Acute effects of raisin consumption on glucose and insulin reponses in healthy individuals

Abstract

Raisins are popular snacks with a favourable nutrient profile, being high in dietary fibre, polyphenols and a number of vitamins and minerals, in addition to being rich in fructose. In light of evidence demonstrating improvements in glycaemic control with moderate fructose intake and low-glycaemic index (GI) fruits, our aim was to determine the GI, insulin index (II) and postprandial responses to raisins in an acute feeding setting. A total of ten healthy participants (four male and six female) consumed breakfast study meals on four occasions over a 2- to 8-week period: meal 1: white bread (WB) (108 g WB; 50 g available carbohydrate) served as the control and was consumed on two separate occasions; meal 2: raisins (R50) (69 g raisins; 50 g available carbohydrate); and meal 3: raisins (R20) (one serving, 28 g raisins; 20 g available carbohydrate). Postprandial glucose and insulin were measured over a 2 h period for the determination of GI, glycaemic load (GL) and II. The raisin meals, R50 and R20, resulted in significantly reduced postprandial glucose and insulin responses when compared with WB (P < 0·05). Furthermore, raisins were determined to be low-GI, -GL and -II foods. The favourable effect of raisins on postprandial glycaemic response, their insulin-sparing effect and low GI combined with their other metabolic benefits may indicate that raisins are a healthy choice not only for the general population but also for individuals with diabetes or insulin resistance.

Keywords: Dried fruit; GI, glycaemic index; GL, glycaemic load; Glycaemic index; Glycaemic load; R20, raisins (20 g available carbohydrate); R50, raisins (50 g available carbohydrate); Raisins; WB, white bread; iAUC, incremental AUC.

Figures

Fig. 1.

Postprandial glucose responses to three meals containing 50, 50 and 20 g of available carbohydrates from white bread (○), raisins (•) and raisins (∆), respectively. Values are means, with standard errors represented by vertical bars. a,b,cMean values at a specific time point with unlike letters were significantly different (P < 0·05).

Fig. 2.

Incremental AUC (iAUC) for glucose after consumption of three meals containing 50, 50 and 20 g of available carbohydrates from white bread (WB), raisins (R50) and raisins (R20), respectively. Values are means, with standard errors represented by vertical bars. a,b,cMean values with unlike letters were significantly different (P < 0·05).

Fig. 3.

Postprandial insulin responses to three meals containing 50, 50 and 20 g of available carbohydrates from white bread (♦), raisins () and raisins (■), respectively. Values are means, with standard errors represented by vertical bars. a,b,cMean values at a specific time point with unlike letters were significantly different (P < 0·05).

Fig. 4.

Incremental AUC (iAUC) for insulin after consumption of three meals containing 50, 50 and 20 g of available carbohydrates from white bread (WB), raisins (R50) and raisins (R20), respectively. Values are means, with standard errors represented by vertical bars. a,b,cMean values with unlike letters were significantly different (P < 0·05).