Water

The Nutrient Most Essential to Life

Water Requirements

The body needs more water per day than

any other nutrientOne can only survive a few days without

waterIn less than a day, a lack of water alters

the body’s chemistry and metabolism

Functions of Water

Water makes up ≈60% of an adult’s body weight

Water is found in– Blood vessels

– Cells

– Chemical structure of cells, tissues, organs

• Water participates in many chemical reactions

Why Is Water the MostIndispensable Nutrient?

Delivers nutrients and removes waste fromcells

Water is a, nearly, universal solvent Dissolves amino acids, glucose, minerals, etc.

for transport

Why Is Water the MostIndispensable Nutrient?

Water is the body’s cleansing agent– Nitrogen wastes, produced during metabolism,

dissolve in blood and must be removed before they build up to toxic levels

– Kidneys filter these wastes from the blood and, mixed with water, excrete them as urine

Why Is Water the MostIndispensable Nutrient?

Water plays a role in thermoregulation– Sweat cools the body

Meaning that the skin is a major route of water loss

Some loss via exhaled breath and fecesBlood routed through capillaries in the skin

gets rid of excess heatThe cooled blood then flows back to the

body’s core

The Body’s Water Balance

Water balance– Water intake needs to equal water loss– Otherwise dehydration or water intoxication can occur

The Body’s Water Balance

• Dehydration– Water loss– Progression of symptoms: thirst → weakness → exhaustion and delirium → death

The Body’s Water Balance

Water intoxication– Dangerous dilution of body fluids resulting from excessive water ingestion– Symptoms: headache, muscular weakness, lack of concentration, poor memory, loss of appetite

--Rarely leads to death

The Body’s Water Balance

• Body’s water content– Varies by pounds at a time• Especially in women who retain water during menstruation• High-salt meal leads to water retention– Water is lost over a 1-2 day period as the sodium is excreted• Fluctuation in water weight does not reflect gain or loss of body fat

How Much Water Do INeed to Drink in a Day?

• DRI meets ≈ 80% of day’s need for water– Men: 13 cups of fluid from beverages anddrinking water– Women: 9 cups of fluid from beverages anddrinking water– Remaining water need is met from consumedfoods– Body produces water from the breakdown ofenergy-yielding nutrients

Beverages

The best source of water is water!Other beverages are good sources of

fluids too Milk and Juice

Some beverages actually dehydrate the body more and do not count toward daily fluid intake Soda, Coffee, Tea, and Alcohol

Consumer Corner:Bottled Water

• ≈1 in 15 households use bottled water– 250-10,000 times the cost of tap water– Not safer than tap water• Test of 1,000 bottles of 103 brands– ≈33% contaminated with bacteria, arsenic, or synthetic organic chemicals– ≈25% of bottled water is drawn from the tap