If you think that drinking eight glasses (two liters) of water per day is hard or downright impossible, you aren’t alone.
Widespread questioning and doubt surrounding this claim spurred me to take a closer look at the research behind the “eight glasses a day” adage.
The so-called “8×8” rule originated in 1974 with nutritionist Dr. Fredrick J. Stare, who urged his patients to drink eight ounces of water between six and eight times every day. Turns out, there is virtually no scientific evidence that we need to drink this much water.
According to Harvard Medical School, the average healthy adult should consume “four to six cups” of liquid each day. This includes water we get from food, coffee, juice, milk and even beer.
On top of that, each person requires a different amount of water based on activity level, sweating, the weather, physiology, health, state (pregnant or breast-feeding), and diet.
There’s also no evidence to support the claim that “feeling thirsty” means you are already dehydrated.
“As humans, we have this homeostatic system, so when we need water, we feel thirsty,” explains Stuart Galloway. Galloway is an associate professor in physiology, exercise, and nutrition at the University of Stirling. Drinking when you feel thirsty will maintain your body’s hydration to within 2% of its ideal state.
This is fine for most people, even athletes, adds Galloway.
Those most at risk of dehydration include children and the elderly, whose sense of thirst is not as accurate. Perhaps the advice about feeling thirsty was aimed at parents and caretakers, and has been misconstrued over the years to apply to healthy adults?
Ideally, says Galloway, you should be urinating between five and seven times per day.
Another issue here is that no pharmaceutical company is going to invest in researching water. That is because it’s a free resource that they can’t put a label on and sell. This general lack of scientific knowledge opens the door for other companies to make exaggerated claims about the benefits of drinking water.
The claim that we should “detox” our bodies with water is “a load of rubbish,” says Galloway. That’s what your kidneys are for.
The claim that water will give you glowing skin is also misleading. Chronic dehydration will have a negative impact on your skin. But drinking more water than you need will do nothing more than send you to the bathroom.
In conclusion, the best ways to stay hydrated are to drink when thirsty (prioritize water over sweet beverages and alcohol) and to monitor the color of your urine: if it is dark, you need more fluids; if it is pale yellow, you are hydrated; if it is clear, you may be drinking too much water.