1. Introduction
kiwifruit reduced blood glucose, diabetes
SEPARATION, DIABETIC COMPLICATIONS, REACTIVE HYPOGLYCAEMIA, DIABETES
Postprandial glycaemic response amplitude plays a critical role in diabetic complications, but is subject to food order and temporal separation within a meal. Effects of partial fruit-for-cereal carbohydrate exchange on glycaemic and appetite responses, as affected by food order and separation, were examined using kiwifruit (KF) and wheaten breakfast cereal biscuit (WB). In a randomized cross-over intervention study, 20 subjects ingested 51.7 g of available carbohydrate as 74 g WB alone, or as 200 g KF and 37 g WB, each delivering 25.85 g of available carbohydrate. The 200 g KF was partially exchanged for 37 g of WB, at 90 min and 30 min before, at the same time as, or 30 min after, ingesting WB. Incremental satiety responses were derived from appetite scores measured using a visual analogue scale, and capillary blood glucose responses were monitored. In all exchanges, KF reduced the glycaemic response (iAUC) by 20–30% with no loss of total satiation. The incremental glycaemic and satiety responses to food ingestion followed each other closely. Glycaemic response amplitudes were reduced almost 50% compared with 74 g WB when KF ingestion preceded WB ingestion by 30 min, and less when the KF was ingested with or 30 min after the cereal. The results suggest that fruit most effectively suppresses the digestion of cereal carbohydrates if ingested long enough before the cereal to prevent overlap of the glycaemic responses, but close enough for fruit components that impede carbohydrate digestion or uptake to interact with the ingested cereal in the gut. Ethics approval was obtained from the Human and Disabilities Ethics Committee (HDEC) of the New Zealand Ministry of Health. The trial was registered with the Australian New Zealand Clinical Trials Registry (Trial ID: ACTRN12615000744550).Increased consumption of fruit has been recommended in the diets of people at risk of diabetes, partly because of a range of possible benefits arising from gut-level and systemic action of various fruit components [Our research on carbohydrate exchanges has shown that equi-carbohydrate partial substitution of breakfast cereal by kiwifruit reduced blood glucose peak height, delayed the onset of postprandial reactive hypoglycaemia, and maintained satiety. The kiwifruit therefore appeared to improve homeostatic blood glucose control in response to the meal. The antiglycaemic effect of fruit has been corroborated in other recent research [The antiglycaemic effect of fruit during the carbohydrate exchange of cereal can be partly explained by the substitution of relatively low glycaemic index fruit sugars (including fructose, GI = 21) for starch (GI = 70 in wheaten biscuit). Other fruit factors, shown in a human intervention study to include dietary fibre and organic acids [Because of the different mechanisms by which fruit might reduce digestion and absorption of carbohydrates, it is likely that the combination of gut processes that reduce glycaemic response will change with time after a meal. Therefore, the temporal separation of fruit and cereal intake in a meal could significantly modulate any antiglycaemic effect of the fruit. The impact of fruit organic acids may be immediate if their low pH inhibits gastric salivary amylase activity [Another aspect of glucose homeostasis that has been linked to the insulin response to blood glucose is appetite, and its converse, satiety [The above considerations raise the possibility that the glycaemic benefits of fruit substitution of cereal starch in a meal, by partial carbohydrate exchange, may depend on the timing of fruit ingestion relative to the cereal ingestion. Recent studies have shown that the order in which foods are consumed in a meal affects the glycaemic response and appetite and conclude that the ingestion of foods high in available carbohydrates should be concentrated towards the end of a meal [