The New guidelines for Daily Water Intake

The 8 x 8 Rule: Drink eight, 8-ounce glasses of water per day for good health. This rule has been repeated and tossed around for decades, but did you know it's actually outdated and over-simplified advice? The 8 x 8 Rule is pretty limiting since water needs can vary widely between individuals, but luckily, there are some new guidelines for daily water intake that are more user-friendly.

Where Did the 8 x 8 Rule Come From?

The recommendation to drink eight glasses of water per day can be traced back to 1945. The Food and Nutrition Board originally suggested that people drink one milliliter of water for each calorie of food they consumed. As the average person consumed about 1,900 calories per day, this translated to a recommended 1,900 mL of fluid per day — or about 64 ounces. There were a few shortcomings to this recommendation, which the National Academy of Medicine (which has absorbed the Food and Nutrition Board) now acknowledges.

First, people tended to misinterpret the advice. The board really meant to advise that people consume about 64 ounces of fluid per day including fluid from foods, but people assumed they needed to drink this fluid in addition to any fluid found in their food. Second, the recommendation ignored the fact that people's water needs vary greatly based on environment, activity level, age, weight, and a host of other factors.

The New Guideline: Drink to Thirst

Rather than making such a specific recommendation, the National Academy of Medicine now recommends that people drink according to their thirst. They specify that most men need about 15 cups of fluid per day, and most women need about 11 cups. This may sound like a lot, but bear in mind that much of the liquid will come from the foods you consume. If you eat plenty of hydrating foods and just drink when you are thirsty, you should get enough water.

Should You Track Your Water Intake?

The new recommendation to "drink to thirst" is broader than the recommendation to drink eight, 8-ounce glasses of water per day. However, all recommendations have their shortcomings and caveats — this one included. Some people are not sure whether they are really thirsty. Other people may ignore signs of thirst because they're really busy during the day. If you are concerned you are not drinking enough water just by relying on thirst as an indicator, it can still be helpful to track your water intake.

If you do track your water intake, how many ounces of water a day are needed? Starting with the 8 x 8 Rule is not a bad idea. If you get eight glasses per day, in most cases, you will be off to a good start. However, you will want to set your goals even higher if any of the following apply to you:

  • You are nursing or pregnant.
  • You spend a good portion of your day outside in the heat.
  • You exercise or have a really active job.
  • You are above average weight.
  • You have a health condition that leads to frequent vomiting or diarrhea.

On the other hand, if you eat a lot of hydrating foods, like fresh fruits and veggies, you may not need a full eight glasses of water per day. If you have water available but are just not thirsty, then defer to the new guidelines for daily water intake — drink to your thirst.

How Can You Make Sure You're Drinking Enough?

Whether or not you choose to formally track your daily water intake, there are a few tips you can employ to make sure you're getting enough fluid.

Consider using a water tracker bottle that is marked with the time and ounces consumed. Carrying this bottle with you will ensure you always have water available, and will also allow you to keep an eye on how much you drink throughout the day. Water tracker bottles come in various sizes, including 64 ounces, 50 ounces, and 32 ounces, so you can choose the bottle most in line with your water consumption goals.

Another strategy, which works especially well for really busy people, is to check in with your thirst level every half hour. Set an alarm or a reminder if you have to. Simply take a second to assess whether you feel thirsty, and if you do, take a few sips of your water.

The 8 x 8 Rule is not a terrible place to start when wondering how much water should you drink a day. However, there are newer daily water intake recommendations that are more accommodating to the variety in peoples' individual needs. It all boils down to the following: keep water handy, drink when you are thirsty, and keep an eye on your intake to ensure you're remembering to drink.

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