BioChemistry, Nutrition

Understanding Hydration

Under ideal physiological conditions, there is an ample volume of fluid that provides the medium to all cellular existence within the body, and it is this driving force that allows for the transportation of all the essential nutrients throughout the body. It is in this environment when the body is properly hydrated, and there is a balance of fluid both inside the cells, as well as, outside the cells. 

Hydration is defined as the act of providing an adequate supply of water to every cell and tissue in the body. Water is the chief component of hydration and is the single most important nutrient to the body. It is crucial to the balance and the functioning of every bodily organ and system. Water exists in every cell and is essential for all biochemical reactions. Without water, the body would not survive.

Water is the largest component of the human body. In individuals of normal weight, the body is comprised of roughly 55% to 65% of water in weight. It is approximately 65% of the body weight in males and roughly 55% of the body weight in females. However, it can make up between 45 and 75% of the body weight depending on the differences in body fat. Water is roughly 45% of the body weight in an obese person and about 75% of the body weight in a lean person. This is explained by the fact that muscle is composed of roughly 85% water, where adipose tissue is less than 10% water.  Most other tissues and organs are roughly 70% water, including the heart, lungs, kidneys, liver and skin. The brain is about 85% water and bone is about 22% water.

The Importance of Hydration

    A sufficient supply of fluid is essential to good health and is required in the transportation of nutrients, elimination of waste products, lubrication of joints and tissues, facilitating digestion, reducing fatigue and enhancing athletic performance.


Aiding digestion and waste elimination.

Sufficient hydration is important to the flow of ingested food through the intestine and the removal of waste products from the blood. When dehydration occurs, the conditions are not ideal and the body cannot secrete ample amounts of digestive juices needed to facilitate the digestive process, nor is there a sufficient supply of fluid available to drive the circulatory system.


Improving athletic performance.

Proper hydration is critical during an athletic event. Maintaining good hydration levels during competition is essential in the body’s ability to regulate blood pressure and body temperature (thermoregulation). When dehydration occurs, the body’s cooling mechanism shuts down, which can lead to heat exhaustion or heatstroke. Furthermore, when dehydration occurs, neuromuscular activity decreases, which affects the rate and strength of each muscle contraction. This can lead to a loss of strength, reduced endurance and/or delayed muscular response/reaction. Conversely, when the body’s core temperature is cool and sufficient fluids are available, the neuromuscular activity increases and the muscular contractions become faster and stronger and performance is enhanced. In addition, when athletes drink large amounts of fluids (super-compensation) prior to competition, this too can improve athletic performance because it increases the body’s thermoregulatory response.

Other symptoms of dehydration include muscle cramps, dizziness, difficulty swallowing, headache or painful urination.


Reducing water retention.

Hydration levels directly correlate to the amount of water retained. There is a common misconception that drinking too much water leads to water retention. Contrary to this belief, when there is an adequate supply of water, the body is more efficient at removing waste products and excess water. When there is a constant supply of water, the body has no need to retain the water it receives, and it will readily excrete excess water through urination. However, when the body becomes dehydrated, it has a greater tendency to retain every drop of water it receives, as it slips into ‘survival mode’. 


Making weight.”

For competition, some athletes are required to ‘make weight’, in which the most common method is a rapid weight loss that leads to dehydration. Weight loss methods include starvation, fluid restriction, diuretics, laxatives or self-induced vomiting. These methods may be effective, but they may also pose health risks. Consequences of rapid weight loss, leading to dehydration include: reduced energy, mood swings, slowed metabolism, loss of muscle mass, reduced endurance and strength, and mental fatigue and exhaustion. Under extreme circumstances, these methods could result in collapse or death.


Protecting the joints.

Proper hydration is important to having healthy joints. It preserves synovial fluid in and around the joints, which provides cushion and lubrication to the joints and cartilage. When an adequate supply of water is available, the body can maintain synovial fluid production. When dehydration occurs, the amount of synovial fluid decreases, increasing the risk of injury. 


Reducing fatigue.

Good hydration is important to sustaining energy levels and minimizing fatigue. When the body becomes dehydrated, it is less efficient in the transportation of nutrients and the removal of waste products. This often leads to lethargy.


Weight management.

When the body is properly hydrated, it is more effective at maintaining its weight and avoiding excessive weight gain. When dehydration occurs, the kidneys cannot function properly; and therefore the liver must take over some of the kidney’s roles. When this occurs, the liver becomes less productive in its primary role of metabolizing stored fats.     

Keeping the Body Hydrated During Exercise

   The amount of water required depends on several factors, such as the initial level of hydration, the climate, or duration and intensity of an exercise. [Minimal amounts of water can be gained through metabolic activity (roughly 200 ml/day); therefore the majority of water replacement must come from the amount of fluids ingested.] 

Initial level of hydration.

Many individuals are not sufficiently hydrated. It is important to ensure proper hydration by drinking plenty of fluids, particularly prior to exercise. Hydration is crucial in helping maintain energy levels. Recommendation: Drink an abundance of water, initially, to ensure the body reaches a sufficient hydration level. Drink 4-8 ounces of fluid every 10-15 minutes.

The climate.

In hot and humid conditions, the body will perspire at increased rates. It is important to drink more fluids to compensate for this loss.

The duration and intensity of exercise.

The longer and more strenuous your physical activity is, the more fluid you will need to replenish the fluid lost. For training sessions less than one-hour, water is a sufficient means of hydration. For events that extend longer than one hour, it is recommended that individuals replenish with a carbohydrate/electrolyte replacement drink, instead of pure water.

Calories Burned/day

2,000 calories = 64-80 ounces

3,000 calories = 102-118 ounces

4,000 calories = 138-154 ounces

5,000 calories = 170-186 ounces

6,000 calories = 204-220 ounces

Another method used to estimate your daily water consumption is:

(Body Weight)  X  (0.6)  = Daily Water Intake (ounces)

How to know if you are properly hydrated.

* Individuals that are well hydrated will typically urinate about once every one and a half to two hours. 

* Urine should be clear and odorless.

Insufficient hydration is usually indicated when a person urinates only a few times a day or the urine is dark in color.  If this occurs, you should increase your water intake.

Hydrating for Competition

Pre-event hydration – It is recommended that individuals drink between 18–24 ounces of water two hours before an event. This gives the body ample time to excrete excess water prior to the start, (the recommended volume of water varies depending on body weight). It is then recommended that athletes drink another 18–24 ounces of water fifteen to twenty minutes just prior to the start. Athletes should avoid alcohol, coffee, or carbonated drinks prior to competition, as they possess diuretic properties and may lead to dehydration. Medications may also have an effect on hydration levels.

During event hydration – Drink 6–10 ounces every fifteen to twenty minutes for higher intensity exercises and 4–8 ounces every fifteen to twenty minutes for less intense exercises.


The type of fluids recommended are carbohydrate drinks because as time progresses, not only has water been lost from the body but carbohydrate stores have also been depleted. In order to replenish the carbohydrate stores and maintain the electrolyte balance, drinks such as Gatorade or Powerade are recommended over pure water. Carbonated or caffeinated drinks are not recommended, as they may inhibit absorption and lead to dehydration. Fruit juices are typically not sufficient at replacing the electrolytes lost through sweat.

Post-event hydration – It is recommended that you allow your body time to cool down and let your heart rate slow down and normalize before you rehydrate yourself. Once your heart rate has normalized, it is recommended to replenish yourself with a sports drink. There should be 10-16 ounces of replenishment fluid for every one pound of lost body weight, during exercise. It is also important to consume a balanced meal within one to two hours, post-event.


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