This allows the kidneys to release excess water, and preserve water balance. When fluid is consumed, osmoreceptors in the mouth are stimulated, which reduces AVP secretion.
Despite popular myths, coffee can be considered a source of fluid ( 7, 25), and although alcohol may increase fluid losses short-term, it is not believed to result in significant water loss over a day’s time ( 25). In a typical sedentary adult, this represents ~7 cups (1575mL) from beverages, ~3 cups (675mL) from foods, and ~1 cup (300mL) from normal metabolic processes ( 27). Typically, plasma osmolality is tightly maintained between 280–290mOsm/kg however, an increase of approximately 1–3% creates a drive to drink ( 12, 43).įluid water intake generally accounts for ~70–80% of total water consumed ( 25), and ~20–30% of total water intake comes from solid foods ( 5, 19, 25). The thirst sensation is triggered with a body water loss of 1–2% a range where physical and cognitive performance may decline ( 4, 9, 21, 22, 25, 34, 38). social, cultural, behavioral) factors that influence water intake ( 25, 35, 43) and fluid balance. osmoreceptors in the brain and mouth, baroreceptors in blood vessels and atrium) and non-regulated (e.g. There are regulated or physiological (e.g. Water input comes from food and beverage ingestion, and normal metabolic processes ( Figure 1). Total water output is estimated to be approximately 1500–3100mL/d for adults in temperate climates ( 19, 25). Gastrointestinal and fecal water output accounts for 100–300mL/d ( 19, 25, 27). Urine output generally ranges 1000–2000mL/d, but can be altered by exercise and heat strain ( 25). On average insensible water losses are about 450mL/d however, during vigorous physical activity in a hot environment, losses in excess of 3L/hr are possible ( 37).
clothing worn, sweat rate) ( 19, 25, 38). wind speed, humidity, and sun exposure), activity level, body composition, degree of physical fitness, and other variables (e.g. Insensible water loss, which includes sweat loss, can vary with environmental conditions (i.e. Respiratory water loss averages 250–350mL/d in sedentary adults however, physical activity can increase losses to about 600mL/d ( 19, 25). increased urine output in colder climates, decreased urine output in hot climates and greater water loss via sweat with longer duration activities) ( 25). Environmental factors (e.g., humidity, temperature) and intensity and duration of physical activity also impact urine output (e.g. The skin, kidneys, lungs, and digestive system are all sources of water output ( Figure 1).
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