Abstract
Kiwifruit is a carbohydrate food of low glycaemic potency which could potentially be exchanged for starch-based foods in management of postprandial glycaemia. The effect of equicarbohydrate partial exchange of kiwifruit varieties 'Hayward' green (GR) and 'Zesy002' (SunGold; SG) for a starchy wheat-based breakfast cereal (WB) on the characteristics of the postprandial glycaemic response and satiety was therefore determined. A total of twenty non-diabetic subjects (mean age 36 years; mean BMI 24·5kg/m2) consumed four meals, each containing 40g available carbohydrate, in random order, after an overnight fast. The meals were: (1) glucose; (2) 70·29g breakfast cereal; (3) 200g of GR plus breakfast cereal (30·93g); and (4) 200g of SG plus breakfast cereal (27·06g). Throughout the 180min postprandial period, capillary blood glucose concentrations were monitored, and satiety rated by a visual analogue scale. Partial kiwifruit substitution of WB significantly reduced postprandial glycaemic response amplitude (glucose, 3·91; WB, 3·66; WB+GR, 2·36; WB+SG, 2·31 mmol/l; least significant difference (LSD) 0·64; P<0·001) and incremental area under the blood glucose response curve (0-120min) (glucose, 228; WB, 180; WB+GR, 133; WB+SG, 134mmol/l×min; LSD 22·7; P<0·001). The area between baseline and response remained positive in kiwifruit-substituted meals but became negative after 120min with glucose and WB, indicating that kiwifruit improved homeostatic control. Kiwifruit substitution of cereal did not significantly reduce satiety. We conclude that either 'Hayward' or 'Zesy002' kiwifruit may be used in equicarbohydrate partial substitution of starchy staple foods to reduce glycaemic response and improve glucose homeostasis without decreasing satiety.
Highlights
Kiwifruit is a carbohydrate food of low glycaemic potency which could potentially be exchanged for starch-based foods in management of postprandial glycaemia
In a previous study (JA Monro, H Edwards, S Mishra, D Hedderley and J Podd, unpublished results) of the effects of kiwifruit on the blood glucose response to a glycaemic breakfast cereal, we found that breakfast cereal plus kiwifruit caused a lower glycaemic response than breakfast cereal plus the same amount of sugars, of the same monosaccharide composition, as in the kiwifruit
The kiwifruit appeared to be having an effect on the blood glucose response profile by mechanisms unrelated to its sugar component, but possibly related to other factors such as organic acids, phenolics and dietary fibre properties that might differ between cultivars
Summary
Kiwifruit is a carbohydrate food of low glycaemic potency which could potentially be exchanged for starch-based foods in management of postprandial glycaemia. The effect of equicarbohydrate partial exchange of kiwifruit varieties ‘Hayward’ green (GR) and ‘Zesy002’ (SunGold; SG) for a starchy wheatbased breakfast cereal (WB) on the characteristics of the postprandial glycaemic response and satiety was determined. We conclude that either ‘Hayward’ or ‘Zesy002’ kiwifruit may be used in equicarbohydrate partial substitution of starchy staple foods to reduce glycaemic response and improve glucose homeostasis without decreasing satiety. The fruit carbohydrate should replace a carbohydrate of equal or higher glycaemic index to avoid increasing glycaemic response.When the substitution involves kiwifruit partially substituting readily digested starch in a processed cereal-based product, such as wheat biscuit (glycaemic index (GI) = 70), one could expect a substantial lowering of the glycaemic response, because the fruit sugars are approximately half fructose (GI of about 22)(9), and other components of the fruit further reduce glycaemic response, as discussed above, giving whole kiwifruit a low GI of about 50(9)
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