You’re dehydrated. You feel tired, and you have a headache that just won’t quit. When you drink some more water, all of those things go away, right? Well, not exactly. Drinking gallons of water isn’t going to fix symptoms of dehydration automatically.
You’ve probably heard advice like this your whole life:
“Drink at least eight glasses of water per day,” the Mayo Clinic says.
“How much water should you drink? The eight 8-oz glasses of water rule is right on,” WebMD says.
“By the time you feel thirsty, you’re already dehydrated and need to take action to catch up,” Health.com says.
They’re all saying the same thing: Staying hydrated is important. However, the 8-glass rule might be a little misleading.
People didn’t obsess about how much water they were drinking for most of human history. It was only in the last few decades that this “eight glasses” thing started getting spread around.
Where does it come from?
- An article published by the National Institutes of Health (NIH) in 1942 stated that “most authorities agree that an ordinary standard of intake is about 1 milliliter (1 cubic centimeter) for each calorie of food.” For a person eating the recommended 2,000 calories per day, that would be around 64 ounces or 4.7 liters of water per day.
- The National Research Council (NRC) in 1946 stated that “a suitable allowance of water for adults is 2.5 liters (about 15 glasses) daily in most instances.” This would be about 1,900 ml or about 11 glasses per day.
- An article published by the National Research Council (NRC) in 1956 stated that people living in hot areas might need to drink more than four glasses of water per day, but people in cooler climates will need less. Other than that, they recommended a daily intake of about 1 milliliter for each calorie eaten.
- A book published by the U.S. Army in 1970 stated that a person needs to drink enough water, so his urine is “almost colorless.”
- An article published by the Mayo Clinic in 1981 stated that a person needs to drink enough water, so his urine is “light yellow.”
- The National Academy of Sciences (NAS) publishes Dietary Reference Intakes every few years. In 2005, their Food and Nutrition Board published recommendations for total water intake in chapter 9. That chapter establishes a “tolerable lower intake level” of 1.6 liters per day for men and 1.1 liters per day for women.
That covers a pretty big range of recommendations. From 4 glasses to 11 glasses within a day, how have we concluded that 8 glasses is the magical number?
The best thing you can do for your body is to consult your doctor for a recommended water intake. They’ll look at your diet, exercise, and overall lifestyle to help you find an amount that’s suitable for your body’s needs. There’s a lot of studies and professional advice out there. However, without having a health expert confirm your physiological needs, there’s no sure way to know exactly how much you should be drinking in a day.
For something more remarkable involving water, check out our article Did You Know That There Are Lakes INSIDE The Ocean?