PAMF Health Blog

Be Well, Be Well Informed

Do We Really Need Eight Glasses of Water a Day?

Posted on Nov 18, 2011

In this blog post, Dr. Arnold Aigen, a urologist at the Palo Alto Medical Foundation’s Mountain View Center, addresses the common rule-of-thumb that we all need to drink eight glasses of water every day. He’s a surgical subspecialist who treats a variety of urological medical problems from infections to cancer and kidney stones.

“A day rarely goes by without me seeing a patient who is experiencing the discomfort of needing to urinate too often,” Dr. Aigen says. “While many medical issues, such as prostate or bladder problems, can cause this disorder, I also always ask my patients about their fluid intake.”

We know that water is an essential element for our bodies, one that makes up around 60 percent of our body weight. We can’t live without it, but how much do we need to drink to maintain a healthy level? The common assumption is that we should all drink eight glasses of water every day. That equals 64 ounces or one half gallon.

Arnold Aigen, M.D., PAMF Urology

“Many people rely on the ‘eight glass’ rule, but few know the origin of this recommendation,” Dr. Aigen says. “The most likely source is the National Research Council’s Food and Nutrition Board. Years ago they published the recommendation of one milliliter of water for each calorie of food consumed. For most people, that ends up being about 64 to 80 ounces of water per day. What is often omitted is that they went on to say that much of this is already in the foods you are eating.”

Water constitutes 90 percent of most fruits and vegetables, and about 50 percent of meats and cheese. Additionally, nearly every fluid aside from water that you drink (coffee, teas, juices, sodas) is nearly all water, as well.

“Remember that alcohol and caffeine contain water, but both act as diuretics. These drinks dehydrate you, causing you to urinate out more fluid than you actually drank,” he says.

Importance of Hydration

For our bodies, water is the ultimate precious fluid, an essential element for the brain, body temperature maintenance, digestion, kidney function, circulation, transportation of nutrients and muscle strength.

“Your body has a very effective signal to let you know your water tank is low: thirst. Pay attention to this message!” Dr. Aigen advises. “A good rule to follow is that your intake of all your fluids combined should be enough that you rarely feel thirsty and your urine isn’t concentrated or dark in color. Drink more if you like, but your body’s needs have probably been met.”

Learn more about PAMF’s Urology Services.