Influence of Ripeness of Banana on the Blood Glucose and Insulin Response in Type 2 Diabetic Subjects

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Abstract
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 I−1× 240 min) was significantly higher compared with under‐ripe banana (62 ± 17 mmol I−1× 240 min:p< 0.01) and over‐ripe banana (106 ± 17 mmol I−1× 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 I−1× 240 min (white bread), 7464 ± 1800 pmol I−1× 240 min (under‐ripe banana) and 8292 ± 2406 pmol I−1× 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.