The Hydration Myth

good healthMany healthcare professionals recommend drinking 6-8 glasses of water per day for good health and optimal performance.  As a result of these recommendations, it has become accepted by society that in order to have good health and body performance, we must drink lots of water.  It’s known as the 8 X 8 rule – drink eight 8 ounce glasses of water per day for good health – but is it really necessary?   A medical doctor, Margaret McCartney, of Glasgow Scotland recently challenged these claims in a commentary in the British Medical Journal (BMJ).

Dr. McCartney attended the annual scientific meeting of the Hydration for Health initiative.  She suggested that the concept of drinking 6-8 glasses of water per day for good health is a theory that is being pushed by the bottle water companies in an effort to make money.  She states that she has found no research that supports the claims that the drinking 6-8 glasses of water have any health benefit at all. In fact, she states that drinking excessive amounts of water can lead to hyponatremia.  As well, she notes that drinking excessive tap and bottled water exposes individuals to dangerous chemical compounds and pollutants.


Hyponatremia is a rare and potentially fatal condition whereby the body’s sodium content drops leading to swelling of the brain.  There are many medical professionals that are refuting what Dr. McCartney wrote in the BMJ.  Rather than following the 8 X 8 rule, modifying water intake for each individual is recommended for good healthy and optimal performance.

There is no denying that water is important for life – approximately 60% of our bodies are made up of this important nutrient. Performance of every system in the body relies on water.  However, the 8 x 8 rule cannot be applied to everyone. There is no hard evidence that backs up the 8 X 8 rule for good health.  How much water you need for good health and performance depends on a number of factors including: your general health, your physical activity level and where you live.

Environmental conditions such as heat and humidity can affect the amount of water you should be drinking.  Sweating in extreme hot and humid conditions result in fluid loss.  Additionally, high altitudes can cause you to breathe faster, also resulting in fluid loss.  It is important to replenish the fluids lost during these conditions in order to maintain optimal performance of your body. Chronic and acute medical conditions may after your fluid levels as well.  It is important to speak with your doctor about fluid recommendations during times of illness.

Water is very important for athletic performance.  Athletes are always looking for ways to maximize performance by making changes to their diets.  However, water consumption is often over-looked.  Several litres of sweat can be lost during athletic performance and this fluid loss needs to be replenished in order to maintain your body’s hydration and temperature.  Sipping on water before, during and after exercise will help you to maintain your athletic performance.  These examples show that the 8 X 8 rule cannot be generalized across all populations.  Varying your intake of water based on different factors is the best way to ensure good health and optimal performance of all of your body systems.

Another negative aspect of the 8 X 8 rule is that it can be confusing because it only refers to “water” – it should refer to “fluid”.  All fluids that you drink and eat throughout the day, including those from fruits and vegetables, count towards your totals. In general, foods that you eat account for about 20% of your daily total.  If you eat a lot of fruits and vegetables such as watermelon and tomatoes, this percentage can climb even higher.  If you don’t like the boring taste of water, try adding fruits and vegetables with high water contents into your diet.  Fruits and vegetables can provide hydration as well as flavour.  Modifying your diet, by drinking water, eating fruits and vegetable with high water content and consuming other fluids that are low in sugar will help to ensure that you remain in good health.

Related Reading: High risk of not drinking enough water