Water Intake

Do you need to drink six to eight glasses of water a day to stay properly hydrated?

In February, 2004, after reviewing more than 400 studies, the National Academy of Sciences’ Institute of Medicine rejected this conventional wisdom. It concluded that most men need about 15 of cups of fluid a day, and women about 11 cups. But that includes fluids from all beverages, and the water in food. The vast majority of North Americans already get that much liquid in their everyday diets.

Certain people are actually at increased risk of getting too much water, which can cause sodium concentration in the body’s cells to drop dangerously low and trigger headaches, confusion, and in rare cases even seizures, coma, and death. High-risk groups include people with congestive heart failure or hypothyroidism; those who regularly take certain medications, notably non-steroidal anti-inflammatory drugs such as ibuprofen, ketoprofen, and naproxen; and amateur athletes who take too literally the common advice to “drink as much as possible” during exercise.

Water loss increases after exercise, when temperatures exceed 27C, or at elevations over 1,500 meters, but most people naturally feel thirsty after such stresses and drink more fluids without being prompted. However, people over the age of 65 or so may need to pay special attention to their fluid intake, since the sense of thirst tends to diminish with age. Scanty, strongsmelling, dark-yellow urine indicates that you need to drink more. Finally, while any beverage counts toward your
daily intake, plain tap water does offer several advantages: It’s cheap, thirst-quenching, and calorie-free.

People at increased risk of over-hydration should be especially careful to not exceed the recommended amounts
for their gender. And exercisers should take care to consume at least one cup of fluid an hour but no more than three.