Water in Our Diets

Water is an essential nutrient for the human body. Even though humans don't look it, more than half our bodies are made up of water. Water has many different uses in the body and can be obtained from many sources.

Recommended Intake

• According to the Mayo Clinic, an average adult loses about 2 liters of water a day. The body loses the majority of this water through urine, but it also loses about 4 cups of water through moisture in breath, sweat and stool. If a person fills up a glass that contains 8 oz. of water and drinks eight of these a day, he replaces the lost fluids. Food also contains water, and about one-fifth of a person's daily water can come from food. An indication that a person takes in enough water is that his urine is pale or colorless. Drinking more than 3 liters of water a day can be dangerous, as this affects the body's electrolytes.

Percentage of Water in the Body

• An average adult male's body is 60 percent water. Different parts of the body have different levels of water. For example; the brain is 70 percent water, lungs are 90 percent water, bone is more than 20 percent water, but fat only has 10 percent water. As women's bodies generally have more fat than men's bodies, women are therefore only about 55 percent water.

Water's Role in the Body

• Water plays several essential roles in the human body. Blood is 83 percent water, and is the means by which nutrients move around the body to areas that need them. Water molecules are also essential materials for biochemical reactions. Water also acts as a carrier for waste product excretion through urine, breath, sweat and stool.

  The high percentage of water in our tissues, such as the 75 percent concentration of water in muscle tissue, allows our bodies to absorb physical shock quite well. The presence of water also allows us to control our body temperature because water heats up and cools slowly. Sweating also cools us in hot conditions.

Dietary Sources of Water

• All beverages contain water. Good beverages for hydration include water itself, milk, sodas, juices and non-caffeinated hot drinks. Most food also contains some level of water. For example; cucumber, lettuce, watermelon and other watery foods are good sources. Crisp vegetables such as celery are up to 90 percent water. Even meat can be more than half water by weight. Vegetables and fruit that don't appear to contain water may still contain a high percentage of water. For example; grains are about one-third water.