- (a) 3 to 6 glasses
- (b) 8 to 10 glasses
- (c) At least 12 glasses
- (d) It’s complicated
Correct answer:
- (d) It’s complicated
What you should know:
These days you are likely to hear from many sources that people should drink at least 8 or more glasses of water a day, but it turns out that there’s no scientific basis for this idea. If you’re interested to know the source of the misinformation, check out this Snopes article.
That’s not to say that science has never addressed the question of how much water people should drink. In 2005, the National Academies of Science, Engineering and Medicine published a page turner called Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate (2005). In 92 pages, not counting references and appendices, Chapter 4 presents an exhaustive analysis and summary of research related to water in the human body—including all of the ways in which the body loses and produces water (it might surprise you to learn that your body actually makes water).
The conclusions? There are many, but these stand out:
“While it might appear useful to estimate an average requirement…for water, it is not possible.“
“[N]ormal hydration status for all adults… can be achieved with a wide range of water intakes.”
“[T]here is no single daily total water requirement for a given person, and need varies markedly depending primarily on physical activity and climate, but also based on diet.”
“No adverse effects have been reported with chronic high intakes of water in healthy people consuming a normal diet, as long as fluid intake is approximately proportional to losses.”
“Acute water toxicity has been reported due to rapid consumption of large quantities of fluids that greatly exceeded the kidney’s maximal excretion rate of from 0.7 to 1.0 L/hour.” (That’s roughly 3 to 4 glasses per hour.)
Deciding What’s Right for You
Based on the amount of water a person’s body generally loses each day (if it’s not very hot and they’re not being highly active), men would need to consume somewhere in the range of between 3.5 to 5 liters (14 to 20 glasses) of water a day, and women around 3 liters (12 glasses) per day, to replace that lost water.
On average, people in the 20 to 64 age range consume only about a third of their daily water by drinking water—they get the other two-thirds from other beverages and food.
According to the professional publication Nursing: April 2009 – Volume 39 – Issue 4, p 14, you can check for dehydration with this procedure:
“Assess skin turgor [elasticity] by gently pinching a fold of skin between your thumb and forefinger. The skin you select, such as below the clavicle or on the abdomen, sternum, or forearm, should feel resilient, move easily, and quickly return to its original position when released after a few seconds.”
