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drink water

May 18, 2010 Leave a comment

Whether you pay attention to it or not, water affects every aspect of our lives – from sanitation to cooking to, well, you.  About 70% of our bodyweight is water.  We can’t live without it.  But many people aren’t getting enough.  This is the case not just in developing countries where it is difficult to access safe drinking water, but also in developed countries where clean water is plentiful.  In fact, a study shows that up to 27% of people in the US might suffer from chronic dehydration.

So what?

Well, here’s a list of problems you’re more likely to encounter if you’re not drinking enough water:

  • Cancers (urinary tract, colon and breast)
  • Heart disease (mitral valve prolapse)
  • Kidney stones
  • Childhood obesity
  • Diminished mental and physical performance
  • Diminished salivary gland function

But how much water is ‘enough’?  The very helpful answer is: it depends.  It depends on your weight, food consumption, physical activity, environment and diuretic consumption (caffeine and alcohol).   As a guide, you should be drinking 1ml of water per calorie of food.  So, if you’re eating 2,500 calories per day that means you should be drinking 2.5L of water per day.  However, approximately 1L of that will come from food (especially fruits and vegetables) and another 250ml coming from the water of oxidation.  That leaves 1.25L, or 5 cups, that needs to come from drinking water.  Follow?

However, these are the calculations for an inactive individual.  If you/’re doing exercise then you are sweating more and need to drink more.  A rough guide is to consume 1L of water per hour of exercise.  So, want to figure out how much water you should be drinking per day?  Try this calculation:

[Number of calories/1,000] + [hours of exercise x 1] – 1.25 (fluids from food and oxidation) = number of litres per day

So, if I eat 2,800 calories per day and exercise for 45mins, my water intake calculation will be:

[2,800 calories/1,000] + [0.75 x 1] – 1.25
2.8                 +      0.75     – 1.25  =  2.3L

So, I would need to drink 2.3L, or about 9 cups, of water per day to keep my fluid levels constant and avoid dehydration.  This doesn’t account for diuretics like coffee and alcohol, which actually create a negative fluid effect – which is why a late night drinking session can result in headaches and vomiting, which are symptoms of dehydration.  Make sure you drink even more water if you’re drinking caffeine and alcoholic drinks – you’ll be glad the next morning!

Dehydration occurs with as little as 1%-2% loss of bodyweight from fluids.  Even just 1% loss impairs exercise performance.  That means non-diuretic fluid intake (from water, sports drinks, etc) must be enough to keep bodyweight constant for optimal physical performance.  So when you’re at the gym, running, or whatever, make sure you’re drinking something to replenish your lost fluids.  There is plenty more to say about ideal exercise drinks (e.g. protein and carbohydrate combinations), but I will leave that for a future blog.

Always err on the side of too much water if you’re in doubt as to how much you need to drink.  You can use the urine test as a crude method for judging how hydrated you are: dark is dehydrated and pale is adequately hydrated.  Just remember that more exercise, food and diuretics (coffee, alcohol) mean more water is needed.  So drink up.