After a meal containing sucrose, the plasma glucose rises, reaching a peak within 15-30 min, and returns to baseline within 2 h. The classification of carbohydrates as sugars or starches does not predict the magnitude of this response. In the past it was assumed that refined sucrose caused a more rapid rise in blood glucose levels than starchy foods or naturally occurring sources of sugars like fruit. This view has been shown to be incorrect. Most starchy foods, including potatoes, bread, and many packaged breakfast cereals, are digested and absorbed rapidly and the blood glucose response is almost as high as that seen with an equivalent load of pure glucose. Foods containing refined sucrose, such as soft drinks and ice cream, have been shown to give moderate rises in blood glucose. Furthermore, the glycemic response to foods containing refined sugars is similar to that of foods containing naturally occurring sugars.
The 'glycemic index' approach has been used to classify foods according to their ability to raise the level of glucose in the blood. Foods are tested in equivalent carbohydrate portions according to standardized methodology. On a scale where glucose = 1GG, the glycemic index of refined sucrose (= 65) is similar to that of white bread (= 7G). Table 3 shows the glycemic index of a range of common foods. Refined sucrose elicits an insulin response commensurate with its glycemic response, i.e., it does not stimulate inappropriately high insulin secretion.
See also: Carbohydrates: Chemistry and Classification; Regulation of Metabolism; Requirements and Dietary Importance. Dental Disease. Diabetes Mellitus: Classification and Chemical Pathology; Dietary Management. Fructose. Glucose: Chemistry and Dietary Sources; Metabolism and Maintenance of Blood Glucose Level. Glycemic Index.
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