How Much Water Should You Drink?

Everyone knows the answer to how much water should you drink is eight glasses, right?

In this article, I will answer how much water should you drink and debunk the top 10 hydration myths based on the latest medical science.

The Top 10 Hydration Myths

1. Drink 8 Glasses of Water

The biggest hydration myth is that you must drink eight glasses of water every day.  Even my children have been taught this in school.

Guess what, no medical study has ever shown that you need eight glasses of water.  The best medical studies I could find recommended five and six glasses daily.

The first was a study of 20,297 Seventh Day Adventists which showed that drinking five or more glasses of water each day was associated with a 50% decreased risk of a heart attack.

The second study, recommending six glasses of water, included 47,909 people.  In this study, those drinking six or more cups of water were observed to have a 51% lower risk of bladder cancer compared to people who only drank one cup daily.

Both of these studies should be interpreted with caution as they were just observational studies.  These studies don't prove that water was the reason why people had less heart attacks or bladder cancer.  An alternative explanation for these findings is that water drinkers tend to be more health conscientious, eat a healthier diet, and are more likely to exercise regularly.

So where did the 8 glasses a day myth originate?  My best guess is that it came from a 1945 publication by the National Research Foundation.  This 1945 report wasn't based on any medical studies.  Since 1945, the recommendation has become urban legend and the rest is history.

2. Caffeinated Drinks Dehydrate You

The second biggest hydration myth is that caffeinated drinks dehydrate you.  When put to the test in a medical study, this was simply not true.

In fact, there was no significant difference in how well a caffeinated drink, like a carbonated beverage or coffee, hydrated you compared to water.  While I would never recommend that you drink anything other than water, the take home message of this study is that any drink hydrates you.

3. You Can't Drink Enough Water

With all of the sensationalized media reports every summer of people dying from dehydration, many people now carry huge water jugs and drink water all day long.  Can you get too much of a good thing?  Yes.

There is actually a medical condition called water intoxication.  If you drink too much water it can cause hyponatremia.  Hyponatremia occurs when sodium levels are too low in the blood.  When this happens it can cause confusion, brain swelling, and even death.

Interestingly, one study found that 13% of Boston Marathon runners had hyponatremia.  This is because they over hydrated with water and sports drinks.  Over compensating with fluids, following massive sweat losses, caused dilution of their blood and resulting hyponatremia.

The key point of this study is that drinking fluids in moderation is best for endurance athletes.  You don't want to over hydrate with endurance events.

4. You Need Sports Drinks When Exercising

Does the risk of hyponatremia with exercise mean that you need to start drinking Gatorade when working out?  Absolutely not.  In fact, studies show that sports drinks don't protect you from hyponatremia.

Sports drinks are nothing more than sugar water with a few electrolytes.

Fortunately, even if you sweat a lot, you can get all the electrolytes you need from eating real food.  For example, you can get all the magnesium you need from nuts, seeds, and greens.  Table salt or tomato juice will get you your sodium.  Fruits and vegetables pack in the potassium.

5. You Can't Rely on Your Thirst

Many Internet reports will tell you that you can't rely on your thirst.  According to these reports, once you are thirsty it is too late.  You are already dehydrated.

However, that is not the opinion of the world's leading scient...