The total body water of adults accounts for approximately 60% of body weight, and dehydration has been reported to increase the risk of adverse health outcomes such as cardiovascular events, impaired kidney function, and cognitive decline¹. In addition, with the recent increase in extremely hot days, the number of patients transported for heat-related illness, particularly among older adults, has been rising. As a result, appropriate hydration management that takes into account age and environmental changes has become an urgent public health issue.
Water turnover (WT) refers to the total amount of water entering and leaving the human body per day, that is, water intake from beverages and foods and water loss through urine, sweat, and other routes, and is used as an indicator of hydration status. Previous research by Professor Yosuke Yamada and colleagues has shown that approximately 40% of the variation in human WT can be explained by intrinsic and extrinsic factors such as sex, body weight, physical activity level, air temperature, humidity, and altitude². However, the remaining approximately 60% of determinants, as well as the direct relationships between WT and health outcomes serving as conditioning indicators, have not yet been fully elucidated.
In this study, WT will be measured in community residents and analyzed in relation to various health outcomes. Furthermore, by developing a simplified predictive model of WT that reflects characteristics of Japanese populations, the study aims to establish a scientific foundation for personalized hydration management and to generate insights that contribute to health maintenance.

■ Study Overview

Participants : Approximately 3,000 adult men and women aged 18 to 90 years residing in Miyagi Prefecture

Methods : Water turnover (WT) will be measured using the stable isotope-labeled water method. In addition, hydration-related biomarkers (such as blood and urine parameters), body composition, and lifestyle-related health indicators will be assessed, and their relationships with WT will be analyzed.

Study Period : April 2026 to March 2029(Measurements will begin in August 2026)

■ Research on Water Turnover at Tohoku University

A research group led by Professor Yosuke Yamada at the Graduate School of Biomedical Engineering, Tohoku University, conducted a large-scale study involving 5,604 individuals, from 8-day-old infants to 96-year-old adults, across 23 countries.
The study established a predictive equation for daily water turnover, that is, water influx and efflux in the human body, and the findings were published in Science in November 2022.
In addition, Professor Yamada has conducted extensive research in this field, including work titled "Elucidation of factors influencing water and energy metabolism across the human lifespan," for which he received the FY2024 Japan Society for the Promotion of Science (JSPS) Prize.


■Research and Development in Otsuka Pharmaceutical's Nutraceutical Business

In its nutraceutical business, Otsuka Pharmaceutical leverages the expertise cultivated through its pharmaceutical business to advance the maintenance and improvement of people's health and overall societal well-being. The company is engaged in the research and development of unique, science-based products that contribute to addressing both health-related and societal challenges.
Currently, research and development related to beverages and foods is conducted at the Nutraceutical Research Institute (Saga Research Site and Otsu Research Site) and the Advanced Research Institute.

Based on the corporate philosophy of 'Otsuka-people creating new products for better health worldwide,' Otsuka Pharmaceutical continues to contribute to the health and well-being of people around the world.