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General Discussion / Re: The Water Myth
« on: July 23, 2014, 11:21:19 AM »
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
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
