Normal meals are highly viscous, and viscosity is a key factor in influencing gastric emptying of food. However, the process of meal dilution and mixing is difficult to assess with the use of conventional methods. The aim of this study was to validate an in vivo, novel, noninvasive, echo-planar magnetic resonance imaging (EPI) technique, capable of monitoring the viscosity of a model meal, and to use this to investigate the effects of viscosity on gastric emptying, meal dilution and satiety. Healthy volunteers (n = 8) ingested 500 mL of locust bean gum (0.25, 0.5, 1.0 or 1.5 g/100 g), nonnutrient, liquid meals of varying viscosities, and labeled with a nonabsorbable marker, phenol red. Meal viscosity was calibrated against the water proton transverse relaxation rate (T(2)(-1)) in vitro before ingestion, thus viscosity was measured in vivo via EPI measurements of T(2)(-1). Viscosity and dilution were also measured directly using nasogastric aspirates. Gastric volumes as measured by EPI, fullness, appetite and hunger were also assessed serially. Before ingestion, the log of initial meal viscosity was linearly related to T(2)(-1) (n = 8, r(2) = 0.95). Similarly, T(2)(-1) measured in vivo was also linearly related to the viscosity of the aspirates (r(2) = 0.88). All meals underwent rapid dilution, leading to a reduction in viscosity, which was greatest for the most viscous meal (P < 0.01). Surprisingly, despite the fact that the initial meal viscosity varied 1000-fold, there was only a small delay in gastric emptying (P for trend < 0.05). The area under the curve for satiety increased with initial meal viscosity, whereas that for hunger decreased (P < 0.05). In conclusion, the viscosity of a meal in vivo can be measured noninvasively using EPI. The stomach responds to meal ingestion by rapid intragastric dilution, causing a reduction of meal viscosity, and gastric emptying is minimally delayed. However, increased viscosity is associated with more prolonged satiety.
RC. Enhancement of intragastric acid stability of a fat emulsion meal delays gastric emptying and increases cholecystokinin release and gallbladder contraction. Am J Physiol Gastrointest Liver Physiol 292: G1607-G1613, 2007. First published March 1, 2007; doi:10.1152/ajpgi.00452.2006.-Preprocessed fatty foods often contain calories added as a fat emulsion stabilized by emulsifiers. Emulsion stability in the acidic gastric environment can readily be manipulated by altering emulsifier chemistry. We tested the hypothesis that it would be possible to control gastric emptying, CCK release, and satiety by varying intragastric fat emulsion stability. Nine healthy volunteers received a test meal on two occasions, comprising a 500-ml 15% oil emulsion with 2.5% of one of two emulsifiers that produced emulsions that were either stable (meal A) or unstable (meal B) in the acid gastric environment. Gastric emptying and gallbladder volume changes were assessed by MRI. CCK plasma levels were measured and satiety scores were recorded. Meal B layered rapidly owing to fat emulsion breakdown. The gastric half-emptying time of the aqueous phase was faster for meal B (72 Ϯ 13 min) than for meal A (171 Ϯ 35 min, P Ͻ 0.008). Meal A released more CCK than meal B (integrated areas, respectively 1,095 Ϯ 244 and 531 Ϯ 111 pmol ⅐ min ⅐ l Ϫ1 , P Ͻ 0.02), induced a greater gallbladder contraction (P Ͻ 0.02), and decreased postprandial appetite (P Ͻ 0.05), although no significant differences were observed in fullness and hunger. We conclude that acid-stable emulsions delayed gastric emptying and increased postprandial CCK levels and gallbladder contraction, whereas acid-instability led to rapid layering of fat in the gastric lumen with accelerated gastric emptying, lower CCK levels, and reduced gallbladder contraction. Manipulation of the acid stability of fat emulsion added to preprocessed foods could maximize satiety signaling and, in turn, help to reduce overconsumption of calories. gastric emptying; lipid; magnetic resonance imaging CONSUMPTION OF PREPROCESSED foods high in added fat is steadily increasing in the developed countries. Fatty foods have high energy density and palatability but exert a relatively weak effect on satiation (compared calorie per calorie with protein and carbohydrate loads), which may encourage calorie overconsumption (5). This, in turn, may be one important factor contributing to the current epidemic of obesity in the Western population (38). Weight gain management rightly focuses on a healthy balanced diet, sensible portion sizes, and exercise. However, it would be desirable also to be able to maximize the satiating properties of fatty meals themselves. This could help to reduce postprandial hunger and, in turn, snacking, and it could also lead to improved design of slimming products.Manipulating the sense of satiety derived from a fatty meal requires knowledge of the various interactions between the gut and the brain (2,22,40). One of the main satiety mechanisms triggered by ingestion of fat is the release of...
Substantial water fluxes across the small intestine occur during digestion of food, but so far measuring these has required invasive intubation techniques. This paper describes a non-invasive magnetic resonance imaging (MRI) technique for measuring small bowel water content which has been validated using naso-duodenal infusion. Eighteen healthy volunteers were intubated, with the tube position being verified by MRI. After a baseline MRI scan, each volunteer had eight 40 ml boluses of a non-absorbable mannitol and saline solution infused into their proximal small bowel with an MRI scan being acquired after each bolus. The MRI sequence used was an adapted magnetic resonance cholangiopancreatography sequence. The image data were thresholded to allow for intra- and inter-subject signal variations. The MRI measured volumes were then compared to the known infused volumes. This MRI technique gave excellent images of the small bowel, which closely resemble those obtained using conventional radiology with barium contrast. The mean difference between the measured MRI volumes and infused volumes was 2% with a standard deviation of 10%. The maximum 95% limits of agreement between observers were -15% to +17% while measurements by the same operator on separate occasions differed by only 4%. This new technique can now be applied to study alterations in small bowel fluid absorption and secretion due to gastrointestinal disease or drug intervention.
Patients with symptomatic diverticular disease exhibit visceral hypersensitivity, and this may be mediated by ongoing low grade inflammation and upregulation of tachykinins.
Fat is often included in common foods as an emulsion of dispersed oil droplets to enhance the organoleptic quality and stability. The intragastric acid stability of emulsified fat may impact on gastric emptying, satiety and plasma lipid absorption. The aim of the present study was to investigate whether, compared with an acid-unstable emulsion, an acid-stable fat emulsion would empty from the stomach more slowly, cause more rapid plasma lipid absorption and cause greater satiety. Eleven healthy male volunteers received on two separate occasions 500 ml of 15 % (w/w) [ 13 C]palmitate-enriched olive oil-in-water emulsion meals which were either stable or unstable in the acid gastric environment. MRI was used to measure gastric emptying and the intragastric oil fraction of the meals. Blood sampling was used to measure plasma lipids and visual analogue scales were used to assess satiety. The acid-unstable fat emulsion broke and rapidly layered in the stomach. Gastric emptying of meal volume was slower for the acid-stable fat emulsion (P,0·0001; two-way ANOVA). The rate of energy delivery of fat from the stomach to the duodenum was not different up to t ¼ 110 min. The acid-stable emulsion induced increased fullness (P,0·05), decreased hunger (P, 0·0002), decreased appetite (P,0·0001) and increased the concentration of palmitic acid tracer in the chylomicron fraction (P,0·04). This shows that it is possible to delay gastric emptying and increase satiety by stabilising the intragastric distribution of fat emulsions against the gastric acid environment. This could have implications for the design of novel foods. Magnetic resonance imaging: Echo-planar imaging: Stomach: Human studiesThe current epidemic of obesity in the Western population (1) can be related at least in part to the increasing consumption of pre-processed food that is high in added fat. The inclusion of fat impacts significantly upon both the palatability and the stability of common foodstuffs. The most common method of including fat is as an emulsion of finely dispersed oil droplets. This emulsion will enhance both the mouth-feel and stability of the food, for example, by changing the viscoelastic properties which gives rise to a perception of creaminess (2) . Furthermore the oil droplets can also be the principal carrier of aroma components and determine the rate of aroma release (3,4) during the process of eating. Once eaten, the presence of the emulsion within the food will impact upon the gastrointestinal response (5 -7) . Thus the presence of fat and the form of fat within a food impacts upon all aspects of a consumer's experience of that food from mouth-feel through to metabolism. Reducing the fat content of food whilst maintaining consumer satisfaction is not straightforward and it requires a good understanding of the relationship between food structure and its behaviour before and during digestion.The physical state and the spatial distribution of fat within the gastric lumen during digestion are critical factors influencing the rate of fat deliv...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.