Abstract
BackgroundThere is recent evidence that glucose delivered to the distal small intestine (SI) may stimulate the ileal brake and inhibit appetite. High polyphenolic grape extract (PGE) has been shown to inhibit α-amylase and α-glucosidase activity, two key enzymes required for starch digestion, in vitro. It is hypothesised to slow digestion and absorption of starch in the proximal SI such that glucose may be delivered distally into the ileum and suppress appetite. This study investigated the safety and efficacy of a PGE supplement, delivered within a capsule and consumed with a high-starch breakfast, on appetite ratings and ad libitum energy intake (EI) at a subsequent lunch meal.MethodsTwenty healthy, non-obese (BMI 18–28 kg/m2) male volunteers participated in a randomised, double blind, placebo controlled, three arm, cross-over study. Participants were administered (i) low dose PGE500 (500 mg), (ii) high dose PGE1500 (1500 mg), and (iii) matched placebo with a 2MJ high-starch breakfast (white bread); followed 3 h later by a single item buffet-style lunch meal (pasta and meat sauce). Outcome variables were feelings of hunger, fullness, prospective thoughts of food (TOF) and satisfaction assessed using visual analogue scales (VAS); and ad lib energy and macronutrient intake at the lunch meal.ResultsThere was no detectable effect of PGE500 or PGE1500 compared with placebo (all, time*supplement interaction, P > 0.05) on VAS-assessed hunger, fullness, TOF or satisfaction. There was also no evidence that PGE significantly altered ad lib energy or macronutrient intake at the lunch meal relative to placebo (P > 0.05). EI following PGE500 was +164 kJ higher than placebo (+5.3 %, P > 0.05); and EI following PGE1500was −51 kJ lower than placebo (−1.7 %, P > 0.05).ConclusionsWhilst well tolerated, there was no evidence that encapsulated low dose PGE500 or high dose PGE1500 consumed with a high starch breakfast meal altered postprandial hunger, fullness, TOF or satisfaction relative to a matched placebo. Nor was there evidence that either dose altered ad lib energy or macronutrient intake at an outcome meal.Trial registrationACTRN12614000041651
Highlights
There is recent evidence that glucose delivered to the distal small intestine (SI) may stimulate the ileal brake and inhibit appetite
There was no significant difference between supplements (ANOVA, P > 0.05), no evidence that polyphenolic grape extract (PGE) at either dose when delivered within a capsule and with a starch-rich breakfast meal significantly altered energy intake (EI) relative to placebo
Grape extracts are widely consumed as a nutritional supplement worldwide, are generally regarded as safe (GRAS) [14, 15, 42] and in our present study we were able to confirm the tolerability of PGE doses ranging from 500 to 1500 mg in healthy males
Summary
There is recent evidence that glucose delivered to the distal small intestine (SI) may stimulate the ileal brake and inhibit appetite. There is a growing body of evidence from both animal and clinical studies that infusing glucose directly into the ileum can modify a range of GI activities, and that in turn this may put a brake on food intake [8] Achieving this effect with food is extremely challenging as the digestion and absorption of CHO occurs mainly in the stomach, duodenum and jejunum of the proximal SI, or fore gut, resulting in minimal delivery of monosaccharide glucose into the ileum [8,9,10]. The initial step in the enzymatic digestion of starch involves cleavage of the glucoseglucose α-(1, 4) glycosidic bond by α-amylase to produce shorter dextrin chains and glucose-glucose disaccharides (such as maltose and isomaltose) These products are further hydrolysed into individual glucose units by a set of brush border enzymes collectively called α-glucosidases. These monosaccharide forms of CHO are taken up by gut epithelial cells using specific transporters, sodium/glucose cotransporter 1 (sGLT1) and glucose transporter 2 (GLUT2) [11, 12]
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