The amount of water that you need to have the optimal sort of concentrations of things is determined by how much urine your kidneys produce and how much they excrete each day.

为了保持体内物质的理想浓度,所需的水量,取决于肾脏每天产生,以及排出体外的尿量

耶鲁公开课 - 生物医学工程探索课程节选