Do I Need to Drink More Water?

I’m currently training for my first half marathon in September, and the water issue has been on my mind lately.  Am I drinking enough?  When do I need to drink it?  What about when I’m not exercising?

I think we’ve all heard that we’re supposed to drink 8-8 oz glasses of water per day, or roughly 2 litres.  From what I’ve read, however, this number is pretty arbitrary, varies with gender and activity levels, and doesn’t take into account the water you get from food and other beverages.

And forget the idea that caffeine dehydrates you.  Studies now conclude that it doesn’t act as a diuretic, unless you’re talking large doses in people who haven’t consumed any caffeine for awhile.  Links to the studies are here and here (thanks to Health Habits, who had a post on this topic).  So if you’re a coffee, tea, or (like me) diet cola drinker, you don’t have to pound back an extra glass of water to “hydrate” yourself after consuming some caffeine: the caffeinated drink actually counts toward your liquid consumption for the day.  I also found Diet Detective Q & A’s on hydration to be a useful read on this topic.

This still doesn’t answer the question I had, though, which was, “How much water do I need to drink, if not 8 glasses per day?”  Well, apparently there’s no easy answer.

This Mayo Clinic article on how much water you should drink says you can follow the 8 glasses per day guideline, but you basically want to drink enough so that “you rarely feel thirsty and produce 1.5 liters (6.3 cups) or more of colorless or slightly yellow urine a day.”  This is in agreement with what I read in Sports Nutrition for Endurance Athletes by Monique Ryan, who writes that “you can monitor your hydration status by checking the color and quantity of your urine.  Clear or lemonade-colored urine reflects adequate fluid intake, while darker or apple juice-colored urine…indicates that you need to step up your fluid intake.”  She also says that you should “urinate at least four full bladders every day.”  Who knew?  Also, vitamin supplements can change the color of your urine, so you may have to consider volume over colour.  Alrighty, then.

I’m totally NOT going to be measuring, by the way.

Water and Exercise Definitely Mix

So, how much should I be drinking before a workout?  Going back to Sports Nutrition for Endurance Athletes, the author suggests taking in 720 mL or 24 oz/3 cups of fluid approximately 2 hours before a workout, plus another 240-480 mL (8 to 16 oz, or 1-2 cups) half an hour before.

Unfortunately, we aren’t camels: we can’t store water.  According to the Diet Detective Q & A’s article, any extra liquid will be out of your body in half an hour.  However, that doesn’t necessarily mean more is better.  This Runner’s World article discusses hyponatremia, which is a life-threatening condition caused by drinking too much water.  I don’t think I’m in any danger of this happening to me, because I drink when I’m thirsty while running and I’m consuming Gu and/or Gatorade during my long runs, but certainly the article is worth a read (even if it is a little old).

Okay, so what about during a workout?  In Sports Nutrition for Endurance Athletes, Ryan strongly recommends weighing yourself before and after a workout (unclothed, of course) to gauge how much water you’ve sweated away.  Take your weight loss (pounds or kilograms – doesn’t matter), calculate how much water corresponds to that weight (1kg = 1 L or 1,000 mL; 1lb = 15 oz), and add in how much water your consumed during your run.  That’s the total volume of water you lost.  Then divide that by how long you worked out (say, 2.5 hrs) to figure out how much you sweat per hour.  That would give you a rough guideline, but you still have to remember that how much you sweat will vary with weather conditions and how well you’re acclimated to the weather.  Sheesh!  Gets kind of complicated.

For more simple guidelines, check out this article by Runner’s World.  It suggests 3-6 oz every 15 to 20 minutes.  That translates to anywhere from 9 oz (just over a cup) to 24 oz (3 cups) per hour.  Guess it’s more of a starting point, rather than a “hard and fast” rule.

What About Post-Workout?

The Runner’s World article suggests consuming enough so that you have to pee within 60 to 90 minutes – 1 to 3 cups is usually adequate.  Sports Nutrition for Endurance Athletes recommends drinking 20 to 24 oz (2 1/2 to 3 cups) of fluid for every pound you lose during your workout (so you have to weigh yourself before and after).  Runner’s World suggests anything from 8 to 24 oz.  Again, I’m sure this will vary with the type and intensity of the workout and weather conditions.

What I Am Taking from All of This

  • eight glasses of water a day is pretty much a myth, so no need to obsess
  • caffeine in normal amounts does not dehydrate you; in fact, caffeinated beverages add to your fluid levels
  • drink enough that your urine is clear or light-coloured; if it resembles apple juice, you should be drinking more
  • drink lots before a workout so that you are well-hydrated, 3 cups 2 hours before and 1-2 cups half an hour before
  • during a workout, aim to consume 1 to 3 cups per hour and expect my fluid needs to vary with weather, intensity, and type of exercise
  • you should drink 1 to 3 cups of fluid after your workout, or enough that you have to use the washroom within an hour and a half
  • if you’re feeling hard-core about it, weigh yourself before and after your exercise session and calculate away!

Well, high-five to you if you made it to the end of this post.  That was kind of long-winded, but I figured I’d write it all down in one place so that I don’t have to look it all up again.  Hope someone else finds it helpful, too 🙂

Bottoms up!


4 thoughts on “Do I Need to Drink More Water?

  1. 45before35 says:

    I adore your well-written, researched posts. I can totally tell you are a graduate student, soon to be Dr with access to databases:).

    Question – where do you get your pics?


  2. mostlyfitmom says:

    I get most of them from Click on images, and then you can search the clipart. I’m no photographer, so it’s a good thing they have a variety of pics! 🙂

    Yeah, I’ve written a few papers in my time, although now most of my schoolwork focuses on the practical – dentistry is very hands on!


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