The Nutrient Most Essential to Life Water The Nutrient Most Essential to Life

Water Requirements The body needs more water per day than any other nutrient One can only survive a few days without water In 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 Most Indispensable Nutrient? Delivers nutrients and removes waste from cells Water is a, nearly, universal solvent Dissolves amino acids, glucose, minerals, etc. for transport

Why Is Water the Most Indispensable 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 Most Indispensable 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 feces Blood routed through capillaries in the skin gets rid of excess heat The 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 I Need to Drink in a Day? • DRI meets ≈ 80% of day’s need for water – Men: 13 cups of fluid from beverages and drinking water – Women: 9 cups of fluid from beverages and drinking water – Remaining water need is met from consumed foods – Body produces water from the breakdown of energy-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