What is Water? (Lesson 9)

Karen Overstreet, Roy, Heli J., Stanciu, Catrinel E., Gentry, Ramona S.  |  3/2/2005 9:23:39 PM

Dirty water fountain


Drink a lot of water every day

What is Water?

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 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 is made of more water than fat is.) 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 place.

How Much Water Should You Drink?

Sedentary adults need nine to 12 cups of fluids each day. Some of this is from foods that are high in water such as fruits, vegetables, juices, milk, coffee and other drinks, and of course water. 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. Exercisers, 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.

How to Get Enough Water - Tips to Try

1. Keep a glass or bottle of water with you during the day so you can sip from it often. When you travel, bring your water bottle along!

2. Start some of your meals with soup. Soup provides plenty of fluid and can curb your appetite if you're trying to lose weight. Be careful of the sodium levels in canned soups though! If you are on a low-salt diet, choose soups that are lower in sodium.

3. Drink more water, milk and juices and fewer soft drinks.

4. Drink when you feel thirsty and even when you don't feel thirsty! When exercising or doing other hard physical labor, drink water every 15-20 minutes, even if you're not thirsty.

5. Increase your fluid intake if your diet is high in fiber, protein or salt.

Dehydration occurs when there is not enough water in your body. Dehydration can be acute, as from illness or from an intense exercise such as a hard workout. Dehydration can be chronic, too, resulting from your not getting over a period of time enough water each day to replace your daily water losses. Dehydration is defined as a 1% to 2% loss of body weight caused by fluid losses. Dehydration of 2% loss of body weight results in impaired physiological and performance responses.

Acute dehydration can happen easily when a person is sick (vomiting, diarrhea or fever) and losing more fluid than normal. Young children and elderly people are especially susceptible to dehydration. If an elderly person gets the flu, fever or diarrhea, the amount of water in the body can decrease within days or even hours. Elderly people have less water in their bodies to begin with (because they have more fat and less muscle than younger people), so they can become dehydrated quickly.

Some signs of dehydration include headache, thirst, loss of appetite, fatigue, increased temperature, heavy breathing, faster pulse rate, flushed skin, dry mouth and eyes, burning sensation in the stomach, dizziness and dark urine with a strong odor.

If you have a baby sick with a fever, diarrhea or vomiting, check to see if he wets his diaper. If he doesn't, he is dehydrated. A baby can become dehydrated quickly.Call the doctor's office right away when your baby gets any of these symptoms. Assess your own hydration status by evaluating the color of your urine. It should be pale yellow or straw colored if you are well hydrated. If your urine becomes dark with a strong odor, you need more water. You may also have a medical condition with that symptom

Soft Drinks

Although you can get water from other fluids besides plain water, it is recommended that juice or milk be consumed instead of soft drinks. Soft drinks usually contain caffeine (a stimulant), a natural diuretic. Caffeine can cause a person to lose more water by having to urinate more frequently. The more caffeine you drink, the more water you lose through urination. Caffeine can cause your body to lose more calcium through excretion. Too much caffeine can have negative effects, such as jitters, anxiety, insomnia (inability to sleep) or a faster heart rate. Soft drinks are also high in sugar and can contribute to the feeling of dehydration.

Water Questions and Answers

What is hard water and soft water?

Hard water is water with a high calcium and magnesium (minerals) content. Soft water has a high sodium (mineral) content. Most cities have soft water or soften their water by removing the calcium and magnesium and adding sodium. People usually prefer soft water because it doesn't leave a mineral buildup on appliances or scum in the tub. These are caused by the minerals in hard water. Soft water doesn't have the metallic taste that hard water can have, another reason it is usually preferred.

Should you buy bottled water?

In urban areas, tap water is just as safe as bottled water because of government regulations; so, it is a matter of personal preference as to whether you should buy bottled water. In some rural areas, there may be a higher amount of lead (a mineral) in the tap water. Also, some homes have lead water pipes, so the water will contain more lead. If this is the case, pregnant women and families with young children may need to buy bottled water because it does not contain lead. Tap water usually contains chlorine and some people do not like its taste in the water. Therefore, they may choose to buy bottled water because it doesn't contain chlorine and tastes better. Bottled water may lack the fluoride supplied by tap water. Fluoride is important in helping form healthy teeth and in keeping your teeth healthy. Check with your local LSU AgCenter office regarding lead or other concerns about your water. If your water has off flavors, you might also explore possibilities of filtering.

Why does tap water sometimes have a bad odor?

The bad odor, described by some as a rotten egg odor, is caused by the amount of sulfur (a mineral) in the water.


Water is necessary for life. Humans cannot survive long without it. The average human body is composed of 50%-75% water. Most people should drink at least six to eight cups of fluids each day to replace what is lost in urine, feces, sweat and exhalation. Sedentary adults need nine to 12 cups of fluid daily. Some people need more water, especially those who exercise, perform hard physical labor or have various illnesses. The functions of water include temperature regulation, waste removal, digestion, absorption, lubrication and transportation of nutrients.


Rate This Article:

Have a question or comment about the information on this page?

Innovate . Educate . Improve Lives

The LSU AgCenter and the LSU College of Agriculture