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The Water Myth

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Pete McK:
I see that the Mountaineering Council of Scotland are warning about dehydration in this weather and peddling the same old drink at least 2 litres of water myth. The best advice I know came from my buddy who is a GP and outdoor enthusiast: Drink when you are thirsty, because your body knows best.

Lyle Brotherton:
It's the myth that just won't go away Pete and one close to my heart. When I was young we were taught that we needed 8x8 =  8 glasses of 8 ounces of water a day, yet later in life I discovered that this notion is based on flimsy and misinterpreted science.

Heather Morning, Mountain Safety Adviser with the Mountaineering Council of Scotland, who gave this advice has done so in good faith, she is excellent at her job and is no doubt in the same boat as the vast majority of folk about the issue of water intake.

The military have a keen interest in keeping their battlefield assets, a euphemism for squaddies, ready for action. Plus water is heavy to carry, 1 litre = 1 kilogram and it is a logistical problem to supply to the battlefield. As a consequence they have conducted loads of trials concerning hydration; from the simple let them drink what they want to intravenously introducing fluids into volunteers, another euphemism for you are going to do as your told, so the volunteers cannot tell how much fluid they have had in the tests.

It is thought that the 8x8 rule came from a recommendation by the US National Research Council, back in 1945, that adults should consume 1 millilitre of water per calorie of food they ingest, thus:

Men: 2500calories/day = 2.5 litres of water/day
Women: 2000calories/day = 2.0 litres of water/day

The floor in this reasoning is that all foodstuffs contain water and many at very high percentages:

Lettuce   95%
Broccoli 91%
Milk 89%
Orange juice 88%
Carrot 87%Yogurt 85%
Apple 84%
Chicken 68%

And we get between 25-40% of our fluids this way.

The second floor is that we get fluids from almost anything that we drink, from tea and coffee, the diuretic effect of these beverages is negligible, milk, fruit juice, and even light alcoholic drinks such as beer. So the guidelines to drink pure water is not only misleading, they are wrong.

The important thing is that if you are a healthy individual already drinking enough tea, milk etc., there is no evidence that drinking lots of water water as well will achieve anything other than making you pee frequently. In fact, over-hydration in itself can cause problems with electrolyte levels and blood sugar levels.

Adult male soldiers, who work in a temperate climate, consume on average 3,000 calories/day and drink on average 1.2 litres of fluids per day, of which pure water usually represents less than 25%, if at all. On very hot days with strenuous activity they may get up to 2 litres of fluid over the entire day, including breakfast and their evening meal.

Your GP mate is spot on about drinking when thirsty because we get thirsty long before there is any significant loss of bodily fluids. It takes less than a 2 per cent rise in the concentration of the blood to make us want to drink, while the body isn't officially regarded as dehydrated until a rise of 5 per cent or more.

As a footnote, I have been working on a project about water-purification in the outdoors and I will publish the results of this work on the Forum :)

Lost Soul:
Interesting and relevant thread for this time of year.  I sweat a lot so need lots of water, I try and drink on the when thirsty principle.  And I know only too well the problem of carrying the stuff around with me.  Particularly in summer.  I have a 3 litre Platypus.  In summer for a day out that gets filled up (6.5 lbs weight) and often as not on a hot day gets all used up .

In winter I half fill it and often return with 1/2 a litre or more.

As for a quick and simple test for checking correct hydration levels.  Signs seen in a Gentleman's Lavatory in a factory in Hertfordshire - you are wondering what is coming next aren't you.

Monitor the colour of your urine.  If you are properly hydrated it will be a pale straw colour.  The darker it gets the more dehydrated you are.  If it's clear then you are over hydrated then as Lyle says it can cause problems with electrolyte levels and blood sugar levels.

There have been some classic high profile cases of this happening.  Sian Williams the BBC presenter collapsed doing or at the end of the London Marathon a few years back from over-hydration.  She just drank every bottle of water that was handed to her with catastrophic results.  She ran again this year but with a carefully planned hydration strategy.  Not everybody survives the collapse as she did. 

Callum:
The amount of youngsters who arri9ve at our centre with packs of bottled water yet at the same time poor footware is lamentable.

British tap water is probably the best in the world in terms of purity and where we live in the Lake District it tastes great too.

On our posting to Kenya we had an Old School CO. He insisted on the troops taking salt tablets and consuming a pint of tea every day. The tablets somehow found their way into the red dust and the one pint became two of tea, no dehydration, maybe this is why it is such a popular beverage in got countries?

The myth I would like to bust with water, and I totally agree with everything written so far in this thread, is that of bottled water being better for you because it is purer and contains minerals. I recently learned that one of the big bottled water brands is actually tap water to which they add minerals.

Of course we need minerals to maintain good health, BUT, the minerals that our bodies need and use do not come from water; they come from the foods we eat, including fruits, vegetables, and animal products. Less than 5% of minerals our bodies use come from bottled water if you were consuming the mythological 8x8 (2 litres) of the stuff per day. In fact, to get the necessary minerals from bottled water you would need to drink in excess of 840x8 of bottled water to get the RDA of most minerals

The bottled water industry is a multi-billion pound concern and it is their marketing strategies and paying for professionals to spout forgive the pun - this nonsense which perpetuates this myth.

Lyle Brotherton:
A little off piste, but if you are travelling and need a supply of cheap bottled water Lidls sell a six pack for 99 pence - good to store in the boot of your car.

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