Wednesday, July 9, 2008

64 ounces of water a day?

Does anyone know of any research that demonstrates a need for everyone to drink 8, 8-ounce glasses of water a day? I've got serious doubts and suspect it may be more harmful than beneficial. Perhaps I have missed something. But using a paleolithic model, it seems unlikely that our Stone Age ancestors would have had access to that much water daily given that watering holes are where predators hang out. I would suspect they got little more than a few ounces daily and that was a challenge. Most of their water would have come from their food and small sources such as the dew on leaves, I believe. If this assumption is incorrect, then how is it they thrived for 2 million years eventually populating the planet, but we now have to have 64 ounces a day to be healthy?

How about the oft-repeated stipulation that none of this water can come from caffeinated beverages as they cause a net loss of body fluid? Again, I have never seen any research that supports this notion. Has anyone? In fact, I have found one study that contradicts this belief during exercise (Falk et al, 1990, Effects of caffeine ingestion on body fluid balance and thermoregulation during exercise, Can J Physiol Pharmacol 68(7):889-892).

There are lots of other things that we have been told repeatedly for so many years that everyone now assumes them to be well-supported "facts." I'll get around to them at another time. But for now I'm wondering about all of these people I run into carrying half gallon jugs of water which they sip on all day long until empty and finally go to bed with a mission accomplished.

Can anyone set me straight by pointing out research that supports this notion?


At July 9, 2008 9:08 PM , Blogger Joe said...

I'm thinking low-carb beer is a whole other story.

At July 9, 2008 9:28 PM , Blogger Mike Hardy said...

The 64 ounces of water myth was just recently shown to be bunk, as you say. It hit the newswires this year around April. Here's one example:

Caffeine is similar - it is a diuretic but you have to have higher concentrations of it than normal for it to really kick in, even then I think it was neutral at worst.

Nutrition research in general is pretty bad isn't it? So many myths unquestioned, while at the same time so many proven truths questioned and re-questioned, we're clearly a conflicted irrational species when it comes to our calories.

At July 9, 2008 11:35 PM , Blogger Matthew Pearson said...

You're right Joe, that recommendation has been debunked. In fact, in an article I read recently, no one really knew where that recommendation came from, but it's seared into our collective consciousness. I can't recall the article I read, but I think a recent study put the final nail in the coffin. I did find this, but I'm sure there's lots more out there:

At July 10, 2008 1:37 AM , Anonymous Karl McCracken said...

No idea where this came from. What I can say is that people selling bottled water seem especially keen on it though. Probably just a coincidence ;-)

Like many statistics, my guess is that it's something that's been taken out of context - losing nearly 2 litres of water a day through urine and sweat doesn't sound unreasonable for Mr / Ms Average. But of course, as you point out, most of that can be replenished through what we eat and drink along the way (that coffee in the morning, milk on the cereal, residual moisture in bread & salad at lunch, etc, etc), before we join the queue at the water cooler.

So I think that outside of long workouts, the basic rule that you should drink when you're thirsty seems to make a whole lot more sense - common sense, in fact.

Of course, in longer workouts / races, then drink before you're thirsty is more likely to be the way to go. For me personally in a temperate climate, that's 3/4 of a litre per hour of swimming or cycling, and 1/2 a litre per hour of running. These numbers pretty much double in hot weather (above, say 28C). But everyone's different, and you should measure your own sweat rate so you know what you'll need to replenish.

At July 10, 2008 2:22 AM , Anonymous Micke said...

I can't quote research on either subject, unfortunately. But I can add anecdotal evidence suggesting you are right, especially regarding the dehydration effects of caffeinated beverages.

There is (supposedly, but let's accept that for now) reserach showing that extremely high doses of caffein is dehydrating. However, it is very doubtful if it is possible to actually brew coffee that strong, and in actual practice, normal coffee is far from that strong, and as such is not dehydrating.

I think this myth is pereptuating because some people drink loads of coffee or tea and have to go the the bathroom a lot. They just forget that drinking the same amounts of water would have the exact same effect.

As for the value of drinking much water, I have seen frequent warnings here in Sweden that it may lead to severe incontinence problems in old age. Not something to look forward to, if you ask me...

At July 10, 2008 2:47 AM , Blogger Chris said...

There is no research:

it is an urban myth:

At July 10, 2008 5:55 AM , Anonymous Anonymous said...

I believe I have the answer:

"It got its start when the Food and Nutrition Board of the National Research Council put out a report sometime in the '40s that said adults should drink about a milliliter of water for each calorie of food, which meant that we should drink about 64 to 80 ounces a day.

But the next sentence in the report was ignored. It says, "Most of this quantity is contained in prepared foods." When you think about pasta or rice, you know that it absorbs an enormous amount of water. And we get water in coffee and in beer and in soda, and all the other things that we drink. But it was easy to ignore that part of it, if you were selling water."

By the way, I'm a big fan of the blog.

- Neal Martin

At July 10, 2008 7:54 AM , Anonymous Götz Heine said...

@mike: nutritional research usually lacks taking into consideration what sort of nutrition their gunea pigs are used to, that's why they hardly ever get decent results
@mccracken:take into consideration that sweat rate doesn't take into consideration intercellular water, neither does it take into consideration water stored in the bowels
@Joe: I like that one! Remember when we rode through the desert for four hours? Me just nothing but a water bottle full of tyres, tools? Please take into consideration that none of our ancestors ever figured to move their bodies at 75 to 92bpm of their maximum heart rate daily ;-) Also I found out that the diet you follow plays a major role when it comes to coping with body heat. May sound weird but the more carbs you eat, the more you sweat. We trained pro and amateur athletes likewise and they reported that after they switched their metabolism their water consumption cut down by more than half, also they had no need for mineral or salt tablets any more! For everyone interested in this most interesting topic, here is what I found out in my studies during a decade: An improved fat metabolism is the key factor to water consumption and kidney function likewise.

At July 10, 2008 10:25 AM , Blogger Sketti Scramble said... has a lot of discussion on dehydration and many references to studies on this subject. Very interesting stuff.

At July 10, 2008 10:31 AM , Blogger Michelle said...

Well, I guess I don't need it. But it makes my skin look better. But I don't want to be incontinent either. I'm losing weight and it seems to help with appetite suppression so I'll stick with it for now. But I don't always get the 64 QD so I guess I'll worry about it less when I don't.

At July 10, 2008 11:14 AM , Anonymous Anonymous said...

But using a paleolithic model, it seems unlikely that our Stone Age ancestors would have had access to that much water daily given that watering holes are where predators hang out. I would suspect they got little more than a few ounces daily and that was a challenge. Most of their water would have come from their food and small sources such as the dew on leaves, I believe. If this assumption is incorrect, then how is it they thrived for 2 million years eventually populating the planet, but we now have to have 64 ounces a day to be healthy?
Yes, the eight glasses of water day thing was made up. But so is most this paleolithic model crap. Saying stuff like they got water from mostly due leaves is about the dumbest thing I have every heard. Modern plumbing has not been around that long and there are still people who do not have it and have to compete with predators. We don't have to speculate about how people used to get water and we certainly can't use uninformed speculation as a basis of why not to drink water. I have a great deal of respect for you Joel, and read your posts often, but this post just knocked my opinion of your down a few notches.

At July 10, 2008 3:27 PM , Blogger Ryan Denner said...

64oz - Probably to compliment the high salt diet that most people eat (but doubtful of your blog readers).

At July 12, 2008 7:14 AM , Blogger John said...


There's also a lot of good research on caffeine by Larry Armstrong, PhD who did a great talk on the subject at either the 2002 or 2003 ACSM annual conference.

Here's the title: Armstrong LE (2002) Caffeine, body fluid-electrolyte balance, and exercise
performance. Int J Sports Nutr Exerc Metab 12,189-206

He showed that caffeine ingested during exercise did not have much of a diuretic effect, if any, but that athletes loss less fluid thru urination than they ingested. Premise was that the body is a lot smarter than we give it credit and during exercise the kidneys will decrease the amount of fluid loss through urine production since more fluid will be loss through sweat and respiratory losses.

There's enough studies that demonstrate a performance benefit from caffeine that the dehydration claim doesn't make sense, since if there was a significant dehydration effect from caffeine, we should see some decrease in performance.

I also have a handout some place from an old lecture that I did that I'll dig out and send your way about caffeine and exercise.

John Martinez, MD
Coastal Sports & Wellness Medical Center
San Diego, CA

At July 12, 2008 9:48 AM , Blogger Greg Remaly said...

how much and what people drink is far too dependent on the individual, his/her environment, and what the individual does in a given day.

Merely by asking this question, you are giving far too much credence to this sadly outdated notion.

At July 14, 2008 5:07 AM , Anonymous Anonymous said...

Since switching to the Paleo Diet, I have noticed that my body doesn't need as much water than when I was eating a non-paleo diet. It also seems like my body doesn't store water like it did on a non-paleo diet.

At July 21, 2008 3:22 AM , Anonymous Anonymous said...

Hi I believe the 64 ounces of water myth came from the 2nd world war. When people were rationed they were allowed 2 litre of water per person per day.

At August 12, 2008 9:37 AM , Blogger Chris Trousdell said...

don't know how good this reference is, but basically says that the average person secreats about 1.2l per day, so you should replace this as the minimum, but the bottom line is to drink when your thirsty!

At August 20, 2008 6:48 PM , Anonymous Chris said...

As someone who has personally struggled with both dehydration in very hot climates and hyponatremia due to misguided efforts to "get enough water" in training/racing conditions, I have found one reliable metric to judge my need for fluids.

If the color of my urine is light yellow to clear, I'm hydrated. If it's dark yellow to brown, start drinking. With this metric I can always judge upon waking up in the morning how far ahead/behind I am in fluids. I have also found I can gauge my sodium status pretty reliably by looking at my hands and checking for swelling. Puffy hands = hyponatremia is starting. Need more salt.

I have also found that urine color can be indicative of muscle breakdown in high-effort events, which may indicate problems with pacing or nutrition. Bright colors - neon yellow, neon orange - are a sure sign of muscle breakdown for me. Usually has a different odor too.

Sorry if this grosses you out, but after 10 years of IM racing and experiences with medical treatment for acute dehydration and hyponatremia (not at the same time!) this method has proved reliable for me.

At May 7, 2009 6:13 PM , Anonymous Anonymous said...

Bottle water companies started this myth


Post a Comment

<< Home