Wednesday, June 23, 2010

The dehydration myth

Last month a fruit juice company put out a press release stating that there was new research that 52% of Australians were dehydrated. Evidence provided – zero. We just had to take their word for it.

The 8 glasses myth

Later in the press release came the statement that 64% of us aren’t getting the “recommended eight glasses of water a day”. Who made that recommendation? We are not told. Don’t bother looking either because I have never seen a health authority in the world make that statement. Do you drink 8 glasses of water a day? I don’t. It’s winter here. During summer I might, especially if I’m out on my bike. In winter, sitting at my puter I’d much prefer a hot cuppa thanks.

No single level of water intake

Do you really need to drink 8 glasses of water a day? No. There is no harm in doing so and if water is the only drink you have then it is probably a smart decision. The official Nutrient Reference Values (NRV) we have in Australia state “there is no single level of water intake that would ensure adequate hydration and optimal health for the apparently healthy people in the population”.

The NRVs suggest an average intake of 3.4 litres a day, based on the assumption that 800 mL will come from foods like pasta, apples and potatoes and the remaining 2.6 litres will come from non-alcoholic fluids like milk, tea and coffee. (Note that 2.6 litres is about 8 glasses; it doesn't have to all be drunk as water).

What about caffeine?

The first question that comes to mind is “Don’t caffeinated drinks dehydrate you?” The simple answer is no, they don’t. If you do drink tea, coffee, or cola you will need to pee out some of the metabolites of caffeine but this obligatory urine is a lot less than the fluid in the drink. For example, for a 250 mL cup of tea, your obligatory urine needs are around 50 mL, leaving the other 200 mL as part of your fluid intake. Only alcoholic drinks have a dehydrating effect. For more detailed science on hydration and caffeine download my free ebook called Nutrition Fibs [].

What does it all mean?

Drinks like soft drink, fruit juice, tea, coffee and milk, and foods like fruit, vegetables, meat, yogurt, soups, stews and steamed rice all have appreciable amounts of water that contribute to your fluid intake. Water is an excellent fluid too; it’s just not the only fluid as some imply. Under normal day-to-day circumstances if you pee every 2-4 hours and your pee is lightly coloured then you are likely getting enough water each day. And that marvel called nature also offers a helping hand when your body gets low on water – it makes you thirsty. How neat is that?

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