You don’t need to drink eight glasses of water a day to prevent dehydration and stay healthy. Every time we say that, readers tell us we’re crazy. Don’t schools and countless experts advise it? What about those people chugging from water bottles all day long? It’s still a myth, and no one really knows where it came from originally. Today this claim is often made by (no surprise) the bottled water industry.
The notion that we don’t drink enough water—that is, at least eight glasses a day—“is not only nonsense, but is thoroughly debunked nonsense,” according to an editorial in the British journal BMJ.
Here are some other water myths. Drinking lots of water does not improve kidney function or help kidneys eliminate toxins—let alone improve overall health. It won’t bathe your organs in extra fluid and thus improve their function. Don’t expect it to lower blood pressure, boost concentration in kids, improve skin tone or prevent headaches, despite the claims.
Yes, water is a great drink. If it comes from the tap, it’s cheap and environmentally friendly. And yes, it may help you control your weight if it replaces caloric beverages. But that doesn’t mean water promotes weight loss.
How much to drink? If you’re healthy and not exercising or working hard in the heat, thirst is your best guide. Most fruits and vegetables are about 90 percent water. Other beverages also provide fluid, as do soups and stews. Coffee and tea supply water, too; it’s a fallacy that they cause a net water loss.
Older people do need to try to drink more water—older bodies cope less well with heat, and thirst may be a less reliable indicator. People with recurring kidney stones may also benefit from drinking more fluids. Basic rule: If your urine is light yellow, you’re drinking enough.