World Water Day: How Much Water Should You Really Be Drinking?
To celebrate World Water Day (Tuesday 22nd March 2022), we thought we’d dive deeper into the question of water for good health. How many glasses should you actually be drinking each day?
Water has been described as a neglected, unappreciated, and under-researched subject. Interestingly, many scientific papers studying the need for proper hydration are actually funded by the bottled water industry. Either way, it turns out the often quoted “drink at least 8 glasses of water a day” is too generic and has little underpinning scientific evidence.
Water your body
The human body is made up of 50-75% water, which forms the basis of blood, digestive juices, urine and perspiration, and is contained in lean muscle, fat and bones. While the body can last weeks without food, it only manages days without water. This should tell you just how important adequate water intake is for your body!
Where did the “8 glasses a day” come from?
This recommendation can be traced back to a paper from the 1920’s by Edward F. Adolph, in which the author measured his own urine and sweat, and determined humans lose about 3% of body weight in water per day - this comes out to be about 8 cups. Consequently, for the longest time, water requirement guidelines for humans were based on measurements from this one person!
Water and your health
Scientific evidence suggests that not drinking enough water is linked with constipation, overeating, and the development of kidney stones. Amazingly, more recent research also suggests pure water may actually protect against some modern killer diseases!
A Harvard University study tracking 48,000 men found that the risk of bladder cancer decreased by 7% for every extra daily cup of fluid consumed. So, a high intake of water, such as 8 cups a day, may reduce the risk of bladder cancer by about 50 %, potentially saving thousands of lives.
One of the more convincing arguments to drink more pure water (as opposed to any old fluid) comes from research on 20,000 men and women in the Adventist Health Study—about half of whom were vegetarian but all of which generally followed a healthier lifestyle compared to the average American. Those drinking 5 or more glasses of water per day were found to have about half the risk of dying from heart disease compared to those who drank 2 or fewer glasses daily. Importantly, just like in the Harvard study, this protective effect of water was found after adjusting for various other lifestyle factors that can influence results, such as diet and exercise.
World Health Organization recommendations
Based on the best evidence to date, authorities such as the World Health Organization recommend between 2 to 2.7 litres of water a day. That’s 8 to 11 cups a day for women, and 10 to 15 cups a day for men. However, their recommendations are for water from all sources, not just beverages. We get about 1 litre of water from food and what our body makes itself. So, this might be translated into a recommendation for women to drink 4 to 7 cups of pure water a day, and men to enjoy 6 to 11 cups (assuming only moderate physical activity at moderate temperatures).
Are you drinking enough water?
Here are a few of our tips to up your dose:
- Drink 1-2 glasses of water as soon as you wake up and before breakfast
- Drink before, during, and after exercise
- Keep water at your workstation
- Travel with a water bottle handy
- Drink a glass or two in the early evening
- Jazz up your water – add some lime, lemon or cucumber slices - or try unsweetened sparkling water
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