Raisins are a low to moderate glycemic index food with a correspondingly low insulin index

The objective of this study was to determine the glycemic index (GI) and insulin index (II) of raisins and evaluate if these values are similar in different populations. The study subjects consisted of 10 healthy sedentary individuals (S; age, 25.7 +/- 1.3 years; body mass index [BMI] = 23.3 +/- 1.7 kg/m(2)), 11 aerobically trained adults (A; age, 23.1 +/- 1.0 years; BMI = 24.1 +/- 0.3 kg/m(2)), and 10 prediabetic adults (P; age, 50.0 +/- 2.6 years; BMI = 32.6 +/- 1.9 kg/m(2)). Subjects consumed 50 g of available carbohydrate from raisins and from a glucose solution (reference food) on 2 separate occasions. Serum glucose and insulin concentrations were measured from capillary fingerstick blood samples at baseline and at 15, 30, 45, 60, 90, and 120 minutes (and 150 and 180 minutes for P group) postprandially. The GI of raisins was low (GI, < or = 55) in the S (49.4 +/- 7.4) and P (49.6 +/- 4.8) groups and was moderate (GI, 55-69) in the A group (62.3 +/- 10.5), but there were no differences among the subject groups (P = .437). The II of raisins was 47.3 +/- 9.4, 51.9 +/- 6.5, and 54.4 +/- 8.9 for the S, A, and P groups, respectively. On average, the A group secreted 2- to 2.5-fold less insulin per gram of carbohydrate compared with the S and P groups (P < .05). Thus, raisins are a low to moderate GI food, with a correspondingly low II. The lower insulin response in the A group compared with the other groups suggests enhanced insulin sensitivity.