Methods of Quantifying the Glycemic Index of Raisins in Three Populations: 1948

The glycemic index (GI) of raisins was determined in three groups according to standardized methodology that is based on the calculation of positive incremental area under the curve (AUC). In addition, two other potential methods of calculating GI were evaluated: 1) baseline-adjusted peak (peak – baseline); and 2) excursion (peak – lowest). PURPOSE: To test the hypothesis that differences in GI calculations (AUC, baseline adjusted peak, and the excursion method) exist among three different subject populations (S=sedentary, A=athlete, P=pre-diabetic). METHODS: The S group (n=1 0, 25.7±1.3 years, BMI=21.7±1.7 kg/m2), A group (n=11, 23.1±1.0years, BMI=24.1±0.4 kg/m2), andPgroup (n=10, 50.0±2.6 years, BMI=32.6±1.9 kg/m2) consumed 50 g of available carbohydrates via raisins or a glucose solution on two separate occasions. Finger-stick blood samples (∼1 ml) were obtained at 0, 15, 30,45,60, 90, 120 min (+150 & 180 min for P) postprandially and analyzed for serum glucose levels. RESULTS: Calculations of GI in Three Populations.TableData are presented as mean ± SEM The GI of raisins, based on AUC, was low (GI<55) in both the S and P groups and was only slightly higher in the A group. In the S group, both baseline-adjusted peak and excursion resulted in higher GI values as compared to AUC, thus supporting the hypothesis. In addition, the P group had a significantly higher baseline adjusted GI when compared to AUC. The hypothesis was not supported in the A group, where no differences were found. CONCLUSION: The AUC method of calculating GI is influenced by the overall time of glucose elevation. The other methods represent postprandial glucose at two points in time. Therefore, considering the significant differences detected among computation techniques in S and P groups, time may be an important factor. However, for the A group, a calculation technique incorporating time may not be as critical.