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How much water should I drink?

Most people function in a dehydrated state and are unaware of the importance of adequate hydration. Both performance and well being are inseparably associated with an adequate supply of water, just like all the other functions of your body.

The importance of water

We need six nutrients to function properly: carbohydrates, proteins, fats, minerals, vitamins and water. Approximately 68% of the body is comprised of water and a constant supply is required as all bodily functions depend on the balance of body water. The human physiology needs water for heart function, regulation of body temperature, blood pressure, metabolic functions of all cells and lubrication of the joints. Fluids are needed in the blood to transport glucose to the working muscles and eliminate metabolic bi-products. Muscle tissue alone is over 70% water. Vital functions of the body are seriously compromised when an individual is dehydrated.


Dehydration is defined as the loss of fluid from all of the body's fluid compartments. It occurs when the rate of fluid lost is greater than the rate of fluid replaced. Loss is at its greatest during physical activity, especially in hot weather. Without adequate fluid intake, a progressive increase in core temperature causes early muscle fatigue and the risk of heat exhaustion. Symptoms of dehydration can range from a mild headache, sluggishness to even more serious complications like collapse and unconsciousness. Elevated body temperatures and heart rates, inability to sustain aerobic exercise and mental confusion may also be part of the fatigue. Exhaustion may occur even if the body has lost only 1% of body weight due to water loss.

Dehydration: The science bit

A common reaction to drinking water is to wait until you are thirsty. This is a signicant mistake as the body is already dehydrated by the time thirst is apparent. Thirst sensation is triggered by a high concentration of sodium (a part of salt) in the blood. When you sweat water is lost from the blood so the remaining blood becomes more concentrated with sodium. In hot and humid conditions the blood vessels near the skin open to allow the transfer of excess body heat to the environment, so the balance of your internal temperature can be maintained. This causes a reduction in stroke volume (the amount of blood ejected by the heart per beat) and venous return. At any given pace, heart rate will increase and elevate higher than normal as the cardiovascular system attempts to maintain cardiac output to meet the oxygen demands in our muscles. When someone is dehydrated the circulatory system is heavily burdened and cannot meet physiological demands. As a result, the blood volume decreases and the heart has to work much harder to dissipate the internal heat produced with exercise.


Science has discovered that the total amount of water lost each day is approximately two litres in sedentary adults in cool environments. Although the daily minimum requirement is about 8-10 cups just to maintain ef?cient bodily functions, regular exercise and hot/humid weather compounds the need to increase ?uid intake. This brief table re?ects the differences in ?uid requirements brought on by activity and environment:

Person Environment Fluid replacement (daily)
Sedentary cool 2-3 litres
Active cool 3-6 litres
Sedentary warm 3-5 litres
Active warm 5-10 litres

To consume this much water on a daily basis may seem daunting. However, try to drink water continuously in small amounts as the process of re-hydration can be very slow.

Fluid intake before exercise or a fitness competition

Athletes and those exercising should drink adequate fluids throughout the 24 hours prior to an event or workout. Exercisers should start drinking early, and at regular intervals, in order to consume water at a rate sufficient to replace that which will be lost through sweating.

Fluid intake during exercise

Water consumption is equally important for someone who enthusiastically power-walks or works out in the gym as it is for the seasoned athlete. Fluids consumed should be cooler than ambient temperature as this ensures more rapid absorption through the stomach into the body. If an event/session is greater than an hour long then isotonic sports drinks can be effective. If they are not available, then water is still acceptable (spring, mineral or ?ltered).

Fluid intake after exercise

It is difficult to completely replace all of the water lost during exercise. Generally speaking, exercising individuals lose between 0.5 and 1.5 litres of sweat in 1 hour of exercise. In the majority of cases, the average person is definitely dehydrated when he/she has finished exercising. Try to consume 8-10 ounces every 15 minutes after exercise.

Types of drink

Remember that soft drinks and alcohol have no nutritional value whatsoever, except to provide around 150+ calories of refined sugar! This sugar may temporarily refuel the muscles with carbohydrates, but the natural sugars in fruit juices perform the same task and also replace the potassium lost in sweat. Juices with Vitamin C, a healing and antioxidant nutrient, will promote more efficient post exercise recovery and reduce muscle soreness. Sports drinks are good during a long workout because their low carbohydrate levels are easier to absorb. After exercise slightly diluted juice or water are your best choices. Note also that alcohol is a diuretic, causing more water loss and greater dehydration.

Hydration is vital and everybody engaging in exercise, at all levels and intensities, should work to increase their water intake. You will be very surprised at how much better you will feel and perform just by drinking more water.

This article is courtesy of Alan Gordon

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