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The average adult will normally lose approximately 2 quarts of water per day through perspiration, waste removal and other functions.  Add hot weather and/or enough exercise to break a sweat and the amount of water needed to stay hydrated quickly increases. The body loses water via the skin by perspiration, kidneys by urine, the lungs by exhaled water vapor, and the intestine by feces.  

The human body is roughly 60% water.  Human lungs are 90% water, muscles are 75%, bones are 22%, blood is 83%, and the brain is 75% water.  Some functions of water include regulation of body temperature, carrying nutrients and oxygen to cells, helping to convert food to energy, protecting and cushioning vital organs, and cushioning joints.


Seventy-five percent of Americans are chronically dehydrated.  This statistic likely also applies to half of the world’s population.  A mere 2 percent drop in body water can trigger fuzzy short-term memory, trouble with basic math, and difficulty focusing on a computer screen or on a printed page.  

Water is often called the forgotten nutrient since many people take it for granted, but water is essential to life.  Humans can live with less than enough food for weeks, months, and even years, but take away water and humans will last just a few days.  


Water makes up about 60 percent of the average adult’s weight.  It is the medium the human body uses for nearly every activity it performs. ·Since water is so important, its balance is delicately monitored by a number of mechanisms throughout the body.  If the body has just 2 percent less than it requires, the person will feel fatigued. A 10 percent shortfall can produce significant health risks and a week without water can be fatal.

Because of the importance of water the brain signals humans to drink when the sodium concentrations in the blood become too high or when blood volume drops too low.  Unfortunately, by the time this thirst mechanism kicks in, the body is already in the beginning stages of a water deficit. That’s why nutritionists recommend drinking before the feeling of thirst is recognized.  This is particularly critical for the elderly population because as humans age they become less sensitive to their thirst mechanism. At the same time, the percentage of body fluid drops, so it becomes easier to dehydrate faster.  In addition, young children are also at a higher risk for dehydration. The thirst mechanism in small children is not yet fully developed, nor are they always able to recognize when they are thirsty. Therefore, parents and caregivers should encourage children to drink water often, especially when at play or on hot days.  Water needs vary with each individual, but in general, nutritionists suggest the following formula: take your body weight and divide it in half. This is the amount of ounces per day you should be drinking of water. For example, a 140 pound human should drink 70 ounces of water per day.


Some of the benefits of drinking water include better digestion and metabolism, better workouts, better glycogen storage (energy stored in the muscles), weight loss, healthier skin, less cramps and sprains, less likely to get sick, relief from fatigue and/or headaches, and reduced risk of certain cancers.  

A reusable water bottle that can be refilled throughout the day will help to increase a person’s water intake and get them in to the habit of always having water available.


Lisa Landman is a fitness and health guru. Learn more about her professional work or check out her Twitter!