1.7 Water

What is water in relation to human nutrition?

An essential nutrient needed in the largest amount by the body compared to any other nutrient

What percentage of the human body is made up of water?

Roughly 60 percent water

What is water intoxication?

A rare condition where excessive water is ingested or urine production is reduced diluting blood sodium concentration and causing hyponatremia

What is dehydration?

A condition where fluid output exceeds fluid intake

What are the symptoms of dehydration?

Thirst dry skin dry mucous membranes rapid heartbeat low blood pressure and weakness

What is extracellular fluid?

Fluid outside the cell accounting for plasma lymph and interstitial fluids

What is intracellular fluid?

Fluid inside the cell

What is intercellular or interstitial fluid?

Fluid located between cells

What is insensible fluid loss?

Unmeasurable fluid losses by the body during normal respiration and evaporation through the skin

What is the estimated daily volume of insensible fluid loss in an adult?

Up to 700 mL per day with about 350 mL through respiration and 350 mL through skin evaporation

What is sensible fluid loss?

Measurable fluid losses that normally occur through the kidneys as urine and through the gastrointestinal tract in feces

What does potable water mean?

Water that is safe for drinking

What is osmosis?

Movement of water across a semipermeable membrane from an area of lower solute concentration to an area of greater concentration

What is simple diffusion?

Simple transport where small molecules pass through a membrane from an area of higher concentration to lower concentration without energy or carrier proteins

What is passive diffusion?

A form of simple diffusion utilizing a channel protein to pass small molecules like water across a membrane without energy

What is facilitated diffusion?

Transport requiring a carrier protein to move molecules from higher to lower concentration without energy

What is active transport?

Transport requiring a carrier protein plus energy to move a nutrient across a membrane against an energy gradient

What are the main physiological functions of water in the body?

Carrying nutrients and waste products maintaining structure of large molecules aiding metabolic activities acting as a solvent lubricant cushion amniotic fluid temperature regulator and volume maintainer

How does water function in relation to large molecules like proteins and glycogen?

Maintains the physical structure of large molecules

What role does water play for joints and the spinal cord?

Acts as a lubricant and cushion around joints and the spinal cord

What role does water play during pregnancy?

Makes up much of the amniotic sac surrounding and protecting the fetus

What is the recommended general intake ratio of water per calorie of expended energy?

Approximately 1.0 to 1.5 mL per calorie of expended energy

How much daily water does a person expending 2000 calories per day require?

Approximately 2000 to 3000 mL of water daily

What is the Adequate Intake AI of total water for adult men?

3700 mL per day

What is the Adequate Intake AI of total water for adult women?

2700 mL per day

What is the adult fluid requirement formula based on body weight?

35 mL per kg of body weight

What is artesian water?

Water drawn from a well

What is carbonated water?

Water containing carbon dioxide gas forming bubbles

What is distilled water?

Water that has been vaporized and condensed leaving it free of dissolved minerals

What is filtered water?

Water treated by carbon filters to reduce lead or reverse osmosis to remove lead arsenic and microorganisms

What defines hard water?

Water with a high calcium and magnesium content

What defines mineral water?

Water from a spring or well that naturally contains at least 250 parts per million ppm of minerals

What is natural water?

Water obtained from a spring or well that is certified as safe and sanitary

What is public water?

Water from a municipal or county water system that has been treated

What is purified water?

Water treated by distillation or other physical or chemical process that removes solids

What defines soft water?

Water with a high sodium or potassium content

What is spring water?

Water originating from an underground spring or well

What is well water?

Water drawn from groundwater by tapping into an aquifer

Why are minerals added back to bottled water after purification?

To enhance the taste of the water

Which minerals are added back to purified bottled water to enhance taste?

Calcium magnesium and sodium

What is the typical pH of purified water prior to refortification?

Near or below 6.5 making it more acidic and soft

What substance is added to bottled water to raise the pH to neutral or slightly alkaline?

Sodium bicarbonate

What is the typical pH range of most bottled waters?

Between 6.5 and 8.5

What is the Adequate Intake AI of water for infants up to 6 months of age?

700 mL per day

What is the Adequate Intake AI of water for infants aged 7 to 12 months?

800 mL per day

What condition in infants can result from water deficits?

Hypernatremic dehydration

What are symptoms of water intoxication in infants?

Hyponatremia restlessness nausea vomiting diarrhea and polyuria

Why should plain water in excess amounts be avoided in young infants?

Risks diluting serum electrolytes

Why should an infant bottle taken to bed contain only water?

To prevent tooth decay

How much fluid should athletes consume 2 to 3 hours before exercise?

14 to 22 ounces of fluid

How much fluid should athletes consume every 15 to 20 minutes during exercise?

6 to 12 ounces of fluid

How much fluid should athletes consume post exercise per pound of body weight lost?

16 to 24 ounces of fluid per pound lost

Why should sports drinks containing sodium be consumed during long duration athletic events lasting over 90 minutes?

To replenish electrolytes lost in sweat and prevent hyponatremia

Should thirst be used as an indicator for when an athlete should drink fluid?

No thirst should not be used as an indicator to drink

What percentage of body weight loss during a sweat rate test indicates a need for more fluid intake during exercise?

More than 2 percent of body weight lost

Which hormone secreted by the posterior pituitary regulates water excretion by the kidneys?

Vasopressin or antidiuretic hormone

Which hormone secreted by the adrenal glands signals the kidneys to retain sodium and water?

Aldosterone

What enzyme released by the kidneys converts angiotensinogen to angiotensin I when blood pressure is low?

Renin

What enzyme in lung capillary beds converts angiotensin I to angiotensin II?

Angiotensin converting enzyme ACE

What is the volume of ultrafiltrate produced daily by the kidneys?

About 180 liters of ultrafiltrate per day

What is the average daily volume of urine excreted by the human kidneys?

About 1.5 liters per day

What defines oliguria regarding daily urine output?

Urinary volume of less than 500 mL per day

What is evaporation of water during cooking?

The process of liquid turning into a gaseous state necessary for drying foods

At what temperature does water boil and turn to steam at sea level?

212 degrees F

What percentage of whole milk consists of water?

About 88 percent water

What percentage of fresh vegetables consists of water?

More than 80 percent water

What percentage of fresh fruits consists of water?

About 75 to 95 percent water

What percentage of melons consists of water?

Nearly 90 percent water

What physiological changes regarding blood volume occur during pregnancy?

Blood volume expands by about 50 percent by the end of pregnancy

How does progesterone affect water reabsorption in the gastrointestinal tract during pregnancy?

Decreases GI motility leading to an increase in water reabsorption