Static in vitro digestion model adapted to the general older adult population: an INFOGEST international consensus.

Understanding the mechanisms of food digestion is of paramount importance to determine the effect foods have on human health. Significant knowledge on the fate of food during digestion has been generated in healthy adults due to the development of physiologically-relevant in vitro digestion models. However, it appears that the performance of the oro-gastrointestinal tract is affected by ageing and that a model simulating the digestive conditions found in a younger adult (<65 years) is not relevant for an older adult (>65 years). The objectives of the present paper were: (1) to conduct an exhaustive literature search to find data on the physiological parameters of the older adult oro-gastrointestinal tract, (2) to define the parameters of an in vitro digestion model adapted to the older adult. International experts have discussed all the parameters during a dedicated workshop organized within the INFOGEST network. Data on food bolus properties collected in the older adult were gathered, including food particle size found in older adult boluses. In the stomach and small intestine, data suggest that significant physiological changes are observed between younger and older adults. In the latter, the rate of gastric emptying is slowed down, the pH of the stomach content is higher, the amount of secretions and thus the hydrolytic activities of gastric and intestinal digestive enzymes are reduced and the concentration of bile salts lower. The consensus in vitro digestion model of the older adult proposed here will allow significant progress to be made in understanding the fate of food in this specific population, facilitating the development of foods adapted to their nutritional needs. Nevertheless, better foundational data when available and further refinement of the parameters will be needed to implement the proposed model in the future.

Characterization of raft-forming alginate suspensions formed in HCl or model food systems at varying pH levels to better simulate gastric postprandial conditions.

OBJECTIVE: Elucidate properties of raft-forming alginates in vitro with varying composition, a system in which the raft was formed (HCl solution; tomato soup; protein-rich beverage), and pH levels for a more accurate representation of postprandial gastric conditions. SIGNIFICANCE: Knowledge of the impact of the food system and pH on properties of raft-forming alginates may aid in formulation optimization. Recommendations may be made on food that is consumed prior to their consumption to optimize efficacy as a therapeutic agent. METHODS: Dispersions of sodium alginate, calcium carbonate, and sodium bicarbonate were prepared with levels similar to commercial formulations. Rafts were formed in HCl solution, tomato soup, and a protein-rich beverage at pH 1-4 to assess raft properties. RESULTS: Significant differences (p < 0.05) in raft mass, strength, resilience, and ability to buffer acid were observed depending on the system in which the rafts were formed. The highest mass was obtained in tomato soup (48.5 ± 9.8 g) compared to the protein-rich beverage and HCl solution (32.5 ± 4.5 g and 23.4 ± 4.8 g, respectively) at pH 1. Rafts formed in the protein-rich beverage exhibited the highest strength. Rafts formed in both food systems had a greater ability to buffer added acid compared to rafts formed in HCl solution. CONCLUSIONS: In vitro testing of raft forming alginates in HCl solution at low pH may not be sufficient to describe in vivo events, as a strong matrix effect was observed when rafts were formed in model meal systems at representative postprandial pH levels.

Can dynamic in vitro digestion systems mimic the physiological reality?

During the last decade, there has been a growing interest in understanding the fate of food during digestion in the gastrointestinal tract in order to strengthen the possible effects of food on human health. Ideally, food digestion should be studied in vivo on humans but this is not always ethically and financially possible. Therefore simple static in vitro digestion models mimicking the gastrointestinal tract have been proposed as alternatives to in vivo experiments but these models are quite basic and hardly recreate the complexity of the digestive tract. In contrast, dynamic models that allow pH regulation, flow of the food and injection in real time of digestive enzymes in the different compartments of the gastrointestinal tract are more promising to accurately mimic the digestive process. Most of the systems developed so far have been compared for their performances to in vivo data obtained on animals and/or humans. The objective of this article is to review the validation towards in vivo data of some of the dynamic digestion systems currently available in order to determine what aspects of food digestion they are able to mimic. Eight dynamic digestion systems are presented as well as their validation towards in vivo data. Advantages and limits of each simulator is discussed. This is the result of a cooperative international effort made by some of the scientists involved in Infogest, an international network on food digestion.