How Much Water Do You Really Need?

by in Healthy Tips, July 9, 2009

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You should be drinking 8 to 10 glasses of water a day, right? Well, as it turns out, there’s no scientific research to back up this number. Learn how to figure out how much water you should be getting and other ways to stay hydrated this summer.

Hydration Basics
Your body relies on water for a lot more than quenching thirst. Water makes up about 60% of your body weight, and it helps control our body temperature, flush toxins and retain moisture. Because we lose fluid through breathing, sweating and bathroom breaks, we need to constantly replenish to keep body fluids in balance.

The truth is, fluid replacement doesn’t have to come just come from straight-up water — all fluids and many foods contribute to hydration. That’s right — everything you drink and foods like soups, fruits and vegetables count. Foods actually account for about 20% of our average fluid intake, while beverages make up the other 80%.

Now that’s not carte blanche to replace all the water you’ve been drinking with sugar-y soda or coffee, but it does mean that everything counts. Recommendations for how much “water” to drink should actually be recommendations for how much total fluid you need in a day. Of course, water is still the best choice because it’s calorie-free and gets absorbed quickly. Americans get more than 20% of their daily calories from beverages, and it’s easy to overdo it, which can mean extra poundage.

But Caffeinated Drinks Dehydrate You, Right?
That’s also a myth, too. Research supports that caffeine-containing drinks do not have a negative affect on your overall hydration levels.

How Much Do You Need?
The Institute of Medicine recommends about 11 cups of fluids a day for women and 15 cups for men on average. If you exercise regularly or spend time outside in the heat, you need more. Women that are pregnant or breastfeeding also need more.

The absolute best way to tell if you are properly hydrated is to check the color of your urine (I know, it’s kinda gross, but it works). Dark yellow means you’re dehydrated, and light yellow or clear means you’re getting enough fluids. Also pay attention to your sweat rate. If you sweat more because of exercise or a hot day in the sun, you need more to drink in order to replenish.

Tap or Bottled?
Nutritionally, there’s virtually no difference between tap and bottled water — unless you live in an area where the water has been deemed undrinkable, of course. In fact, tap water may contain more minerals than the bottled stuff. Bottled water is often a convenient option, but it requires a lot more energy to produce all those plastic containers — plus, it can get pricey. According to Planet Green, one liter of bottled water requires 2,000 times more energy to produce than one liter of tap water! Reusable drinking bottles are the eco-friendly way to go.

If plastic bottles are the only option, re-fill them with tap water a few times to get some extra use out of them. Check out our tips for using safe plastic containers and drinking bottles.

    Sure-Fire Tips for Staying Hydrated
  • Carry something to drink with you at all times (preferably calorie-free)
  • Eat lots of fresh fruits and veggies — they have a high water content and loads of nutrients
  • Check your urine color to make sure you’re getting enough fluids
  • Monitor your sweat rate — the more you sweat, the more you should drink
  • All fluids count!

Bottom Line: All fluids and foods contribute to your hydration, but good ol’ water is still the best choice. Drink fluids with meals and throughout the day (and some extra if you exercise) to make sure you’re getting enough.

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Comments (15)

  1. Just yesterday CamelBak unveiled results of a first-ever water bottle study conducted at Pepperdine University. The study tested whether water bottle design affects consumption levels. Well, it does … quite significantly. I’d love to get the complete release in your hands!

  2. Krikri says:

    Right. The more you sweat, the more your consumption should be so the 11 and 15 cups serve a a general guide.. Tap water has been known to offer more minerals as bottled water has regulatory restrictions as to how much minerals and additives they can include. There has even been this argument on fluoridated water – that bottled water companies need to ensure sufficient quantities for consumers. Some tap water sources have it abundantly and others in limited quantities.

  3. TNN says:

    I am a third year medical student and the fact about caffeine is not true. Caffeine actually does play a role in dehydration. It activates what is called the angiotensin renin system in the kidneys that causes you to excrete water at a higher level. Also, the sodium and sugars in soft drinks and other caffeinated drinks have a similar effect.

    • Evelyn says:

      I agree with TNN…by my own personal experience and those of my clients. There is a lot of research out there and some of it is contradictory.

  4. danawhite says:

    Thanks for your comment TNN – you bring up a very important point. Caffeine certainly does trigger some water excretion by the kidneys, but the fluid present in caffeinated beverages still contributes to your daily fluid intake.

  5. Dennis says:

    What, if any, negative impact is excessive water/fluid intake? At what point does it occur?

  6. danawhite says:

    Hi Dennis – great question! Too much water can lead to a condition known as hyponatremia where sodium levels in the blood drop dangerously low. Symptoms may include headache, muscles weakness and cramping, confusion, fatigue and nausea. How much is too much is different for everyone (but I typically only see this condition with endurance athletes). Follow the guidelines mentioned in the article to stay properly (and safely) hydrated.

  7. danawhite says:

    Hi Dennis – great question! Too much water can lead to a condition known as hyponatremia where sodium levels in the blood drop dangerously low. Symptoms may include headache, muscle weakness and cramping, confusion, fatigue and nausea. How much is too much is different for everyone (but I typically only see this condition with endurance athletes). Follow the guidelines mentioned in the article to stay properly (and safely) hydrated.

  8. danawhite says:

    Hi Dennis – great question! Too much water can lead to a condition known as hyponatremia where sodium levels in the blood drop dangerously low. Symptoms may include headache, muscle weakness and cramping, confusion, fatigue and nausea. How much water is too much is different for everyone (but I typically only see this condition with endurance athletes). Follow the guidelines mentioned in the article to stay properly (and safely) hydrated.

  9. Lori says:

    ABOUT THE GIRL WHO DIED DRINKING WATER….. there's a huge difference between drinking gallons of water at one time and drinking it thru out the day.
    Some people say you can safely drink up to half your body weight in ounces… more if you are doing major workouts.

  10. jan says:

    I'm a fight attendant and I notice such a difference when I drink alot of water on a flight ,that helps stay hydrated and from being fatigue the next day.

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