydrate in the solution that enters the intestines.³² Slightly lower concentrations of carbohydrate and electrolytes, relative to the concentration of plasma, result in faster absorption of water than a solution that has either a much higher or much lower concentration.³³ A 6 to 7 percent carbohydrate solution appears to offer the best balance for speedy absorption. Consumption of highly concentrated carbohydrate solutions during exercise may cause a temporary shift of fluids away from muscle cells and into the intestines to dilute the solution before absorption. This would have a negative impact on both muscle function and sweat rates because it would cause, at least temporarily, a degree of plasma and tissue dehydration.