Alterations of Sensory Perceptions in Healthy Elderly Subjects during Fasting and Refeeding. A pilot study.

International audienceBackground: Sensory perception losses may contribute to age-related malnutrition by affecting food selection and consumption.Objective: To determine the effects of a 36-hour fast followed by a 6-hour refeeding period on sensory perceptions in 7 healthy elderly subjects (65-80 years of age) and 6 healthy young subjects (18-35 years of age).Methods: Self-perceived hunger and olfactory ratings were recorded on visual analogue scales in response to three different classes of odorant stimuli (salt, sweet and sour). Odorant stimuli were administered three times during the study, twice during the fasting period (12 and 24 h fasted) and once at the end of the re-nutrition period.Results: A significant difference was found between the two groups for the self-perceived hunger ratings in response to the sour stimuli. A significant difference was observed between the two groups for olfactory ratings as regards the salt and sour odorant stimuli. Among the metabolic changes associated with fasting and refeeding, blood glucose was significantly related (r(2) = 0.97, p = 0.001) to the perception of hunger in the control group subjects, but no such relationship was found for the elderly subjects (r(2) = 0.16, p = NS).Conclusion: (1) Self-perceived hunger and olfactory ratings are specifically affected in healthy elderly. (2) Nutritional status can modulate sensory perceptions in elderly and young during the transition from fasting to refeeding

Slow and fast dietary proteins differently modulate postprandial protein accretion

The speed of absorption of dietary amino acids by the gut varies according to the type of ingested dietary protein. This could affect postprandial protein synthesis, breakdown, and deposition. To test this hypothesis, two intrinsically (13)C-leucine-labeled milk proteins, casein (CAS) and whey protein (WP), of different physicochemical properties were ingested as one single meal by healthy adults. Postprandial whole body leucine kinetics were assessed by using a dual tracer methodology. WP induced a dramatic but short increase of plasma amino acids. CAS induced a prolonged plateau of moderate hyperaminoacidemia, probably because of a slow gastric emptying. Whole body protein breakdown was inhibited by 34% after CAS ingestion but not after WP ingestion. Postprandial protein synthesis was stimulated by 68% with the WP meal and to a lesser extent (+31%) with the CAS meal. Postprandial whole body leucine oxidation over 7 h was lower with CAS (272 ± 91 μmol⋅kg(−1)) than with WP (373 ± 56 μmol⋅kg(−1)). Leucine intake was identical in both meals (380 μmol⋅kg(−1)). Therefore, net leucine balance over the 7 h after the meal was more positive with CAS than with WP (P < 0.05, WP vs. CAS). In conclusion, the speed of protein digestion and amino acid absorption from the gut has a major effect on whole body protein anabolism after one single meal. By analogy with carbohydrate metabolism, slow and fast proteins modulate the postprandial metabolic response, a concept to be applied to wasting situations