Transcript Fundamentals of Nutrition

Section 1
Fundamentals of Nutrition
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Chapter 9
Water
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Objectives
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Describe the functions of water in the
body
Explain fluid balance and its
maintenance
Name causes and consequences of
water depletion
Give causes and consequences of
positive fluid balance
Describe the acid-base balance of the
human body
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Facts
Humans can live about 8 weeks without
food.
One can live only a few days without
water.
Water is in all body cells.
50-60% body weight of normal adults.
Percentage is highest in newborns;
decreases with age.
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Facts
Two basic compartments
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Intracellular fluid (ICF): within cells;
65% of total body fluid.
Extracellular fluid (ECF): outside cells;
35% of total body fluid.
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Divided into intravascular fluid (in blood
stream) and interstitial fluid (between
cells)
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Body Fluid Compartments
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Functions
Major component of blood plasma.
Solvent for nutrients and waste products.
Necessary for hydrolysis of nutrients.
Essential for metabolism.
Lubricant in joints and digestion.
Cools the body through perspiration.
Provides some mineral elements.
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Sources
Drinking water is the best source.
Beverages are second-best source.
Other sources include fruits, vegetables,
soups, milk, and gelatin desserts.
Energy metabolism produces water.
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Estimated Daily Fluid Intake for
an Adult
Ingested liquids
Water in foods
Water from oxidation
Total
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1,500 ml
700 ml
200 ml
2,400 ml
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Fluid and Electrolyte Balance
Electrolytes are measured in
milliequivalents (mEq/L).
Sensible (noticeable) water loss is water
lost through urine.
Insensible (unnoticeable) water loss is in
feces, perspiration, and respiration.
Waste products of metabolism excreted in
the form of urine (500 ml of water each
day).
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Fluid and Electrolyte Balance
Solute: substance dissolved in a solution.
Osmosis: water flows from the side with
the lesser amount of solute to the side with
the greater solute concentration.
Sodium, chloride, and potassium maintain
the balance between intracellular and
extracellular fluids.
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Fluid and Electrolyte Balance
Potassium is the principal electrolyte in
intracellular fluid.
Sodium is the principal electrolyte in
extracellular fluid.
Osmolality measures particles in a
solution.
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Fluid and Electrolyte Balance
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Fluid and Electrolyte Balance
When electrolytes in extracellular fluid are
increased, ICF moves to the ECF to
equalize the concentration of electrolytes
on both sides of the membrane. Reduces
the amount of water in the cells.
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Fluid and Electrolyte Balance
Hypothalamus stimulates pituitary gland to
excrete ADH (antidiuretic hormone).
ADH causes kidneys to reabsorb water.
Thirst causes healthy person to drink
fluids.
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Fluid and Electrolyte Balance
When sodium in ECF is reduced, water
flows from ECF into cells, causing cellular
edema.
Adrenal glands secrete aldosterone, which
triggers kidneys to increase the amount of
sodium reabsorbed.
When the missing sodium is replaced in
the ECF, excess water moves back to the
ECF and edema is relieved.
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Fluid and Electrolyte Balance
Amount of water use varies, depending on
age, size, activity, environmental
temperature, and physical condition.
Average adult requirement is 1 ml for
every kcal in food consumed.
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Stop and Share
How many glasses of fluid would be
required for an adult eating 1,800
kcal/day?
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Stop and Share
1 ml × 1,800 kcal = 1,800 cc
1,800 cc  240 oz = 7.5 glasses of water
It is recommended that adults drink eight
8-ounce glasses of fluid a day.
Youth, fever, diarrhea, unusual
perspiration, and hyperthyroidism increase
the requirement.
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Dehydration
Amount of water in the body is inadequate.
Caused by inadequate intake or abnormal
loss.
Loss can occur from severe diarrhea,
vomiting, hemorrhage, burns, diabetes
mellitus, excessive perspiration, excessive
urination, or the use of certain medications
such as diuretics.
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Dehydration
Symptoms of dehydration include low
blood pressure, thirst, dry skin, fever, and
mental disorientation.
As water is lost, electrolytes are also lost.
Treatment involves replacement of
electrolytes and fluids.
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Dehydration
10% loss can cause serious problems.
Blood volume and nutrient absorption are
reduced, and kidney function is upset.
20% loss can cause circulatory failure and
death.
Infants are at high risk for dehydration
when fever, vomiting, and diarrhea occur.
Treatment involves IV fluids.
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Dehydration
Thirst sensation lags behind the body’s
need for water, especially in the elderly,
children, athletes, and the ill.
Feeling thirsty is not a reliable indicator of
when the body needs water.
Fluids should be drunk throughout the day
to prevent dehydration.
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Dehydration
Failure to replace water lost through
perspiration could lead to one of the four
stages of heat illness:
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Heat fatigue
Heat cramp
Heat exhaustion
Heat stroke
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Signs of Dehydration
Health history reveals inadequate intake of
fluids
Decrease in urine output
Weight loss
Eyes appear sunken
Tongue has increased furrows and fissures
Oral mucous membranes are dry
Decreased skin turgor
Changes in neurological status
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Excess Water Accumulation
Positive water balance–more water taken
in than excreted; edema results.
Hypothyroidism, congestive heart failure,
hypoproteinemia, some infections, some
cancers, and some renal conditions can
cause water retention because sodium is
not being excreted normally. Fluids and
sodium may then be restricted.
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Acid-base Balance
Regulation of hydrogen ions
Acid gives off hydrogen ions
Base picks up hydrogen ions
Acidic substances–pH 1 to 7
Alkaline substances–pH 7 to 14
pH 7 is considered neutral
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Acid-base Balance
Blood plasma–pH 7.35 to 7.45
Intracellular fluid–pH 6.8
Kidneys maintain acid-base balance
What a person eats affects the acidity not
of the body but of the urine.
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Buffer Systems
Regulate hydrogen ion content in body
fluids
Mixture of a weak acid and a strong base
Normal buffer system–ratio of base to acid
20:1
Carbonic acid and sodium bicarbonate
forms the body’s main buffer system.
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Buffer Systems
Carbonic acid moves easily to buffer a
strong alkali, and sodium bicarbonate
moves easily to buffer a strong acid.
Amounts are easily adjusted by the lungs
and kidneys to suit needs.
End products of metabolism are carbon
dioxide and water, and together they can
form carbonic acid.
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Buffer Systems
The medulla oblongata in the brain causes
the breathing rate to increase if the amount
of carbon dioxide is more concentrated
than it should be. This increases the rate at
which the body rids itself of carbon
dioxide.
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Buffer Systems
Excess sodium bicarbonate is
excreted via the kidneys.
The kidneys can excrete urine from
pH 4.5 to pH 8.
The pH of average urine is 6.
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Acidosis and Alkalosis
Renal failure, uncontrolled diabetes
mellitus, starvation, or severe diarrhea can
cause acidosis.
Alkalosis can occur when the body has
suffered a loss of hydrochloric acid from
severe vomiting or has ingested too much
alkali, such as too many antacid tablets.
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Stop and Share
A client is unhappy with her low sodium,
fluid restricted diet. How can the health
care professional best help the client?
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Stop and Share
Discuss realistic ways of planning menus
for her and with her.
Base menus on good nutrition, the client’s
normal habits and desires.
Review former diet with the client.
Point out high-salt and high-liquid foods
and present alternative foods in a positive
manner.
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Conclusion
Water is a component of all tissues.
Solvent for nutrients and body wastes.
Provides transport for both.
Essential for hydrolysis, lubrication, and
maintenance of normal temperature.
Best sources are water, beverages, fruits,
vegetables, soups, and water-based
desserts.
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Conclusion
Dehydration may result from lack of water.
Positive water balance is an excess
accumulation of water in the body.
Acid-base balance is the regulation of
hydrogen ions in the body.
Healthy people have intricate maintenance
systems for fluid, electrolytes, and acidbase balance.
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