Baselines representing blood glucose clearance improve in vitro prediction of the glycaemic impact of customarily consumed food quantities

Abstract

Glycaemic responses to foods reflect the balance between glucose loading into, and its clearance from, the blood. Current in vitro methods for glycaemic analysis do not take into account the key role of glucose disposal. The present study aimed to develop a food intake-sensitive method for measuring the glycaemic impact of food quantities usually consumed, as the difference between release of glucose equivalents (GGE) from food during in vitro digestion and a corresponding estimate of clearance of them from the blood. Five foods -white bread, fruit bread, muesli bar, mashed potato and chickpeas -were consumed on three occasions by twenty volunteers to provide blood glucose response (BGR) curves. GGE release during in vitro digestion of the foods was also plotted. Glucose disposal rates estimated from downward slopes of the BGR curves allowed GGE dose-dependent cumulative glucose disposal to be calculated. By subtracting cumulative glucose disposal from cumulative in vitro GGE release, accuracy in predicting the in vivo glycaemic effect from in vitro GGE values was greatly improved.). Furthermore, the difference between the curves of cumulative GGE release and disposal closely mimicked in vivo incremental BGR curves. We conclude that valid measurement of the glycaemic impact of foods may be obtained in vitro, and expressed as grams of glucose equivalents per food quantity, by taking account not only of GGE release from food during in vitro digestion, but also of blood glucose clearance in response to the food quantity. Carbohydrate: Glycaemic impact: Glucose disposal: In vitro digestionFor practical consumer and dietetic use in glycaemia management, food values are required which will '. . . communicate glycaemic response in grams per serving of food' (1) , and which should be measured using '. . . validated in vitro methodology that accurately mimics in vivo behaviour' (2) . Current in vitro digestion methods for predicting relative glycaemic responses to foods measure carbohydrate that is rapidly available (for example, Englyst et al. ), or the area under the glucose release curve relative to a reference (5) . However, they cannot provide accurate or robust predictions of relative responses to whole foods varying in quantity, or accurately mimic the in vivo glycaemic response, because they do not allow for the effects of homeostasis. They do not take into account the fact that glycaemic responses to foods are a net effect of the balance between blood glucose loading and blood glucose disposal (GD), which depends dynamically on the rates of both. Not allowing for blood GD, and its dependence on the amount and rate of blood glucose loading, may lead to large inaccuracies when using glycaemic impact values from experimental portions to gauge the effect of the very different and varying food quantities that are consumed in a community setting. For instance, customarily consumed food portions often have a much lower glycaemic impact than would be expected from a glycaemic load value calculated from the glycaemic in...

Effect of Wholemeal Durum Wheat Varieties on Bread Quality

“…The digestion was carried out as described by Chillo et al [11] and Monro et al [12] with slight modifications. The methodology used and the experimental conditions were according to Mastromatteo et al [7].…”

Digestive analysis of processing effects on the glycaemic impact of oats in vitro

“…Predicted relative glycaemic response (GEGR), was determined from the in vitro digestion profile of GGE release per serving ( Fig. 3) over time, by diminishing the GGE loading at each time point by the estimated homeostatic glucose disposal at the time, the GGE disposal being dose-dependent and estimated using an equation generated from clinical studies time (Monro, Mishra, Venn, 2010). The equation used GGE released at 40 min to determine an appropriate GD rate, and was slightly modified in the present study so that the RO sample returned to baseline at 120 min, and the same modified equation was applied to analysis of all samples.…”

“…The digestion procedure involved a 30 min pepsin digestion, followed by pancreatic digestion during which aliquots were removed and made to 80% in ethanol at specified times, for measurement of released sugars and dextrins as glucose equivalents (GE). GE was measured as reducing sugar, against a glucose reference, in an aliquot of the 80% ethanol-soluble fraction after a secondary digestion with amyloglucosidase and invertase to convert dextrins and sucrose to monosaccharide (Monro, Mishra, Venn, 2010).…”

“…In addition, foods in which cereals are one of many ingredients may contain substantial quantities of sugars with lower glycaemic potency than glucose, such as sucrose (60% that of glucose) and fructose (22% that of glucose). Such sugars, nonetheless, contribute to the glycaemic response (Livesey, 2003) so should be counted in the glycaemic impact by converting them to grams of glucose equivalents with respect to glycaemic impact (GGE homeostatic, apparent blood glucose disposal (GD) reaction to blood glucose loading (Monro, Mishra, &Venn, 2010), because the postprandial glycaemic response results from a net excess of blood glucose loading over glucose disposal.…”

Glycaemic Impact Regulation Based on Progressive Geometric Changes in Solid Starch-Based Food Particles During Digestion

“…The release of glycaemic glucose equivalents from food into the gut during digestion has been termed its (relative) glycaemic impact (RGI) [4,20], and it has been repeatedly demonstrated to be a dominant factor determining the differences between foods in glycaemic potency [3,8,11,16,21]. High glycaemic impact in carbohydrate-based foods is often the result of removing the constraints of natural food structure, and of expanding the foods by processes such as leavening or high pressure extrusion, which produce highly porous matrices that allow rapid penetration of digestive enzymes.…”