THE ROLE OF THE ILEUM IN FOOD INTAKE REGULATION

Ileal fat receptors, with other gastrointestinal receptors, may play a role in the development of postprandial satiety by affecting gastric emptying.     

Health effects of resistant starch

The merits of a fibre‐rich diet are well documented. Resistant starch (RS) is a form of starch that resists digestion in the small intestine and, as such, is classified as a type of dietary fibre. RS can be categorised as one of five types (RS1–5), some of which occur naturally in foods such as bananas, potatoes, grains and legumes and some of which are produced or modified commercially, and incorporated into food products. This review describes human evidence on the health effects of RS consumption, with the aim of identifying any benefits of RS‐rich foods and RS as a functional ingredient. The reduced glycaemic response consistently reported with RS consumption, when compared with digestible carbohydrate, has resulted in an approved European Union health claim. Thus, RS‐rich foods may be particularly useful for managing diabetes. There appears to be little impact of RS on other metabolic markers, such as blood pressure and plasma lipids, though data are comparatively limited. Promising results on markers of gut health suggest that further research may lead to the classification of RS as a prebiotic. Microbial fermentation of RS in the large intestine to produce short‐chain fatty acids likely underpins some of its biological effects, including increasing satiety. However, effects on appetite have not resulted in notable changes in bodyweight after long‐term consumption. Emerging research suggests potential for RS as an ingredient in oral rehydration solutions and in the treatment of chronic kidney disease. Overall, RS possesses positive properties as a healthy food component.     

Hunger Modulates the Responses to Gustatory Stimuli of Single Neurons in the Caudolateral Orbitofrontal Cortex of the Macaque Monkey

1. In order to determine whether the responsiveness of neurons in the caudolateral orbitofrontal cortex (a secondary cortical gustatory area) is influenced by hunger, the activity evoked by prototypical taste stimuli (glucose, NaCl, HCl, and quinine hydrochloride) and fruit juice was recorded in single neurons in this cortical area before, while, and after cynomolgous macaque monkeys were fed to satiety with glucose or fruit juice. 2. It was found that the responses of the neurons to the taste of the glucose decreased to zero while the monkey ate it to satiety during the course of which his behaviour turned from avid acceptance to active rejection. 3. This modulation of responsiveness of the gustatory responses of the neurons to satiety was not due to peripheral adaptation in the gustatory system or to altered efficacy of gustatory stimulation after satiety was reached, because modulation of neuronal responsiveness by satiety was not seen at earlier stages of the gustatory system, including the nucleus of the solitary tract, the frontal opercular taste cortex, and the insular taste cortex. 4. The decreases in the responsiveness of the neurons were relatively specific to the food with which the monkey had been fed to satiety. For example, in seven experiments in which the monkey was fed glucose solution, neuronal responsiveness decreased to the taste of the glucose but not to the taste of blackcurrant juice. Conversely, in two experiments in which the monkey was fed to satiety with fruit juice, the responses of the neurons decreased to fruit juice but not to glucose. 5. These and earlier findings lead to a proposed neurophysiological mechanism for sensory-specific satiety in which the information coded by single neurons in the gustatory system becomes more specific through the processing stages consisting of the nucleus of the solitary tract, the taste thalamus, and the frontal opercular and insular taste primary taste cortices, until neuronal responses become relatively specific for the food tasted in the caudolateral orbitofrontal cortex (secondary) taste area. Then sensory-specific satiety occurs because in this caudolateral orbitofrontal cortex taste area (but not earlier in the taste system) it is a property of the synapses that repeated stimulation results in a decreased neuronal response. 6. Evidence was obtained that gustatory processing involved in thirst also becomes interfaced to motivation in the caudolateral orbitofrontal cortex taste projection area, in that neuronal responses here to water were decreased to zero while water was drunk until satiety was produced.     

Plasma cholecystokinin levels in Prader‐Willi syndrome and obese subjects

The cardinal feature of individuals with Prader‐Willi syndrome (PWS) is severe hyperphagia‐mediated obesity resulting from a faulty satiety mechanism. PWS is the most common genetic cause of marked obesity. Cholecystokinin (CCK) is a 33‐amino‐acid peptide found in high levels in the gut and brain involved in mediating the satiety response to meals. Free fatty acids (FFA) are responsible for the stimulation of CCK release after a fatty meal, and CCK and plasma FFA levels rise in tandem in normal individuals. Fasting plasma CCK levels were measured by radio‐immunoassay in 33 PWS subjects with a mean age of 22.2 years ± 8.1 years and 24 obese control subjects without a known cause of their obesity with a mean age of 28.7 years ± 12.9 years. Consistent with previous findings, neither fasting plasma FFA levels (617.5 versus 486.8 μm/mL) or CCK levels (21.0 versus 19.1 pg/mL) were significantly different in PWS or control subjects, respectively. However, there was a significant correlation between fasting plasma FFA and CCK levels in obese subjects (r = 0.64, P < 0.01), this correlation was completely lacking in PWS subjects (r = −0.06, P = 0.79). This difference in correlation coefficients constitutes a large effect. There were no significant effects observed for genetic subtypes (15q11‐q13 deletion or maternal disomy 15), body mass index, percentage of fat, plasma levels of insulin, C‐peptide, glucagon or leptin, age, or gender on CCK levels in our PWS subjects. These results suggest that differences in the peripheral CCK response to FFA levels may be a factor contributing to the altered satiety response in PWS subjects. Am. J. Med. Genet. 95:67–70, 2000. © 2000 Wiley‐Liss, Inc.     

Variety enhances food intake in humans: Role of sensory-specific satiety

Twenty-one subjects were studied to evaluate the effect of renewal of sensory stimulations of previously eaten foods on sensory-specific satiety and intake. The subjects ate French fries then brownie cakes ad libitum in three situations: “monotonous” — fries then brownies were consumed alone; “simultaneous” — condiments (ketchup and mayonnaise for the fries, vanilla cream and whipped cream for the brownies) were added during intakes; “successive” — after intake of fries alone, ketchup then mayonnaise were available with fries and, after intake of brownies alone, vanilla cream then whipped cream were offered with brownies. The quantities eaten in the “simultaneous” and “successive” situations were higher (p < 0.001) than those in the “monotonous” one (1485 ± 582 and 1682 ± 777 kcal vs 1195 ± 552 kcal, respectively). In the “successive” situation, hedonic ratings for fries diminished during intake but increased after the introduction of ketchup, leading to additional intake of fries. Similarly, hedonic ratings for brownies diminished during intake and increased after the introduction of vanilla cream leading to additional brownie intake (mayonnaise and whipped cream had no significant effect). Food variety, obtained by adding condiments can increase food intake in the short term. The mechanism by which food consumption is increased after the addition of condiments is introduced is at least partly related to the attenuation of sensory-satiety for a given food.     

Food texture and the satiety cascade

Using the satiety cascade model as a framework, this paper describes how food texture can influence the strength and duration of sensory, cognitive and post‐ingestive signals that determine when a meal ends (satiation) and the inhibition of appetite between meals (satiety). The influence of food texture on oro‐sensory exposure time, expectations about the satiating effect of a food and processing of food in the gastrointestinal system is considered, as well how the interaction of these processes may impact on the overall experience of satiety. This body of work suggests that texture is one element of a food's flavour profile which could be a candidate for manipulation in the development of ‘high‐satiety’ foods.     

Gastrointestinal Nutrient Infusion Site and Eating Behavior: Evidence for A Proximal to Distal Gradient within the Small Intestine?

The rapidly increasing prevalence of overweight and obesity demands new strategies focusing on prevention and treatment of this significant health care problem. In the search for new and effective therapeutic modalities for overweight subjects, the gastrointestinal (GI) tract is increasingly considered as an attractive target for medical and food-based strategies. The entry of nutrients into the small intestine activates so-called intestinal “brakes”, negative feedback mechanisms that influence not only functions of more proximal parts of the GI tract but also satiety and food intake. Recent evidence suggests that all three macronutrients (protein, fat, and carbohydrates) are able to activate the intestinal brake, although to a different extent and by different mechanisms of action. This review provides a detailed overview of the current evidence for intestinal brake activation of the three macronutrients and their effects on GI function, satiety, and food intake. In addition, these effects appear to depend on region and length of infusion in the small intestine. A recommendation for a therapeutic approach is provided, based on the observed differences between intestinal brake activation.     

Effects of ingesting low glycemic index carbohydrate food for the sahur meal on subjective,metabolic and physiological responses,and endurance performance in Ramadan fasted men

Purpose: To investigate the effect of low glycemic index (LGI) carbohydrate meal on subjective, metabolic and physiological responses, and endurance performance in the Ramadan fasted state. Methods: During Ramadan, 12 Muslim men, in a randomized and crossover design, ingested for the sahur meal (i.e. last meal before commencement of the day’s fast), either LGI (glycemic index?=?37) or mixed (CON; ～57) meal of equivalent macro-nutrient. At ～12?h post-prandial, subjects completed a 60?min continuous run. Results: There were no significant differences between the two meals for ratings in perceived satiety, fullness, appetite and mood states. During steady-state exercise, there were no significant differences in metabolic and physiological measures. In the time-trial, distance ran was significantly lower in LGI versus CON meal trial, but with a corresponding lower perceived exertion in the LGI trial. Conclusion: Compared to CON, ingesting LGI as the sahur meal did not provide any metabolic, physiological or performance benefits during endurance run performed 12?h post-prandial in Ramadan fasted state.     

Effect of interleukin-2 on some micronutrients during adoptive immunotherapy for various cancers.

In 20 patients, we investigated the effect of interleukin-2 (IL-2) treatment during adoptive immunotherapy for various cancers on circulating levels of: thiamin; biotin; folate; pantothenate; riboflavin; nicotinate; vitamins A, B6, B12 and E; carotenes; free and total cholines; inositol; and free and total carnitines. Of the above micronutrients, only vitamins A, B6, B12, inositol, carotenes and folate varied markedly from normal levels (pre IL-2 exposure) to abnormal levels (post IL-2). Following IL-2 exposure, every patient's B12 level was significantly elevated; 50% of the levels were abnormally increased above 1000 pg/ml. Extreme significant elevations of inositol were also seen in 90% of the patients. In contrast, IL-2 exposure depressed normal vitamins A, B6, carotene, and folate levels to subnormal; 90% of the patients became B6 hypovitaminemic; 60% for vitamin A, 80% for carotene, and 45% for folate. Other micronutrients tested showed no clear deviations from normal levels post IL-2 exposure. Some reasons for micronutrient variations are discussed.