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Posts tagged ‘Caffeine’

How much water do we really need to drink?

I think we have all heard at one point or another in our life that drinking 2 liters of water per day does wonders to your mind and body. But is this really true? Let´s find out.

2 Liters per day is about drinking 8 glasses of water per day, and if you have ever tried doing that, you have realized that you spent a lot of time in the toilet. So, where did this mythical number come from? Why 2 liters and not for example 1.5 or 3 liters?  Well, it probably started from a study done in the 1940s, where researches calculated that 2 liters is how much water a person’s body consumes in 24 hours, so WALLAH, there you have it, that´s where the magical number comes from. But what also came out of that study, and what a lot of people don´t know, is that we get much of the water we need each day from our food, and this does not include the number of drinks like coffee and tea most of us consume every day. And NO, coffee and tea DON´T DEHYDRATE YOU. Although coffee and tea may act as diuretics, the amount of dehydration caused by these beverages is not equivocal to the volume of the fluid. Caffeine has been shown to cause one milliliter of fluid loss per milligram of caffeine. So let´s give an example to explain.

  • A normal cup of 260 milliliter of coffee has around 90 milligrams of caffeine, so if the caffeine causes one milliter of fluid loss per milligram you would still have 170 milliliter of liquid, So, in other words you gained 170 milliliter of liquid, that´s called hydration.

So we know half of our body is made up of water, we know water is vital to keep the important chemical reactions in our body functioning. But the idea that you should drink 2 liters of water per day has absolutely no evidence to back it up. So what should you ? Drink when you are thirsty, if you have to drink more than 8 glasses per day do it, if you have to drink less than that also do it. In other words, listen to your body and you will be perfectly fine.


Fink H, Burgoon L, Mikesky A. Practical Application in Sports Nutrition. Jones and Bartlett Publishers, Inc 2006.

Grandjean AC, Reimers KJ, Bannick KE, Haven MC. The effect of caffeinated, non-caffeinated, caloric and non-caloric beverages on hydration. J Am Coll Nutr. 2000;19:591–600.

Food and Nutrition Board of the Institute of Medicine. Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate (2004). Accessed October 11, 2006.

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