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Mythbusting
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:
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.
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.