Water is an essential nutrient.1-3 Water is the main component of cells, tissues, and organs and accounts for 50 %‒70 % of a young adult’s body weight.1,4-6 For example, a 70 kg human contains 42 liters of total body water, of which 28 liters are intracellular water and 14 liters are extracellular fluids.1,4-7 In general, water consumption is regulated by thirst.1,4 According to experts, humans consume 20 % to 30 % of water in the form of solid food, while 70 % to 80 % comes fromdrinks, depending on the food choice and type of drink.1,4,8 Current guidelines recommend that sedentary adults drink an average of 2 liters of water per day.1,2,4 Total body water weight varies throughout life and is essential for cellular homeostasis (the ability of cells to keep the organism in constant balance even in the face of external fluctuations).