Kiwifruit, carbohydrate availability, and the glycemic response

An appreciable proportion, about 10%, of the dry weight of kiwifruit consists of primary cell walls. About 80% of dry matter is available carbohydrate consisting of glucose, fructose, and sucrose, and about 10% is digestible protein. The cell wall component, being nonstarch polysaccharide, is undigested in the stomach and small intestine, so the component increases in relative concentration in the gut lumen where its physicochemical properties may be important in modulating carbohydrate digestion and absorption. Released from the constraint of fruit structure, the dietary fiber swells to four times its original volume during in vitro digestion. When the digested remnants are allowed to settle into a packed but uncompressed state, as in the gut, they reduce the rate of glucose diffusion by about 40% and profoundly reduce digesta mixing, especially in the presence of a low background of soluble viscous polysaccharide. An in vitro estimation of the glycemic index (GI) of carbohydrate in kiwifruit, and in vivo estimates show the carbohydrate to be of low GI. On a whole fruit basis because of the high water content of kiwifruit, a 100g kiwifruit would be equivalent to about 5g (1 teaspoon) of glucose in its effect on blood glucose; thus, kiwifruit have low glycemic impact and are suitable for those with diabetes.