Intake and gastric emptying of mono- versus disaccharides by rats

Eating and gastric emptying of mono- versus disaccharides were measured in rats which consumed each day a carbohydrate solution and, 5 h later, a restricted amount of a nutritionally adequate dry diet. When Wistar rats were offered 30% (wt/vol) sugar solutions for 60 min a day, energy intakes were smaller for glucose than for maltose or dextrin and smaller for invert sugar (fructose + glucose) than for sucrose. Sprague-Dawley rats consumed less energy from glucose than maltose when fed 60%, but not 15%, solutions of these sugars. Among Wistar rats accustomed to hypotonic carbohydrate meals, gastric emptying (kilocalories/minute) was slower for 30% glucose than 30% maltose and for 63% maltose than 21% maltose. These differences became obscured with continued exposure to highly hypertonic meals. Monosaccharides, being small, highly soluble molecules, can impart great osmolality to stomach contents. It appears that this osmotic property of monosaccharides tends to slow eating and gastric emptying.