Does shaving make your hair grow back thicker? Can swallowed gum stay in your body for seven years? Will cracking your knuckles give you arthritis?
Most of us know these are superstitions by now. But what about the claim we should drink eight glasses of water per day? As it turns out, this is just more fiction.
Oklahoma Medical Research Foundation immunologist Eliza Chakravarty, M.D., said that particular statement was taken out of context in a decades-old scientific paper and has continued to be perpetuated despite the lack of any definitive evidence.
So without scientific proof, why are we bombarded with reports of the dangers of dehydration?
“It’s like playing telephone as a child,” Chakravarty said. “It keeps getting passed on without going back to the original literature, and the little changes over time turn it into dogma because everybody has said it for so long. It takes someone going back to the root source and saying, ‘Wait a second’ to make it stop.”
This old wives’ tale is back in the spotlight thanks to pediatrician Aaron E. Carroll, M.D., who recently wrote “No, You Do Not Have to Drink 8 Glasses of Water a Day” for The New York Times. Carroll has worked for much of the past decade to dispel this misconception by going back to the original studies.
Carroll believes the myth likely stems from a 1945 Food and Nutrition Board recommendation stating people should drink 2.5 liters of water per day, but it was lost over time that most of that water is contained in prepared foods and beverages. Eight additional glasses of pure water a day is simply unnecessary, said OMRF’s Chakravarty.
Your body is constantly losing water through breathing, urination, sweat and so on, but the eight glasses per day is more than you would lose under regular circumstances.
The fluids you drink throughout the day will meet the majority of your needs and can be supplemented by eating fruits, vegetables, broth soups and more. “So many things contain water,” said Chakravarty. “There’s no magic number that you need to drink this much or that much.”
This is no license to go off drinking nothing but soda, coffee and beer, but the fear of dehydration has been overblown. If you eat and drink regularly, said Chakravarty, there is little reason you should be in danger save for an existing medical condition or extreme physical exertion or temperatures.
Your body will give you plenty of warning if water reserves are running low, Chakravarty said.
“Listen to your body when you’re feeling thirsty or dizzy or something like that,” she said. “Those are ways your body signals you to tell you need water.”
Since it isn’t necessary to walk around with a water bottle or CamelBak all the time, is there any danger in drinking too much water?
Not really, unless you have special medical conditions pertaining to salt balance in the body, said Chakravarty, but it’s exceedingly rare.
“Kidneys are amazing organs,” she said. “No matter how much water you drink or salt you take in, they regulate the levels in your body so they stay within a pretty narrow range.”
The 8-glasses-a-day mantra might be a fable, but that doesn’t diminish the importance of water to human health.
“Water is critical, making up 60 percent of your body weight and is required by every system in your body,” said Chakravarty. “Without water, cells can’t survive. Water is the main component in every single cell and is the driving force of your bloodstream, which carries nutrients and takes away waste.”
Water clearly is necessary, but what’s the doctor’s recommendation? The exact amount varies from person to person but, said Chakravarty, it’s wise to grab for water when you’re thirsty for many reasons, including overall health, weight management and cost.
“Water is always a good decision, but any fluid will keep you hydrated under normal circumstances,” she said. “Listen to your body when you’re thirsty and pay attention at times where you might be at risk, like when you’re doing strenuous exercise, are out in the heat or running a fever. Those are all times you’ll want to be vigilant, but there is no magic number.”