A research group led by Associate Professor Hiroshi Yamada of the Faculty of Medicine and Health Sciences at the University of Tsukuba has succeeded in quantitatively measuring whether or not eating dry food makes you thirsty.
We feel thirsty when we eat foods with little moisture, such as rice crackers or cookies, and we also feel thirsty when we eat foods that are high in salt, such as herring roe. These feelings of thirst and hunger are subjective sensations generated by the brain, but do thirst and hunger actually occur in our bodies in the way that we sense them?
In this study, we developed a method to quantify thirst by measuring the physiological changes that occur in the body when eating dry food. It is known that the sensation of thirst correlates well with the osmotic pressure of the blood. It is also known that the degree of hunger is well reflected by ghrelin, a hormone secreted from the stomach. Therefore, using macaque monkeys (Japanese macaques and rhesus monkeys), which are laboratory animals that are closest to humans and can regulate their eating and drinking habits, we measured the changes in blood osmotic pressure and ghrelin before and after eating dry crackers (solid food such as hardtack).
As a result, it was confirmed that blood osmolality increased in all four monkeys after eating the crackers, reflecting thirst. In addition, ghrelin decreased in three of the four monkeys after eating the crackers, reflecting abdominal fullness. These indices showed changes that were in good agreement with the amount of water and food consumed by the monkeys, indicating that changes in the degree of thirst and hunger can be quantified by measuring osmolality and ghrelin.
The results of this research are expected to be used not only to maintain health, but also to evaluate diseases related to abnormalities in desires such as thirst and hunger (depression, polydipsia, bulimia, etc.).
Paper information:[eNeuro] A Method for Evaluating Hunger and Thirst in Monkeys by Measuring Blood Ghrelin and Osmolality Levels
