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  • Writer's pictureAnatomy Of Fitness


Updated: Nov 17, 2021

According to the Lay Press, 75% of Americans are chronically dehydrated. Dehydration can cause morbidity and mortality and has been the cause of many cases of hospital admissions. It may complicate many existing medical conditions by aggravating them. Dehydration can be prevented and treated provided it is diagnosed correctly and in time. Often, dehydration can lead to misdiagnosis of the actual cause and may lead to overtreatment. Once dehydration sets in, it severely deteriorates our performance and makes it increasingly difficult for our body to perform basic survival tasks. Let us probe what the functions of water in the human body are, what dehydration is, the signs of dehydration and how dehydration can be avoided.

WHAT are the FUNCTIONS of WATER in the Human Body?

Life cannot exist without water. Although water does not provide us with energy, it does undertake vital functions to sustain life. Without water, life may have never existed on earth. Our body gets water from the solids and liquids we ingest. Some organisms hydrate themselves from the water they get from solids alone. All major systems in our body depend on water. The National Academies of Sciences, Engineering, and Medicine determined that adequate daily fluid intake is about 3.7 litres of fluids for men and about 2.7 litres of fluids a day for women. However, depending on several factors like humidity, temperature, basal metabolic rate, body weight etc., the recommended fluid intake may vary from person to person. On average, we get 20% of the water from the solids we consume. There are thousands of functions for which water is required. Some of the most critical functions that water performs are:

  • Regulating body temperature through sweating.

  • Excreting waste in the form of urination, perspiration, and stools.

  • Supporting the creation of saliva.

  • Cushioning the joints and spinal cord.

  • Lubricating the eyes, ears, and nose.

  • Preventing constipation.

  • Aiding in digestion, nutrient absorption, and delivery.

  • Helping in the transportation of oxygen, hormones, enzymes, blood cells and platelets.

  • Supporting the cognitive function.


Dehydration occurs when the body lacks water to conduct its functions properly. Dehydration may set in if water loss is more than water intake. Excessive water loss can occur due to intense physical activity, high environmental temperature, high environmental humidity, or disease. Depending on the water lost, dehydration can be classified as mild (1% to 2% water loss), moderate (2% to 5% water loss) or severe (5% and above). We can tolerate a water loss of 3% to 4% to some extent. When water loss is between 5% to 8%, it starts affecting bodily functions and can cause dizziness or fatigue. A water loss of 10% and above can have grave consequences.

Death may occur if the water lost is over 15%.


The signs of dehydration are as follows:

  • Thirst (the first sign of dehydration).

  • Dry mouth, lips, eyes, and nose.

  • Reduced volume of urine.

  • Dark yellow colour urine.

  • Strong urine odour.

  • Urge to pass urine less than four times a day.

  • Headache.

  • Purple fingernails.

  • Tiredness.

  • Loss of appetite.


Here are the top 10 ways to avoid dehydration:

  1. Keep sipping fluids throughout the day (set reminders on your phone, use sticky notes as reminders, use apps that remind you to drink water etc.).

  2. Just like we carry our phones everywhere, carry a bottle of water everywhere.

  3. Keep track of your fluid intake (record manually or use apps to record your fluid intake).

  4. Have hydrating fruits and vegetables.

  5. If you feel dehydrated, try having as much water as you can or have an oral hydration solution at the earliest to avoid dehydrating further.

  6. As a preventive measure, drink more water if you suffer from vomiting or diarrhoea or are in a hot environment.

  7. Have lots of water before starting a steam/ sauna session or an intense exercise/ competition.

  8. Try to maintain body temperature to reduce water loss due to sweat. For example, avoid exercising in hot environments or choose early mornings/ late evenings for exercise, ensure ventilation and ambient temperature within the exercise environment, use breathable clothing.

  9. Avoid alcohol. It is toxic to our body. The body tries to expel alcohol by dissolving it in water and excreting it through the urine.

  10. If you have access only to seawater (and not freshwater), do not consume it. The kidneys will create more urine to clear the excess salt (from seawater) and worsen the condition. Also, never inject water into veins as it will cause red blood cell breakdown.

Key takeaways:

  1. Life cannot exist without water.

  2. All systems in our body are dependent on water.

  3. Dehydration occurs when the body lacks water to conduct its functions properly.

  4. Dehydration can be classified as mild (1% to 2% water loss), moderate (2% to 5% water loss) or severe (5% and above).

  5. Dehydration severely affects the ability to perform both mental and physical tasks.

  6. Dehydration can be easily prevented and corrected, provided correctly diagnosed in time.

We hope the article helped understand the functions of water in the human body, what dehydration is, the signs of dehydration and how to avoid dehydration.

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