Are the glycemic and insulinemic index values of carbohydrate foods similar in healthy control, hyperinsulinemic and type 2 diabetic patients?

Background/Objectives: a criticism of glycemic index (GI) is that it does not indicate the insulin response of foods (insulinemic index, II). However, it is unknown if the GI and II values of foods are equivalent in all subjects, a necessary criterion for clinical utility. We compared GI and II values in non-diabetic subjects with fasting-serum-insulin (FSI) <40 pmol/l (healthy control) or with FSI >= 40 pmol/l (hyper[I]) and subjects with type 2 diabetes (T2DM), and to see whether GI and II were related to the serum-glucose concentrations, insulin sensitivity, beta-cell function and hepatic insulin extraction (HIE) of the subjects. Subjects/Methods: Serum-glucose, -insulin and -C-peptide responses after 50 g available-carbohydrate portions of glucose (tested three times by each subject), sucrose, instant mashed-potato, white-bread, polished-rice and pearled-barley were measured in healthy control (n = 9), hyper[I] (n = 12) and T2DM (n = 10) subjects. Results: Food GI values did not differ significantly among the three subject groups, whereas II values were higher in T2DM (100 +/- 7) than healthy controls (78 +/- 5) and hyper[I] subjects (70 +/- 5) (mean +/- s.e.m., P=0.05). II was inversely associated with insulin sensitivity (r=-0.66, P<0.0001) and positively related to fasting-and postprandial-glucose (both r=0.68, P<0.0001) and HIE (r=0.62, P = 0.0002). In contrast, GI was not related to any of the biomarkers (P>0.05). Conclusion: The GI is a valid property of foods because its value is similar in healthy control, hyper [I] and T2DM subjects, and is independent of subjects' metabolic status. However, II may depend upon the glycaemic control, insulin sensitivity and HIE of the subjects. European Journal of Clinical Nutrition (2011) 65, 727-734; doi:10.1038/ejcn.2011.28; published online 23 March 2011