<P> Profuse sweating can increase the need for electrolyte replacement . Water - electrolyte imbalance produces headache and fatigue if mild; illness if moderate, and sometimes even death if severe . For example, water intoxication (which results in hyponatremia), the process of consuming too much water too quickly, can be fatal . Deficits to body water result in volume contraction and dehydration . Diarrhea is a threat to both body water volume and electrolyte levels, which is why diseases that cause diarrhea are great threats to fluid balance . </P> <P> The amount of water varies with the individual, as it depends on the condition of the subject, the amount of physical exercise, and on the environmental temperature and humidity . In the US, the reference daily intake (RDI) for water is 3.7 litres per day (l / day) for human males older than 18, and 2.7 l / day for human females older than 18 including water contained in food, beverages, and drinking water . The common misconception that everyone should drink two litres (68 ounces, or about eight 8 - oz glasses) of water per day is not supported by scientific research . Various reviews of all the scientific literature on the topic performed in 2002 and 2008 could not find any solid scientific evidence that recommended drinking eight glasses of water per day . For example, people in hotter climates will require greater water intake than those in cooler climates . An individual's thirst provides a better guide for how much water they require rather than a specific, fixed number . A more flexible guideline is that a normal person should urinate 4 times per day, and the urine should be a light yellow color . </P> <P> A constant supply is needed to replenish the fluids lost through normal physiological activities, such as respiration, perspiration and urination . Food contributes 0.5 to 1 l / day, and the metabolism of protein, fat, and carbohydrates produces another 0.25 to 0.4 l / day, which means that 2 to 3 l / day of water for men and 1 to 2 l / day of water for women should be consumed as fluid to meet the Recommended Daily Intake (RDI). </P> <P> In terms of mineral nutrients intake, it is unclear what the drinking water contribution is . However, inorganic minerals generally enter surface water and ground water via storm water runoff or through the Earth's crust . Treatment processes also lead to the presence of some minerals . Examples include calcium, zinc, manganese, phosphate, fluoride and sodium compounds . Water generated from the biochemical metabolism of nutrients provides a significant proportion of the daily water requirements for some arthropods and desert animals, but provides only a small fraction of a human's necessary intake . </P>

Explain how the body gains and loses body fluids