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March 20, 2005
8 glasses of water a day???

All day long, I hear my preceptors telling their patients to drink at least 8 glasses of water a day.  I also hear that for every glass of caffeine, they need 2 of water.  So, I began to wonder if all this drinking really is necessary? 

The 8 glasses of water rule began when the Food and Nutrition Board recommened approximately "1 mm of water for each calorie of food" which would average about 64 to 80 ounces a day.  However, the next part of the recommendation was "most of this quantity is conatined in prepared food."  So, it seems that America only listened to the first half of this recommendation.

According to Family Practice News, 8 Glasses of Water a Day is no longer the Mantra.  Most healthy individuals remain adequately hydrated by allowing their thirst to dictate their intake. 

Additionally, I found that caffeinated drinks (coffee, tea, and soda) DO count towards your daily total.  Dilute alcholoic beverages as beer also count toward your intake if taken in moderation.  Their diuretic effect has been found to be only transient in nature.

Thus, drinking whenever you are thirsty is an adequate guide of how much your body needs.  Looking at the color of your urine is also helpful.  If you are not taking vitamin B2 (which turns your urine bright yellow), then your urine should be very light yellow.  A deep yellow is an idication that you are not intaking enough. 8 glasses is not necessary, but can it be harmful?  According to many experts it can.  "Even modest increases in fluid intake can result in 'water intoxication' if one's kidneys are unable to excrete enough water (urine). Such instances..have led to mental confusion and even death in athletes... and in ordinary patients."

Other disadvantages of a high water intake: (a) possible exposure to pollutants, especially if sustained over many years; (b) frequent urination, which can be both inconvenient and embarrassing; (c) expense, for those who satisfy the 8 x 8 requirements with bottled water; and (d) feelings of guilt for not achieving 8 x 8.

So, let thirst be your guide and do away with the 8 glasses of water a day!!!


Great post. I too have been hearing that recommendation for a while and wondering if it really was beneficial. The tip about looking at the color of your urine is also very helpful. I will definitely keep this in mind when talking to patients and with my own diet

I really like the post, as I have often wondered how much water we all should drink. Recommending 8 glasses of water a day still might be a good way to promote healthy fluid intake though(ie substituting water for soda or kool-aid). One major item not mentioned: it is necessary to drink additional water for certain circumstances (strenuous exercise, long airplane flights, hot weather, kidney stones). FYI: The article in the last link regarding "water intoxication" failed to mention that the teenager that died after ingesting the Ecstasy drank close to 3 gallons of water in a short period of time (Boulder, CO 2/01). This was more than enough water to wash out her kidneys.

When reading this post I too thought of that kid who died from drinking too much water. I do get sick of hearing that and unfortunately, I think some people really overdo it. I think peeing every hour isn't really normal or necessary, but when you're consuming 12oz of water in an hour, that's what happens. Great to know that we can let our own bodies tell us what we need and can trust that!

I agree with Lindsey. My cousins drink 8+ glasses of water, and although I think they're in pretty good shape, I'm not sure how much all that water has to do with it. We all need water, and if you're always that thirsty, go ahead and drink, but I'd also recommend getting screened for DM. But I have heard that as we age, our thirst mechanisms don't work as well, and I think for the elderly population, it might not be such a bad idea to recommend drinking even if they're not thirsty in order to maintain their hydration.