Water (Lesson 9)

Karen Overstreet, Roy, Heli J.  |  1/29/2010 2:56:46 AM

What is Water?

Water is essential for the human body. Your body cannot store it and must have fresh supplies every day to perform virtually every bodily function. It is also one of six nutrients, just like protein, carbohydrates, fats, minerals and vitamins. Water contains zero calories. Chemically, water is a combination of the elements hydrogen and oxygen. The way these elements are put together makes water a solvent, meaning it can dissolve most nutrients, making them available for the body to use. Water in the body comes mainly from two sources: liquids and foods. A small amount of water is produced when the body metabolizes the food you eat (converts it to energy). Water is removed from the body in urine and feces, perspiration (sweating) and exhalation (breathing out air).

Most adult bodies are about 50%-75% water. This is equivalent to about 12 gallons of water. Young people and men have a slightly higher percentage of water in their bodies because they usually have more muscle and less fat. Muscle contains more water than fat. Babies have a high composition of water, about 75%.

Functions of Water

Water performs several functions in the human body. These include temperature regulation, waste removal, digestion, absorption, lubrication and transportation of nutrients.

Temperature Regulation – When the body becomes hotter than usual because of hard work, exercise, fever or exposure to heat, fluid is lost in the form of sweat (perspiration). This helps to cool the body, bringing the temperature closer to normal.

Waste Removal – Most waste products made by the body are water-soluble, so they can be excreted in the urine. The average person loses one to two liters of urine (mostly water) each day.

Digestion and Absorption – Nutrients from food are digested and absorbed into the bloodstream with the help of digestive juices. These juices are made mostly of water. Without the digestive juices, the body would not be able to get the nutrients from food.

Lubrication – Water lubricates the mouth in the form of saliva. This moistens the food so it can be swallowed easily. Saliva also begins the digestion process.

Transportation – Blood, which is about 85% water, carries the nutrients from digestion through the body and delivers them to the right places.

How Much Water Should You Drink?

Although some experts recommend drinking between 6-8 cups of water per day, there is not enough evidence to support this recommendation. The amount of water needed each day per individiual differs with their size, level of physical activity, the climate in which they live and many other factors. It is just recommended that you provide your body with enough water to replace the water lost in urine, feces, sweating and breathing and to keep it functioning regularly. Good ways to get enough water in the diet include drinking water, juices, milk, coffee and other beverages along with high-water-content foods, such as fruits and vegetables. Here in Louisiana we also inhale a lot of water as water vapor in the humid air. Individual water needs vary, depending on the activities the person participates in and other factors. Those who exercise, especially those who exercise in hot, humid weather, can lose up to a quart of water an hour. They need more water than non-exercisers. Other groups of people with increased fluid needs include:

  • Infants
  • Pregnant and lactating women
  • Elderly – The elderly can have a reduced sense of thirst and a reduced ability to conserve body water; therefore, it is important to encourage water consumption.
  • People with diarrhea or vomiting – These illnesses can cause dehydration, so it is important to increase fluid intake during these times.
  • People with fever – When body temperatures are elevated, extra fluid is lost and must be replaced.
  • Athletes or people doing hard physical labor
  • Air travelers
  • People on high-protein or high-fiber diets – Extra water is needed to help digest and absorb these nutrients.

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