How much water do we actually need?
You may have heard some variation of the advice that you need to be drinking eight glasses of water per day -- but, what does this actually mean? Is there any evidence to support such a seemingly arbitrary measurement?
The recommendation for eight glasses (around 2 liters) of water per day likely originated in the 1940’s when the Food and Nutrition Board suggested 2.5 liters of water per day, including fluids from any prepared foods. Since then, this advice has been highly contested.
Some claim that the suggestion was based on no actual medical evidence, and others still believe you only need to drink water as often as you are thirsty.
There is some evidence that the pre-existing suggestions are more than enough water and that drinking more than the two liters (or eight cups) or water will likely not have any major health benefits, aside from potentially preventing recurring kidney stones.
Now, the CDC does not actually recommend a certain intake of plain water per day, but instead suggests a blanket hydration goal that is inclusive of other beverages and fluids from food. The latest US Dietary Guidelines also refrain from recommending a specific fluid intake -- though, they do emphasize the importance of choosing plain water over flavored water or sweetened beverages.
It’s important to note that most notable sources agree that fluid intake from food, as well as unsweetened beverages and even coffee and tea (though not with excessive caffeine) all contribute to your daily water goals.
The current consensus is that water intake, while vital to overall health and well-being, does vary across individuals. Factors such as age, race, and activity levels appear to play a significant role in how much water you need to function optimally. Recommendations for your specific conditions may be found here, or by speaking with your current doctor or dietician if available.
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