The human body is 45-60% water, so it is obviously important! Water has multiple biological functions, including regulating body temperature, flushing out waste products from the liver and kidneys, lubricating joints, and carrying nutrients and oxygen to the body’s cells. We lose water each day via sweat, urine, feces, and exhaling, therefore it needs to be replaced. If the output of fluid exceeds the input, dehydration will result.

Dehydration can also occur when the body’s fluid and electrolyte balance mechanisms fail. This may be due to diarrhea, vomiting, fever, climate variations, and excessive exercise or urination due to uncontrolled diabetes or diuretic treatment, for example.

Some unpleasant symptoms of dehydration are headaches, fatigue, nausea, and dry mouth. Severe dehydration can cause confusion, impaired vision, kidney and liver failure, and loss of consciousness. Unfortunately, dehydration can occur without symptoms, or the feeling of thirst can be mistaken for hunger, therefore we need to be conscious of how much fluid we are consuming.

How much water or fluid one requires depends on sex, age, weight, activity levels, and environment, among other factors. But general recommendations are 11 ½ cups a day for women, and 15 ½ cups for men. Good news! Caffeinated beverages like coffee, tea, and cola, although perhaps not the ideal choices (READ: you might want to skip the mocha latte), do count as hydrating beverages. The only drinks that are not considered hydrating are those that contain alcohol.

More good news! Approximately 20% of the water we consume comes from food, predominantly fruits and vegetables. Among the hydrating superstars are watermelon, cucumbers, zucchini, celery, tomatoes, and strawberries. Fortunately these are all in-season during the summer months, when we typically need the most water.

A word of caution: there is such a thing as drinking too much water. An excess of fluid in the body dilutes the blood concentration of sodium - this is termed hyponatremia and causes headaches, confusion, nausea, muscle cramps, fatigue, and in severe cases, seizures and loss of consciousness. It most commonly occurs in athletes who participate in prolonged, intense exercise, who therefore are drinking a lot of water and losing sodium via sweat, and individuals with chronic health conditions that prevent proper elimination of fluid, such as congestive heart failure and end stage renal failure. For an illness that requires a fluid restriction, or a limited fluid allotment, the appropriate quantity to drink should be prescribed by a physician. And for those who engage in vigorous exercise lasting more than an hour, sport drinks containing electrolytes are recommended to hydrate while replacing minerals lost with sweat.