Water

Water

Charles Lohman

Water• Water – water constitutes about 60% of an adult’s body

weight– body composition influences how much of the body’s

weight is water because there is more contained in lean tissue and less in fat

– water is an essential nutrient, more important than any others

– the body needs more water each day than any other nutrient

– you can survive only few days without water, where a deficiency of other nutrients may take weeks, months or even years to develop

Water and Body Fluids

• Water and the body’s life processes– water carries nutrients and waste products

throughout the body– water maintains the structure of large molecules– water participates in metabolic processes– water acts as a lubricant and cushion – water aids in the regulation of body temperature– water maintains blood volume

Water Balance and Recommended Intakes

• Water Intake– thirst and satiety influence water intake in response to

changes in the mouth, the hypothalamus and nerves– when there is inadequate water intake the blood becomes

concentrated, the mouth becomes dry, and the hypothalamus initiates drinking behavior

– when water intake is excessive, the stomach expands and stretch receptors send signals to stop drinking

– when too much water is lost from the body and not replaced, dehydration develops

– water intoxication is rare, but can occur with excessive water ingestion and kidney disorders that reduce urine production


• Water Sources– obvious dietary sources of water are water itself and other

beverages– nearly all foods contain water– fruits and vegetables contain about 90% water– meats and cheeses contain about 50% water– water is also generated during metabolism

• Water Losses– the body must excrete at least 2 cups of water each day as

urine, which is enough to carry away waste products generated by the body’s metabolic processes

– water is also lost from the lungs as vapor and from the skin as sweat


• Water Recommendations– about 8 to 12 cups which is based on a person who expends

2000 kcalories a day– total water includes not only drinking water, but water in other

beverages and foods as well– people who are physically active or live in hot environments

may need more– beverages currently represent over 20% of the total energy

intake in the United States– most people would well to select water as their preferred

beverage– some research suggests that people who drink caffeinated

beverages lose a little more fluid than when drinking water because caffeine acts as a diuretic


• Health Effects of Water– drinking water may protect against urinary stones and

constipation– even mild dehydration seems to interfere with daily tasks

involving concentration, alertness, and short term memory– the kind of water a person drinks may also make a

difference to health; hard water vs soft water– hard water has high concentrations of calcium and

magnesium which may benefit hypertension and heart disease

– soft water contains sodium and potassium which may aggravate hypertension and heart disease

Education

Water