8 cups per day?
by Scott Bird
April 30, 2006
8 comments
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Most people are aware that the drinking of plenty of water is advisable, and anecdotal evidence suggests that more = better (up to a point). However, where did the current guideline of ‘8 cups per day’ come from?
According to Valtin (i) the origin is probably the 1945 recommendation made by the Food and Nutrition Board of the US National Research Council. This stated :
A suitable allowance of water for adults is 2.5 liters daily in most instances. An ordinary standard for diverse persons is 1 milliliter for each calorie of food. Most of this quantity is contained in prepared foods.
The 2.5 litres was changed to 8 × 8 fluid ounce cups in later recommendations, but is otherwise unchanged.
A couple of things are worth noting about this information (which hasn’t really changed in over 60 years). The first is the line ‘An ordinary standard for diverse persons is 1 milliliter for each calorie of food’. This seems much more reasonable to me - tying water consumption to caloric intake - than simply drinking 2.5 litres of water. It would seem sensible that an athlete consuming 4,000 kCals per day would require a greater water consumption than one getting through 1,500 (for health reasons - we’re not talking about preparing for bodybuilding competions here).
The second is the part of the guideline which seems to have been overlooked in later versions - ‘Most of this quantity is contained in prepared foods’. I wonder just how much diets have changed in 60 years.
Further observations - there appears to be a strong emphasis these days on ‘pure’ water consumption. Whilst I always make sure to drink a glass or two of water when also consuming alcohol, coffee or high-protein foods; the bulk of my non-food water consumption comes from green tea. This doesn’t appear - at least in my case - to make any difference whatsoever.
i Valtin H. “Drink at least eight glasses of water a day.” Really? Is there scientific evidence for “8×8”? Am J Physiol Regul Integr Comp Physiol 2002;283:R993-R1004
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Excellent write up. I drink in the range of 3-4 litres of water a day(24-32 cups) however based on the 1ml/calorie I should definately shoot for 4 litres or more per day. Well here comes more trips to the bathroom.
Posted by: Stinn | April 30, 2006 4:56 PM
Stinn, is that 3-4 litres of straight water, or are you including other water-based drinks in that?
Incidentally, 4,000 cals per day is quite a lot to get through (I used to eat about that much, courtesy a fast metabolism).
Posted by: Scott | April 30, 2006 5:05 PM
I drink water as often as possible, usually over 8 glasses. I’ll drink more on hot days, and like a fish if working outdoors. I take my weight when entering the gym, then again after working out or sauna time, and drink the difference in water. And I include even coffee and tea or soda.
Posted by: Alberto Caraballo | May 1, 2006 9:53 PM
That’s 3-4 litres of straight water, I don’t generally drink anything else except for a cup or two of coffee. 4000+ calories isn’t that much when you are 300+lbs.
Posted by: Stinn | May 5, 2006 2:16 PM
Couldn’t help but note the bodybuilding reference. To be perfectly honest, I did worry about Nancy a bit competition day as she dehydrated to look good. Absolutely nutty.
Posted by: Bud Gibson | May 7, 2006 12:07 AM
Bud, it was also on my mind. Makes you appreciate just how much work is involved in prepping for a comp.
Stinn, I’m now starting to feel like a bit of a pig - getting through 4,000 kCals at 185. Actually, I was only about 165 when I started doing that. Oink.
Alberto, the weighing yourself before/after and making up the difference sounds good (perhaps more work than the average person would go through). Makes sense.
Posted by: Scott | May 7, 2006 8:32 AM
Great post. I use the 8 by 8 rule alot. However, a better rule is to drink enough fluid so that your urine is clear or close to clear.
Posted by: Dr. Kal | February 20, 2008 11:18 AM
Cheers Kalvin. I used to do that, but as there are a couple of vitamins that change the colour of it, I try to tie it to caloric intake.
The main culprit - for me personally - is B2; which seems to make its way into every multivitamin I ever use :)
Posted by: Scott | February 20, 2008 5:43 PM