How Much Water Do We Really Need?

By Bethany Rundell

It’s a fact: Water makes up 55 to 75 percent of our body composition, depending on our age. It’s also a fact that when our bodies lose more water than they take in, dehydration may occur.

But is it a fact that we need to drink at least eight glasses of water a day — the typical recommendation? Not necessarily.

Lester Carrodeguas, M.D., a family medicine physician with Baptist Health Primary Care in Kendall, said that while clinical dehydration is rare, maintaining optimal levels of fluid helps our bodies work properly. “The eight-glass-a-day rule is easy to remember and safe for most people to follow,” Dr. Carrodeguas said. “That’s why it’s often repeated, even by healthcare providers.” But, he added that a person’s actual daily fluid needs may differ widely.

The Institute of Medicine has concluded that establishing a daily recommendation for fluid intake is not possible because so many factors influence a person’s needs. These factors include age, size, metabolism, health conditions, physical activity and environmental surroundings.

A good portion of the fluids we consume — about 20 percent— comes from our food. People who eat a diet rich in fresh fruits and vegetables get fluid when these foods break down in their digestive system. Another factor to keep in mind is how active you are and how much you sweat.

Dr. Carrodeguas pointed out that athletes, people who live in warmer climates like South Florida and those with certain health conditions may require more daily fluids. Conversely, elderly people and individuals with congestive heart failure or certain kidney diseases may need to limit their fluid intake.

Most people will experience symptoms before they become dehydrated, Dr. Carrodeguas said. Signs of dehydration include extreme thirst, muscle cramps, rapid heartbeat or palpitations, light-headedness, confusion and lack of perspiration.

A simple way for most people to judge their level of hydration is by looking at the color of their urine, according to the National Institutes of Health. In response to dehydration, the kidneys conserve water and excrete more concentrated urine; the more concentrated the urine, the darker the color. A clear, light-colored urine is a fair indicator that your fluid level is good. 

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