Acute Effects of Substitution, and Addition, of Carbohydrates and Fat to Protein on Gastric Emptying, Blood Glucose, Gut Hormones, Appetite, and Energy Intake.

Caroline Giezenaar,Stijn Soenen,Kylie Lange,Trygve Hausken,Ian Chapman,Karen Jones,Michael Horowitz

doi:10.3390/nu10101451

Abstract

Whey protein, when ingested on its own, load-dependently slows gastric emptying and stimulates gut hormone concentrations in healthy young men. The aim of this study was to determine the effects of substitution, and addition, of carbohydrate (dextrose) and fat (olive oil) to whey protein. In randomized, double-blind order, 13 healthy young men (age: 23 ± 1 years, body mass index: 24 ± 1 kg/m2) ingested a control drink (450 mL; ~2 kcal/‘control’) or iso-volumetric drinks containing protein/carbohydrate/fat: (i) 14 g/28 g/12.4 g (280 kcal/‘M280′), (ii) 70 g/28 g/12.4 g (504kcal/‘M504′), and (iii) 70 g/0 g/0 g (280 kcal/‘P280′), on 4 separate study days. Gastric emptying (n = 11, 3D-ultrasonography), blood glucose, plasma insulin, ghrelin, cholecystokinin (CCK) and glucagon-like peptide-1 (GLP-1) concentrations (0–180 min), appetite (visual analogue scales), and ad-libitum buffet-meal energy intake (180–210 min) were determined. Substitution of protein with carbohydrate and fat was associated with faster gastric emptying (lower 50% emptying time (T50)), reduced suppression of ghrelin, and stimulation of GLP-1 (all P < 0.001); while the addition of carbohydrate and fat to protein did not affect gastric emptying or gut hormone responses significantly. Total energy intake (i.e., drink plus meal) was greater after all caloric drinks than control (P < 0.001). In conclusion, substitution of whey protein with dextrose and olive oil accelerated gastric emptying. Higher protein content of a mixed macronutrient drink increased gut hormone and insulin responses.

Highlights

The gastrointestinal tract plays a central role in determining appetite, energy intake, and postprandial glycemic excursions [1]
Our studies in healthy younger men have shown that whey protein, when infused intraduodenally, increases pyloric, and decreases antral and duodenal, motility, a pattern of contractions associated with retardation of gastric emptying [6,7]
The aim of this study was to determine the acute effects of substitution, and addition, of carbohydrate and fat to whey protein liquid supplements on gastric emptying, blood glucose and plasma insulin, ghrelin, CCK, and glucagon-like peptide-1 (GLP-1) concentrations, perceptions of appetite and gastrointestinal symptoms, and ad libitum energy intake at a buffet meal in healthy young men

Summary

Introduction

The gastrointestinal tract plays a central role in determining appetite, energy intake, and postprandial glycemic excursions [1]. Oral ingestion of whey protein alone load-dependently slows gastric emptying rates and increases plasma insulin, ghrelin, CCK, and GLP-1 concentrations in healthy young men [7]. The caloric rate of emptying of protein, carbohydrate, and fat, assessed by magnetic resonance imaging (MRI), may be similar when ingested alone [8], but protein and other macronutrients are seldom ingested in isolation It is, important to determine their effects on gastric emptying and other parameters when ingested in combination. There is evidence that protein evokes higher postprandial plasma CCK and GLP-1 responses and slows gastric emptying, as assessed by the acetaminophen absorption test, more than the other macronutrients, when ingested in a mixed macronutrient combination (yoghurt, 400 kcal, energy percent protein/carbohydrates/fat: 58/14/28% vs 19/47/34%) [9]. As determined by a 13 CO2 breath test, was comparable between a high- vs. low-fat breakfast

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