Mythbusting

[trixtah]

I've come across that old chestnut that averagely-active people "MUST drink 8 glasses of water a day" four times in the last week, in various formats. And I wish that people would stop spreading that idiocy around. Yes, we do need to consume about that much fluid in a day, but, surprise, surprise, we get at least half of it in our food. The component of that myth that I find particularly galling is that "when you're thirsty, you're already dehydrated". What crap. Thirst is how your body stops you from being dehydrated.

A well-publicised review was carried out a few years ago by Dr Heinz Valtin, who pretty much debunked all those myths after examining extant literature and studies. Here's the part about the "thirsty is too late" myth:

...a rise in plasma osmolality of less than 2% can elicit thirst, whereas most experts would define dehydration as beginning when a person has lost 3% or more of body weight, which translates into a rise in plasma osmolality of at least 5%.

Oh, and as for the rubbish that caffeinated drinks don't count for fluid intake because they act as diuretics? Well, they're not diuretic enough to totally purge you of all that liquid you just consumed, thus upping your total fluid intake. Alcohol, however, will dehydrate you. And if anyone has experienced a hangover, you know how different that feels compared to being a bit thirsty.

Snopes has a good rebuttal of that stupid "75% of Americans are chronically dehydrated" email that appears to be doing the rounds again. But the Valtin study is very readable as well, and good for more background.

Really, like anything else, it all comes down to listening to what your body is telling you. If you are thirsty, drink. Simple.

Comments

[buddleia.livejournal.com]

Oh, I remember a TV study debunking that. They eventually agreed that the original myth had been published without any proper justification in a well known mag and then just circulated.

[trixtah.livejournal.com]

Ahah. I wonder if some stupid magazine or TV show has promoted the myth again, because two people have repeated it to me, I've gotten that stupid email, and I found it on an L/J comm that should know better...?

It's not even a full moon! :-)

[damned-colonial.livejournal.com]

On the other hand, sometimes you *do* just need vast quantities of water. I've been downing close to 4L a day lately and it's working well for me. But then, I've been messing with my exercise and eating habits pretty crazily this last month, and I suspect my body is growing muscle and chewing up fat, which probably takes some extra fluid to manage.

My personal rule of thumb is "if your urine is bright yellow at any time other than early morning, you should drink more water." Or, if actually at risk of dehydration (eg. active in hot weather) the old rule of thumb, "drink til you need to pee." At Pennsic the year I went, I went through 1 gallon of water and 1 litre of Gatorade every day, and I was actually a bit unwell for a couple of days before I figured out those magic numbers.

[trixtah.livejournal.com]

Oh, absolutely. I'm ranting about that kneejerk advice that's handed out to people who are never in non-temperate environments and who exercise by walking to the coke machine twice a day. I myself normally go through about 700ml of liquid in an hour's workout, which is the same as what I drink all day when I'm not exercising. And I sweat quite lightly.

I think sometimes people get used to ignoring their body's cues, and don't notice that they're getting thirsty. Hell, our bodies are all different and have different needs, which the "health" fascists often seem to forget. Frequently. (I should have appended my other rant that pure water is actually not terribly efficient for rehydration, but I'd best leave that for another time.) But I am totally of the view that people should learn what their own bodies need, rather than carrying out spurious advice by rote.

[damned-colonial.livejournal.com]

Yeah. That whole "listening to your body" thing is a weird one. Mine's incredibly communicative if I give it half a chance, but I get the impression this is not commonly the case. I hear lots of people can't even tell where they are in their menstrual cycle without counting. Wtf?

listening to your body

[saluqi.livejournal.com]

Giving your body a chance to communicate is such a loaded thing to do for many people, it doesn't surprise me that people lose the ability.

Sometimes it's trained out of you as well, especially if you're raised in a religious tradition that is big on the mind ruling the flesh. Hell, just being female is enough to get a dose of professionally authorised mind/body disconnect. Plenty of women get told by doctors that common menstrual ailments are all in their head. My sister went through a number of doctors basically telling her she was fat and lazy until her PCOS was diagnosed for example. Part of her believed it too, fortunately other part of her kept looking for a solution and eventually found it - tho' it took years.

I don't have any grand solutions to this, but if I had been told "listen to your body" as a 23 year old I would have nodded wisely and internally dismissed it. Partly because of my values, but also partly because I just didn't understand what it meant. It was martial arts training and bottoming that finally cracked open a few clues. Now of course, my problem is getting it to shut up ;-)

[ataniell93.livejournal.com]

Thank you for posting this because people are always telling me that I need to drink just as much plain water as I do tea, and I hate it. I only want to drink plain water when I've been working out or out in the sun. I have to drink constantly because I have issues with my urinary tract, but I drink tea all day long because I like it better than anything and if I have to drink all day I want to drink something I enjoy drinking.

[trixtah.livejournal.com]

I hate the taste of pure water myself (ironic!), and guzzle tea like it's going out of fashion; I have SO had it with well-meaning lectures about how bad it is. If you don't regularly drink caffeine-based drinks, you'll excrete about a third of what you just consumed. If you do regularly drink them, guess what, they don't appear to have a significant diuretic effect at all.

I suppose you're too polite to tell the water-junkies to take a jump. I quite often wish that I weren't. :-)

[ataniell93.livejournal.com]

It's true, in RL I often am too polite to say that, except to strangers, who have no business advising me.

I have interstitial cystitis or something very like it. If I drink a lot of plain water, it goes through my system too quickly and causes me significant pain if I cannot get to a bathroom immediately. Tea and other such drinks give me a little more time.

[filkferengi]

Thanks for posting this. Listening to our bodies *is* important. Last year at GaFilk I cut back on the drinking, so I wouldn't have to cut out during the concerts. I wound up with a fever of 101 Saturday night & had to blow off Sunday [to be rested up for busing visiting Brits all over the metro area for 4 very full days]. This year I drank more, avoided sitting under the air conditioner, & went home earlier Saturday night. I hated missing out on fun at the con, but was more rested, didn't get sick, & was able to hang around some of Sunday. [Busing the Brits only 2 1/2 days helped, as did getting home earlier at night & getting more rest. Entertaining company's one thing, but there's no need to kill myself doing it, especially now I've shown them where the attraction flyers & transit maps are. :)]

[trixtah.livejournal.com]

Oogh, that sounds nasty. I utterly refuse to sit directly under air-con - it's amazing how much moisture those things suck out of your body.

I'm with you on the wanting to escort visitors around - I want them to feel taken care of, and to give them the best view of my town as possible. However, we all have limits, mental and emotional as well as physical!