Water is essential for survival, but one in three individuals worldwide (2.2 billion people) lacks access to safe drinking water. Water intake requirements largely reflect water turnover (WT), the water used by the body each day. We investigated the determinants of human WT in 5604 people from the ages of 8 days to 96 years from 23 countries using isotope-tracking ( 2H) methods. Age, body size, and composition were significantly associated with WT, as were physical activity, athletic status, pregnancy, socioeconomic status, and environmental characteristics (latitude, altitude, air temperature, and humidity). People who lived in countries with a low human development index (HDI) had higher WT than people in high-HDI countries. On the basis of this extensive dataset, we provide equations to predict human WT in relation to anthropometric, economic, and environmental factors.
Bibliographical noteAcknowledgments: We thank the International Atomic Energy Agency (IAEA), Taiyo Nippon Sanso, and SERCON for their support and T. Oono for his tremendous efforts at fundraising on our behalf. Y.Y., T.Y., and M.M. thank K. Abe for his support. Y.Y. and M.K. would like to pay gratitude and respect to their mentor, T. Morimoto, an emeritus professor of the Department of Physiology, Kyoto Prefectural University of Medicine, who passed away in July 2019.
Funding: The IAEA DLW Database is generously supported by the IAEA, Taiyo Nippon Sanso, and SERCON. The authors also gratefully acknowledge funding support for the database from the US National Science Foundation (grant BCS-1824466 to H.P.) and the Chinese Academy of Sciences (CAS grant 153E11KYSB20190045 to J.R.S.). The funders played no role in the content of this manuscript.
Data Availability StatementAll data used in these analyses are freely available on the IAEA DLW Database, which can be found at https://doubly-labelled-water-database.iaea.org/home or www.dlwdatabase.org.
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