Wednesday, 14 January 2015

Are you getting Cold Dehydration?

Another good reason for drinking water is that it stops you getting dehydrated.

Obvious?  The average adult is made up of about 40 litres of water – that’s 60% of your body mass.  Lose as little as half a litre, and symptoms start appearing; by the time you’ve lost a litre, you’ll be suffering from impaired cognitive function, reduced physical performance, headaches and symptoms of fatigue.

In the long-term, there is evidence to suggest that chronic mild dehydration is associated with increased risk of a number of conditions, including constipation, urinary tract infections, hypertension (high blood pressure), coronary heart disease (CHD) and strokes.

But you won’t get dehydrated in Winter because it’s cold … WRONG!

It’s actually easier to become dehydrated in winter.  In summer, it’s hot (well, sometimes) and you sweat, both of which trigger thirst – which makes to want to drink.

In winter, neither of those things happen; however, when you go out in the cold, your body withdraws blood from your extremities in order to preserve heat, which is why your fingers and toes get cold so easily (they have a large surface to volume ratio and are therefore very good a radiating heat).  Suddenly, you have the same amount of blood occupying much less space so the kidney’s kick in and deposit the excess in your bladder (otherwise your blood pressure would rocket)… this is why going out in the cold an trigger the desire to wee.

So far, so good.  Now what happens when you come in from the cold?

The blood returns to your extremities – except suddenly there isn’t enough to go round… and you can’t get it back from your bladder, even assuming it’s still there!

…And bingo, you’re dehydrated but not necessarily feeling thirsty – and even if you are feeling thirsty, it’s cold outside so the tendency is to go for a nice warming cup of tea or coffee (both of which are diuretics) or even have a nip of something slightly harder (which will dilate your blood vessels even more).

Which is why step one of the #5stepping will help you stay healthy in winter and summer, just replace one caffeinated and one alcoholic drink per day with a half-pint glass of water – there’s your 1% and what you don’t need, your kidneys will dispose of!

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