Do You Really Need to Drink Eight Glasses of Water a Day?

You may have heard the common suggestion that we should consume eight glasses of water a day, but individual needs aren’t necessarily one-size-fits-all. This month, we’re digging deeper to find out how much we really need to drink every day.

Madge Barnes, M.D., a primary care physician on the medical staff at Texas Health Family Care – Grand Prairie, a Texas Health Physicians Group practice, says we may have been following an outdated suggestion for decades.

“One theory as to the origin of the eight by eight rule is that a research organization released a report in 1945 stating that the average person needs to drink 1 milliliter of water per calorie of food consumed,” she says. “The average caloric intake at that time was about 2,000 kilocalories a day, which would be roughly 2,000 milliliters (which is about 64 ounces) or eight 8-ounce glasses of water. There is no scientific evidence to support the eight glasses per day.”

According to the Centers for Disease Control and Prevention, water plays a crucial part in helping our bodies regulate our temperature, lubricating and cushioning joints, protecting the spinal cord and other tissues, and eliminating waste via perspiration, urination and bowel movements. Adequate daily water consumption also prevents dehydration, which can lead to confusion, mood change, constipation, kidney stones and overheating.

It’s particularly important to stay hydrated, as our bodies are composed of up to 60 percent water. The lungs are made up of 83 percent water, followed by 79 percent of the muscles and kidneys, 73 percent of the brain and heart, 64 percent of the skin and even 31 percent of the bones.

Brittney Bearden, a registered dietitian and sports nutrition manager at Texas Health Sports Medicine Fort Worth, says that while necessary daily water intake will vary from person to person, you may actually need more than you think.

“The recommendation from the Institute of Medicine is higher than eight cups per day,” she says. “Their general fluid recommendation for women is 91 ounces and for men 125 ounces. Roughly 20 percent of water intake comes from food, so 80 percent comes to approximately 73 ounces for women and approximately 100 ounces for men. However, it’s important to remember that water needs vary between individuals as age, body weight, muscle mass and activity level influence needs.”

Barnes recommends an easy way to figure out how much water to drink and provides an easy way to judge hydration.

“I recommend drinking half your weight (in pounds) in ounces as a minimum, based on weight, physical activity or hydration status,” she says. “Persons with chronic medical conditions, such as heart disease or heart failure, should check with their PCP/cardiologist to determine their hydration needs.

“The color of a person’s urine can also be a rough indicator of hydration status but is not an absolute. Urine should be colorless or the color of lemonade with an adequate fluid intake. Urine that is as dark as apple juice could indicate inadequate intake as well as other conditions. If a person rarely feels thirsty, water intake is likely sufficient.”

The CDC recommends increased water intake if you live in a hot climate, are breastfeeding, are running a fever or are experiencing diarrhea or vomiting. While we absorb water from both food and drinks, plain water is the best way to consume plenty of H2O, as it is calorie-free.

Bearden says that physically active individuals especially need to pay attention to their fluid intake, as they will lose more water while sweating.

“It’s important to hydrate properly and consistently throughout the day and continue hydrating throughout exercise,” she explains. “Fluid needs are influenced by activity level and individual sweat rate. One way to monitor fluid losses during activity is to weigh in before and after activity and drink 16 to 24 ounces of fluid for every pound lost.

“Electrolyte-containing sports drinks are wise to incorporate for exercise lasting longer than one hour. Carry a filled water bottle throughout the day to promote consistent water intake. Monitor urine color for hydration status, as urine should be light yellow.”

The CDC reports the majority of Americans don’t consume enough water each day, and that daily intake varies by age and other factors. Between 2005 and 2010, American youth drank only an average of 15 ounces of water a day, while adults consumed around 39 ounces. Daily water intake is also lower in older adults, lower-income adults and those with a lower education level.

Among youth in the United States, water intake is lower among younger children, Mexican American children and non-Hispanic African American children. Additionally, youth who drink less water tend to drink less milk and more sugar-sweetened drinks, consume fewer fruits and vegetables, eat more fast food and get less physical activity.

While it’s clear that most of us likely need to increase our daily water consumption, is it possible to drink too much water?

“While it is uncommon, you can drink too much water — which can lead to negative health effects,” Bearden explains. “Overhydration can lead to nausea, vomiting and changes in mental function such as confusion and disorientation. It can also lead to dangerously low sodium levels which cause more severe symptoms. To avoid overhydration, spread your water consumption out throughout the day and avoid drinking large amounts of water in a short period of time.”

Barnes explains the results of drinking too much water a bit further.

“When a person consumes too much water, the sodium content in the body is diluted and the kidneys can’t excrete the surplus of water, leading to a condition called hyponatremia. The condition can be life-threatening, so it is always important to check with your PCP regarding water/fluid needs.”

Now that you know the facts, the CDC provides the following tips for increasing your daily water intake:

  • Carry a water bottle to make it simple to consume water all day long.
  • If you find it easier to drink cold water, freeze water bottles and sip on them all day long as the ice melts.
  • Add wedges of lemon, lime or other fruits or even cucumber, to add flavor to your water and encourage increased consumption.
  • When you’re at home, at work or at a restaurant, choose water over sugar-sweetened beverages, which will also eliminate unnecessary calories and promote weight management, and encourage your children to do so as well.

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