INFLUENCE OF RIPENESS OF BANANA ON THE BLOOD-GLUCOSE AND INSULIN-RESPONSE IN TYPE-2 DIABETIC SUBJECTS

Banana is a popular and tasty fruit which often is restricted in the diet prescribed for diabetic patients owing to the high content of free sugars. However, in under-ripe bananas starch constitutes 80-90%. of the carbohydrate content, which as the banana ripens changes into free sugars. To study the effect of ripening on the postprandial blood glucose and insulin responses to banana, 10 type 2 (non-insulin-dependent) diabetic subjects consumed three meals, consisting of 120 g under-ripe banana, 120 g over-ripe banana or 40 g white bread on separate days. The mean postprandial blood glucose response area to white bread (181 +/- 45 mmol l-1 x 240 min) was significantly higher compared with under-ripe banana (62 +/- 17 mmol l-1 x 240 min: p < 0.01) and over-ripe banana (106 +/- 1 7 mmol l-1 x 240 min: p < 0.01). Glycaemic indices of the under-ripe and over-ripe bananas differed (43 +/- 10 and 74 +/- 9: p < 0.01). The mean insulin response areas to the three meals were similar: 6618 +/- 1398 pmol l-1 x 240 min (white bread), 7464 +/-1800 pmol l-1 x 240 min (under-ripe banana) and 8292 +/- 2406 pmol l-1 x 240 min (over-ripe banana). The low glycaemic response of under-ripe compared with over-ripe bananas may be ascribed to the high starch content, which has previously been found to be only hydrolysed slowly by alfa-amylase in humans. In conclusion, bananas, particularly under-ripe, contain low glycaemic carbohydrates which are a cheap source of carbohydrate and an acceptable alternative as between-meal snacks for Type 2 diabetic subjects.