8 Glasses of Water a Day: Fact or Fiction?

Julie Shenkman
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For decades, mothers have been telling their children to drink at least eight glasses of water per day to prevent dehydration and stay healthy. Drinking water is important, but researchers now believe eight glasses per day may be too many for some people. Instead of following an arbitrary guideline, you should listen to your body and hydrate as necessary.

The need for eight glasses of water per day is a myth that has been debunked by several scientists. Unfortunately, it is one of the most common myths floating around the health community. Celebrities often say drinking water helped them lose tremendous amounts of weight or eliminate acne and other skin problems. Diet books promote drinking water as a way to curb hunger and prevent overeating. There are even doctors who tell their patients to drink at least eight glasses of water per day.

The problem with this myth is that there is absolutely no scientific evidence to back it up. In fact, too much water can cause serious electrolyte imbalances, resulting in seizures and other medical problems. Dr. Aaron Carroll says there is plenty of water in fruits and vegetables, so there is no need to supplement a balanced diet with an additional eight glasses of water per day. Most beverages also have plenty of water in them, so people who drink natural fruit juices or decaffeinated teas likely need fewer than eight glasses of water per day to meet their hydration needs.

Dr. Carroll says drinking water when you are thirsty is the best way to get enough water in your diet. Contrary to popular belief, feeling thirsty is not a sign that you are already dehydrated. Thirst is simply a natural signal that reminds you to drink water and other fluids. It's especially important to listen to your body when playing sports or spending a lot of time in the sun. Drinking water is a great way to help you avoid dehydration while working or playing in the summer heat.

Although not everyone needs eight glasses of water per day, some people do need more water than others. Diarrhea and vomiting cause water loss, so be sure to drink extra water if you have an illness that causes either of these symptoms. If you work a physical job that has you sweating all day, replenish lost fluids with water or sports drinks. Contact your doctor immediately if you are too ill to keep water down. You may need intravenous fluids to help you feel better and prevent electrolyte imbalances.

Water is essential for life, but too much water can actually cause serious problems. If you are concerned about dehydration, listen to your body carefully. Eating plenty of fruits and vegetables, limiting your caffeine consumption and drinking water when you are thirsty are good ways to prevent dehydration. If you are still worried about your water consumption, ask your doctor for guidance.

Photo courtesy of suphakit73 at FreeDigitalPhotos.net



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    All the exceeds are dangerous to health.

  • Nancy Anderson
    Nancy Anderson

    Thanks @Keith and @Gary. Appreciate your comments. Certainly one should listen to their body to determine how much water they might need in a day. It is true that we get water in our food and other liquids. However, you have to remember that you won't receive as much benefit from the water in say a cup of coffee as you would in a bowl of soup due to the caffeine in your coffee. Each person is different and only they can determine how much water they need. 8 glasses a day is the recommended amount based upon research but everyone is different.

  • Gary P.
    Gary P.

    I haven't in my 71 yrs drank 8 glasses of water a day, but I have drank a glass or two of water beyond what I would drink if I were thirsty. Using thirst as the criteria for drinking water in our sedentary society does not seem to be to be adequate. We need decent urine output even if we aren't thirsty.

  • Keith Enste
    Keith Enste

    If ;you're thirsty you need to drink fluids like water; but, if you're also drinking other beverages during the day you are already supplementing your basic fluid needs. Simply put; if you are thirsty: you need to take in some fluids like water. Remember also that many of the other beverages that we drink during our day are primarily composed of water. So, if you're thirsty drink; if not do not worry. Remember; also too much of anything is not good for you. I remember reading a report about a woman who was so concerned about contracting cancer; that she used to drink water constantly; unfortunately, she did not die from cancer: instead, she essentially drowned in her own tissues that were overwhelmed by the inordinate amounts of water she consumed. She never contracted cancer however; but she died just the same. You know your body better than anyone else; if you're thirsty; have some water; if not, it is alright to skip a glass or more.

  • latishia m.
    latishia m.


  • Erica J.
    Erica J.

    Although I don't necessarily believe that 8 glasses of water is essential for health, I do believe that getting the proper amount of water is crucial for maintaining a healthy body and lifestyle, I think it will vary with weight, age, activities and lifestyle. To much water can also be dangerous as the article states. I know that marathon runners sometimes have the risk of consuming to much water in a short period of time which can be life threatening! Nice article and good read.

  • Esther M.
    Esther M.

    I agree to this information it's absolutely true. Thanks

  • Adrienne Cook
    Adrienne Cook

    I've been on a high protein, low carb & low sugar diet for 6 mo & have lost 35 lbs. Drinking lots of water is vital to body functions, weight loss & hydration. Experts with this diet recommend that each person determine their personal water intake in ounces, based on their starting weight. For example I weighed 230 lbs when I began my food program. Take that number & divide it in half, in this case 115, is how many ounces of water my body needed. That's nearly 14 eight ounce glasses of water! True that we get water in fruits and vegetables but I count non-caffeinated tea & coffee as well. The color of your urine is a good indication if you're staying hydrated. A clear light yellow is a good measure to stand by.

  • selma+ o.
    selma+ o.

    Thanks to the tip

  • Paula Z.
    Paula Z.

    Who is Dr Carroll and what are his credentials and why should we believe him after successfully following the 8glasses of water a day mantra? Of course, It is different for each person depending on other liquids they drink, but I do believe 8 glasses (one gallon) is a good baseline of liquids to consume daily. Certainly, it is difficult to chart your liquids as they may come from other sources. There is no mention of the hydration effect of alcohol? I am in fitness and active and only drink water and need even more than 8glasses a day. My question is, before we debunk any good practice rules we have been following shouldn't we at least have a few educated opinions, tests and surveys?

  • No  P.
    No P.

    May is not good for some people. But is a lot better than juice and sodas. 8 glasses of water is not really to much water. And starting the morning with one and ending the day with another one is very good way to add a healthy routine to your life. Soon you will be drinking almost 8 glasses of water a day without even knowing it. I had kidney problems growing up. I learned many years ago to LOVE WATER.

  • Jessica M.
    Jessica M.

    The amount of water you need per day is actually based off your body weight. And being thirsty is the first sign that your body needs water!

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