Are you drinking enough?  How much water to drink in a day is something many people don’t keep track of, but especially in the hot summer weather it is important to keep yourself well-hydrated.

Water composes over half of the human body, and is essential in vital functions such as regulating body temperature, digestion and circulation, and cushioning vital organs.  In normal daily functioning we lose about two litres of water, mostly through urination and perspiration.  Eight cups of water per day simply replaces this loss, although any drinks as well as some foods such as cucumber or soup also help to rehydrate.  Water loss increases with exercise and in hot environments, as well as at higher altitudes, so more water replacement is needed in these situations.  When being active in the summer months, it is important to replace the extra water you are losing through perspiration and increased activity.

There have been conflicting opinions on how much water one should drink when exercising, ranging from the old idea that athletes should not drink at all during exercise, to the other extreme that you can’t drink enough.  It is possible to drink too much water, resulting in a state of low blood sodium called hyponatremia, but this seldom occurs beyond extreme situations, usually involving marathon runners.  For typical people and moderate athletes, the general rule of thumb is to drink when thirsty, but to be aware of when you do become thirsty and not ignore your body’s signal.

For up to an hour of even intense exercise, drinking should match what is lost with sweating.  This can be, for example, 1.6 litres for a game of summer tennis, although 600-800 mL is typical.  If exercising more than an hour, the body may need  carbohydrates and salt, so sports drinks or diluted fruit juices are recommended to replenish supplies and aid water absorption.  Beverages with too much sugar, or with caffeine or alcohol will only increase dehydration, so should be avoided with exercise.  Signs of dehydration include headache, physical and mental sluggishness, dry mouth and eyes, and dark yellow (or lack of any) urine.  If let to go on unabated, dehydration can cause overheating, leading to heat cramps, heat exhaustion, and even life-threatening heatstroke.

To keep yourself well-hydrated this summer, drink water regularly throughout the day, with every meal, and not only during, but an hour or two before exercise.  Also, continue drinking for four to six hours after exercise to account for ongoing sweat and urinary losses.  If you find water too boring, lightly flavouring it with a powder or some lemon may make it more palatable.  Whether or not to use hard-plastic bottles or bottled water is a separate and involved topic, but in general cool tap water kept on hand and consumed when thirsty is your best bet for keeping properly hydrated this summer.