How Much Water Should You Drink?

Hi, I'm Liz Moser, a Mayo Clinic and National Board Certified Health and Wellness Coach.

My clients often ask me how much water they should drink each day.  Is it 8 cups? Or even a gallon a day?  Yes, water is a large component of our overall body and it’s essential to our health and wellness. So, how much should we be drinking each day?

First, let me address the eight glasses a day dictum. 

It turns out the often quoted “drink at least eight glasses of water a day” maxim has little underpinning in scientific evidence. So then where did that idea come from? The recommendation was traced to a 1921 paper, in which the author measured his pee and sweat and determined we lose about 3% of our body weight in water a day or about 8 cups. Consequently, for the longest time, water requirement guidelines for humanity were based on just one person.

OK, so eight glasses is a concept that’s been floating around since the 1920s, and here we are in 2020. A century later! What's the current research showing and what are the benefits of drinking water? 

Water is your body's principal chemical component and makes up about 50% to 70% of your body weight. Your body depends on water to survive.

Every cell in your body needs water to function correctly. For example, water:

• Gets rid of wastes through urination, perspiration, and bowel movements

• Maintains your body temperature

• Lubricates and cushions joints while protecting  sensitive tissues
  here is evidence that water consumption staves off heart disease and some cancers.

• The brain shrinkage associated with dehydration may play a role in cognitive impairment and levels of energy, alertness, and happiness.

How much fluid does the average, healthy adult living in a temperate climate need?

Based on all the best evidence to date, the U.S. Institute of Medicine, and the World Health Organization recommend that:
Women drink between 2.0 and 2.7 liters (8 to 11 cups or 64 – 88 ounces) of water a day.
And,
Men drink between 2.5 to 3.7 liters (10 to 15 cups or 80 – 120 ounces) a day. 

However, this includes water from all sources, not just beverages.  We get about a liter of water from our food and our body, which makes water as well.

This translates into a final recommendation:

Women need to drink 4 to 7 cups or 32 to 56 ounces of water a day.
Men should consume  6 to 11 cups or 48 to 88 ounces of water each day.

That’s assuming only moderate physical activity at average ambient temperatures.  If you are exercising heavily, please drink liquids before, during, and after exercise.  

We can also get water from all the other drinks we consume, such as milk, juice, and herbal teas, composed mostly of water.  Even caffeinated beverages, wines, and some spirits contribute to your daily water intake.

And, as I mentioned we get about a liter or 39 oz of water from our food.  For example, many fruits and vegetables, such as watermelon, berries, and spinach, have high water content.

You might need to modify your total fluid intake based on several factors:

• Exercise. Are you sweating heavily while working out? Then please replenish your fluids. It’s important to drink before, during, and after your workout.

• Environment. Heat and humidity cause sweating and those fluids need to be replenished. Also, high altitudes require extra hydration.

• Overall health. You lose fluids when you have a fever, vomiting, or diarrhea. Please follow your doctor’s advice when ill. Perhaps even rehydration solutions like Pedialyte etc. are necessary.

In general, how do you know if you’re drinking enough?

Your fluid intake is probably adequate if:

• You rarely feel thirsty.

• Your urine is colorless or light yellow.

Your doctor or dietitian can help you determine the amount of water that's right for you every day.

Should I worry about drinking too much water?

Drinking too much water is rarely a problem for healthy, well-nourished adults. Athletes occasionally may drink too much water to prevent dehydration during prolonged or intense exercise.

In general, the kidneys have a hard time processing more than 3 cups or 24 oz of liquid within an hour.  So, anything more than 3 cups per hour exceeds the limit your kidneys can handle and may dilute the electrolytes in your brain. 

And lastly, does drinking water promote weight loss?

Research shows that drinking two cups or 16 ounces of cold water within the hour prior to a meal promotes weight loss. It increases norepinephrine levels by a magnitude at least as great as that elicited by ingesting 250 mg caffeine.  So, drinking  16 ounces of water within an hour prior to a meal boosts your metabolism up to 30%.  One cup of water works, but two is better, and room temp or hot water also works but again, cold water is most effective.

In sum, to prevent dehydration and make sure your body has the fluids it needs and assuming you live in a moderate climate and are an average exerciser, drink between 4 to 7 cups or 32 to 56 ounces if you are a woman and between 6 to 11 cups or 48 – 88 ounces if you are a man.   

Or, drink when you are thirsty and maintain urine that’s clear to light yellow.

If you exercise heavily, live in a hot, humid climate, or if you are ill, your water needs are higher, and please follow the advice of your doctor or trainer. 

Also, to boost your metabolism and promote weight loss, drink 16 ounces of cold water within an hour prior to your meal.  And lastly, don’t exceed 3 cups of water in one hour as that approaches the limits your kidneys can process and may dilute the electrolytes in your body.  

I’m Liz Moser, a Mayo Clinic and National Board Certified Health and Wellness Coach, and thank you for reading this blog about how much water we shoul dconsume each day.  If you have any questions about this blog, about health and wellness, or wellness coaching with me, please reach out via my website at lizmosercoaching.com

Bye for now and be well,

Liz