Water physiology: Essentiality, metabolism, and health implications

Water is the most abundant molecule in the human body that undergoes continuous recycling. Numerous functions have been recognized for body water, including its function as a solvent, as a means to remove metabolic heat, and as a regulator of cell volume and overall function. Tight control mechanisms have evolved for precise control of fluid balance, indicative of its biological importance. However, water is frequently overlooked as a nutrient. This article reviews the basic elements of water physiology in relation to health, placing emphasis on the assessment of water requirements and fluid balance. Current recommendations are also discussed.