Blood insulin, glucose, fructose and gastric inhibitory polypeptide levels in carbohydrate-sensitive and normal men given a sucrose or invert sugar tolerance test.

Twelve carbohydrate-sensitive and 12 normal men were selected for the study. Carbohydrate-sensitivity was based on an abnormal insulin response to a sucrose load. The subjects were fed a diet consisting of 45% of the calories as carbohydrate, 40% fat and 15% protein for 5 days prior to a sucrose or invert sugar tolerance test. In a crossover design, subjects were given 2 g/kg body weight of sucrose or invert sugar, and responses of insulin, glucose, fructose and gastric inhibitory polypeptide (GIP) were determined. Blood samples were taken at 0, 0.5, 1, 2 and 3 hours after being given the test loads. Insulin and glucose levels were significantly higher in carbohydrate-sensitive as compared to normal men. Glucose and GIP did not show any significant differences between the two carbohydrate loads. At 1 hour, the carbohydrate-sensitive men given sucrose had significantly higher insulin levels than carbohydrate-sensitive men given invert sugar (disaccharide effect). At 1, 2 and 3 hours, the disaccharide effect was shown in the fructose levels of the carbohydrate-sensitive men. In normal men, the disaccharide effect with levels of fructose was seen at 0.5 and 3 hours. This study indicates that the disaccharide effect on blood insulin cannot be explained by differences in gastric inhibitory polypeptide in unadapted human subjects.