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Dry food intake can increase thirst, and this sensation is difficult to quantify. Researchers at University of Tsukuba has developed a method that measures and quantifies the physiological changes occurring in the body during dry food consumption. This method might significantly contribute to health maintenance and the evaluation of diseases related to abnormal cravings, such as polydipsia and polyphagia.

Tsukuba, Japan—Consuming foods with low water content, such as rice crackers and cookies, often leads to increased thirst. While thirst and hunger are subjective sensations produced by the brain, they are caused by various factors. For instance, eating cookies can dry out your mouth, prompting a desire for tea; salt intake can also make one thirsty. These eating and drinking decisions are regulated by our body's condition. However, do the sensations of thirst and hunger align with the body's physiological changes?

In this study, researchers quantitatively measured and evaluated whether eating dry foods triggers thirst sensation in macaque monkeys (Japanese macaque and rhesus macaque), which are laboratory animals capable of regulating eating and drinking and are closely related to humans. Thirst sensation correlates well with blood osmolality, and hunger is well reflected by ghrelin, a hormone secreted from the stomach. Therefore, the researchers collected blood samples and measured osmolality and ghrelin alterations before and after feeding the macaque monkeys with dry crackers (a type of dry bread), which they consumed daily. Results showed that changes in blood osmolality and ghrelin levels corresponded well with the degree of thirst and hunger, suggesting that thirst resulting from dry food consumption can be quantified.

These findings are potentially useful for maintaining health but evaluating diseases related to abnormal cravings, such as excessive thirst and hunger (e.g., depression, polydipsia, and bulimia).

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This study was supported by the Japan Society for the Promotion of Science KAKENHI (Grant Number JP19H05007) and Moonshot Research and Development JPMJMS2294 (H.Y.).

Original Paper

Title of original paper:

A Method for Evaluating Hunger and Thirst in Monkeys by Measuring Blood Ghrelin and Osmolality Levels

Journal:

eNeuro

DOI:

10.1523/ENEURO.0481-23.2024

Correspondence

Associate Professor YAMADA Hiroshi
Institute of Medicine, University of Tsukuba

Related Link

Institute of Medicine