Ch 7 ppt

CHAPTER 7
Minerals

Eleanor D. Schlenker

Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc.

Comparison of Vitamins
and Minerals
Vitamins
 Complex organic molecules that serve

primarily as coenzymes or regulators of body
metabolism
Minerals
 Simple elements with important roles in both
structure and function
 Excess of one vitamin or mineral cannot

remedy an existing deficit of another

Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 2

Roles of Minerals
Examples of Structural Functions
 Calcium and phosphorus: give strength to the

bones and body frame
 Iron: provides the core for the heme in

hemoglobin


Roles of Minerals – Cont’d
Examples of Metabolic Functions
 Ionized sodium and potassium: exercise

control over body water
 Iodine: necessary constituent of the thyroid

hormone that sets the rate of metabolism in
the cells


Concept of Bioavailability

 Bioavailability: proportion of an ingested
nutrient that is absorbed and can be used in
carrying out body functions
 Bioavailability is an important issue with
minerals


Concept of Bioavailability –
Cont’d
 Depends on many factors relating to both the
food source and the recipient:
 Binding substances in plants
 Gastric acidity
 Chemical form of the mineral
 Other foods in the same meal
 Body need


Classification
Major Minerals
 Seven minerals present in the body in larger

amounts
 Calcium, phosphorus, magnesium, sodium,
potassium, sulfur, and chloride


Classification – Cont’d
Trace Elements
 Ten minerals found in the body in smaller

amounts
 Iron, iodine, zinc, copper, manganese, chromium,
cobalt, selenium, molybdenum, fluoride
 All of these minerals have a defined role in
the body and must be supplied in the diet


Major Minerals
Calcium
 Present in the largest amount

 Calcium balance is applied at three levels:
1. Intake-absorption-excretion balance
2. Bone-blood balance
3. Calcium-phosphorus blood serum balance
 Calcium absorption ranges from 20% to 60%
of intake but decreases with age
 Absorption takes place in the small intestine,
primarily the duodenum


Calcium
Factors Increasing Absorption
 Vitamin D hormone

 Body need

 Dietary protein and carbohydrates

 Acid environment


Calcium – Cont’d
Factors Decreasing Absorption
 Vitamin D deficiency

 Fat malabsorption

 Fiber and other binding agents

 Alkaline environment


Calcium in the Bones
 Bones and teeth contain about 99% of total
body calcium
 As much as 700 mg of calcium enter and
leave the bones each day
 Immobility and osteoporosis cause losses


Calcium in the Blood
 Approximately 1% of total body calcium
circulates in the blood and other body fluids
 Blood calcium exists in two forms:
 Bound calcium
 Free ionized calcium


Control of Calcium Balance
 Calcium-phosphorus balance
 Serum calcium-phosphorus solubility products
 Three control agents work together to
maintain calcium balance:
1. Parathyroid hormone (PTH)
2. Vitamin D hormone (calcitriol)
3. Calcitonin


Physiologic Functions of Calcium
 Bone formation
 Tooth formation
 General metabolic functions
 Blood clotting
 Nerve transmission
 Muscle contraction and relaxation
 Cell membrane permeability
 Enzyme activation


Calcium: Clinical Applications

 Disruption of the physiologic and metabolic
functions of calcium is associated with:
 Tetany
• Decrease in serum ionized calcium
 Rickets and osteomalacia
• Deficiency of vitamin D hormone
 Resorptive hypercalciuria and renal calculi
• Risk of renal stones increases with the rise in urinary
calcium


Calcium and Health
 Bone disease
 Osteoporosis
 Drug regimens required to lower risk of fracture
 Prevention: high calcium intakes in infancy
through adolescence
 Metabolic disease
 Weight gain/body fatness
 Hypertension
 Cancer


Dietary Reference Intakes
for Calcium
Adequate Intake (AI)
 Youth ages 9 through 18: 1300 mg/day

 Men and women ages 19 to 50: 1000 mg/day

 After age 50: 1200 mg/day


Food Sources of Calcium
 Milk, cheese, yogurt
 Green leafy vegetables, broccoli, legumes,
nuts, and grains contribute calcium
 Oxalates and phytates compromise bioavailability
 Calcium-fortified soy milk, calcium-fortified
juices, and calcium-fortified cereals


Phosphorus
 Makes up about 1% of total body weight
 Absorption is regulated by the vitamin D
hormone calcitriol and phosphate carrier
proteins
 Kidneys are the main excretion route for
phosphorus and regulate serum phosphorus
levels
 Usually 85% to 95% of the plasma phosphate
filtered by the renal glomeruli is reabsorbed in
the renal tubules


Phosphorus – Cont’d
Bone-Blood-Cell Balance
 Approximately 80% to 90% of body

phosphorus is found in the skeleton and teeth
combined with calcium
 Normal range for serum phosphorus in adults

is 3.0 to 4.5 mg/dL


Bone-Blood-Cell Balance – cont’d
 Levels below 2.5 or above 5.0 mg/dL demand

immediate medical attention
 In its active phosphate form, phosphorus

participates in the structure and function of all
living cells


 Phosphorus balance is under the control of
two hormones that also control calcium:
1. Vitamin D hormone
2. PTH
 Phosphorus helps build bones and teeth
 Phosphorus is present in every living cell,
where it participates in overall metabolism


 General Metabolic Activities
 Absorption of glycerol and glucose
 Transport of fatty acids
 Energy metabolism
 Buffer system

 Clinical applications
 Recovery from diabetic acidosis
 Growth
 Hypophosphatemia
 Hyperphosphatemia


for Phosphorus

 1250 mg/day for those ages 9 to 18 years
 700 mg/day for all adults over age 18


Food Sources of Phosphorus
 Milk and milk products
 Lean meats
 Phosphorus-containing additives in
processed foods
 Soft drinks


Sodium
 Major cation in the extracellular fluids
 One of the most plentiful minerals in the body
 Easily absorbed in the small intestine; usually
no more than 2% remains to be excreted in
the feces
 Major route of excretion is through the kidney
under the control of aldosterone


Physiologic Functions of Sodium
 Water balance
 Acid-base balance
 Cell permeability
 Muscle action


for Sodium
 Adequate Intake (AI) is 1500 mg of sodium
(approximately 3800 mg of table salt) for
youth and young adults
 1300 mg sodium (approximately 3300 mg
table salt) for those ages 51 to 70 years
 1200 mg (approximately 3000 mg table salt)
for those ages 71 and older


for Sodium – Cont’d
 Tolerable Upper Intake Level for sodium is
2300 mg/day
 Sodium intakes above the recommended
level can lead to elevated blood pressure in
sodium-sensitive individuals
 Processed foods account for most high
sodium intakes


Potassium
 Twice as plentiful in the body as sodium
 Inside cells, where it guards intracellular
water
 Relatively small amount of potassium in
extracellular fluid is important for muscle
function


Potassium – Cont’d
 Dietary potassium is readily absorbed in the
small intestine
 Circulates in the gastrointestinal secretions
and is reabsorbed
 Principal route of excretion is the urine


Physiologic Functions of
Potassium
 Water balance
 Muscle action
 Carbohydrate metabolism
 Protein synthesis
 Control of blood pressure
 Acid-base balance


for Potassium
 AI is 4700 mg/day for all adults
 Lower intakes increase blood pressure and
bone loss


Food Sources of Potassium
 Legumes, whole grains, fruits such as
oranges and bananas, leafy green
vegetables, broccoli, potatoes, meats, and
milk
 Persons who eat many servings of fruits and
vegetables have potassium intakes of about 8
to 11 g/day


Magnesium
 Activates enzymes for energy production and
tissue building
 Role in normal muscle action
 Possible contributor to positive health effects
of DASH diet
 Decreases risk of metabolic syndrome
 May contribute to health benefits of whole
grains


for Magnesium

 RDA is 400 mg for men and 310 mg for women
ages 19 to 50
 RDA increases to 420 mg in men and 320 mg in
women over age 50


Food Sources of Magnesium
 Widespread in nature and unprocessed foods
 Whole grains are good sources
 Milk contains only a modest amount of
magnesium but is a major contributor to diets
in the United States
 Other sources include nuts, soybeans, cocoa,
seafood, dried beans and peas, and green
vegetables


Chloride
 Accounts for about 3% of total body mineral
content
 Found in the extracellular fluid, where it helps
control water balance and acid-base balance
 Fair amount of ionized chloride is found in the
gastrointestinal secretions


Sulfur
 Found in all body cells as a constituent of cell
protein
 Elemental sulfur forms sulfate compounds
with sodium, potassium, and magnesium


Sulfur – Cont’d
 Sulfur is also a part of the following:
1. Sulfur-containing amino acids
2. Glycoproteins in cartilage, tendons, and bone
matrix
3. Detoxification products formed by intestinal
bacteria
4. Organic molecules
5. Keratin in hair and nails


Essential Trace Elements
 An essential element is one required to
sustain life and whose absence brings death
 Have a required intake of less than 100
mg/day
 Two major functions
1. To catalyze chemical reactions
2. To serve as structural components of larger
molecules


Essential Trace Elements –
Cont’d
 Ten trace elements are essential in human
nutrition based on defined function and need

1. Iron 6. Molybdenum
2. Zinc 7. Chromium
3. Iodine 8. Fluorine
4. Manganese 9. Selenium
5. Copper 10. Cobalt


Iron
 Body iron is distributed in the following four
forms:
1. Transport iron
2. Hemoglobin/myoglobin
3. Storage iron
4. Cellular iron


Absorption of Iron
 Iron balance is controlled at the site of
absorption in the small intestine because
there is no system for iron excretion once it
has entered the body


Absorption of Iron – Cont’d
 Unabsorbed iron is excreted in the feces
 There are two forms of dietary iron:
1. Heme iron (found only in meat, fish, and poultry)
2. Nonheme iron (found in both plant and animal
tissue)


Absorption of Iron – Cont’d
 Nonheme iron is absorbed less efficiently
than the smaller heme iron molecule
 Ferric iron (Fe3+) must be reduced to the more
soluble ferrous form (Fe2+) before it can be
absorbed
 Gastric acid is required to reduce iron to the
ferrous form


Factors Favoring Iron Absorption
 Three factors favor absorption:
1. Body need
2. Ascorbic acid (vitamin C) or other acids
3. Animal tissues


Factors Hindering Iron
Absorption
 Five factors hinder absorption:
1. Binding agents such as phytates and oxalates
2. Low gastric acid
3. Infection
4. Gastrointestinal disease
5. Large amounts of calcium


Physiologic Functions of Iron
 Oxygen transport
 Cellular oxidation
 Immune function
 Growth needs
 Brain and cognitive function


Iron Deficiency Anemia
 Occurs in both developed and developing
countries and results in a hypochromic
microcytic anemia


Iron Deficiency Anemia – Cont’d
 Causes of iron deficiency anemia
 Low iron intake
 Blood loss
 Gastrectomy
 Malabsorption
 Chronic disease

 Iron deficiency anemia is a worldwide
problem


Dietary Reference Intakes for
Iron
 RDA is 18 mg/day for women ages 19 to 50
 8 mg/day for women ages 51 and over
 8 mg/day for men ages 19 and over
 27 mg/day for pregnant women
 Iron needs fall to 9 mg/day during lactation
because the menses are usually absent
during this period


Iron – Cont’d
 Individuals eating only plant foods are at
increased risk of iron deficiency because this
iron is less well absorbed
 Vegetarian adolescent girls need 26 mg/day


Iron Overload
 Adult men and women beyond the
childbearing years with lower iron
requirements are vulnerable to iron overload
with excessive intakes of highly fortified foods
or high-potency supplements
 Hemochromatosis
 Genetic disease
 High iron absorption regardless of liver stores


Food Sources of Iron
 Found in highest amounts in meat, fish,
poultry, eggs, dried peas and beans, and
whole grain and fortified breads and cereals
 Fortified grain products such as breakfast
bars contain from 1 mg to 24 mg of iron per
serving


Iodine
 Component of the hormone thyroxine
produced in the thyroid gland
 Thyroxine controls the rate of energy
metabolism in cells
 Body contains only 15 to 20 mg of iodine


Iodine – Cont’d
 Absorbed in the small intestine in the form of
iodides
 Iodides are then loosely bound to proteins
and carried by the blood to the thyroid gland
 Absorbed iodide not needed by the thyroid
gland is excreted in the urine
 Thyroid-stimulating hormone (TSH) directs
uptake of iodine by thyroid cells in response
to plasma thyroid hormone levels


Physiologic Function of Iodine
Thyroid Hormone Synthesis
 Major function of iodine is the synthesis of the

thyroid hormone thyroxine
 Thyroxine regulates cell oxidation and basal

metabolic rate (BMR)


Physiologic Function of Iodine –
Cont’d
Plasma Thyroxine
 Free thyroxine is secreted into the

bloodstream and bound to plasma protein for
transport to the cells


Iodine Deficiency Disorder
Goiter
 Visible as a great enlargement of the thyroid

gland
 Found in persons living where water and soil,

and in turn locally grown foods, contain little
iodine
 When iodine is not available, the thyroid

gland cannot produce a normal quantity of
thyroxine


Iodine Deficiency Disorder –
Cont’d
Cretinism
 Result of severe iodine deficiency during

periods of critical brain development
 Irreversible mental retardation and disability


Iodine
 RDA is 150 µg/day for both men and women
 220 µg/day during pregnancy
 290 µg/day during lactation


Food Sources of Iodine
 Seafood is rich in iodine
 Foods vary depending on the iodine content
of the soil and the iodine compounds used in
processing
 Iodized table salt is fortified with 1 mg iodine
per 10 g of salt


Zinc
 Participates in many metabolic activities as a
component of over 100 different enzymes
and a factor in growth
 Present in minute quantities in all body
organs, tissues, fluids, and secretions


Zinc – Cont’d
 Closely involved with deoxyribonucleic acid
(DNA) and ribonucleic acid (RNA)
metabolism and protein synthesis
 Necessary for tissue growth to progress at
normal rates


Zinc Deficiency
 Clinical problems stem from zinc deficiency:
 Hypogonadism
 Loss in taste and smell
 Impaired wound healing
 Impaired growth and development
 Impaired immune function
 Malabsorption


Zinc
 RDA is 11 mg for men and 8 mg for women
 Needs are lower for women because of their
generally smaller body mass
 Adolescent girls and older adults are most
likely to have low intakes
 Vegetarians have a higher risk for deficiency
 Phytates in plant foods interfere with absorption


Food Sources of Zinc
 Good sources of dietary zinc are seafood
(especially oysters), meat, and eggs
 Less rich sources are legumes and whole
grains


Copper
 Copper and iron have many characteristics in
common:
 Both are components of cell enzymes
 Both are involved in energy production
 Both participate in hemoglobin synthesis


Copper – Cont’d
 Copper occurs naturally in many foods, so
dietary deficiency is rare
Dietary Reference Intake
 Current RDA for copper is 900 µg/day (0.9

mg/day)


Manganese
 The adult body contains about 20 mg of
manganese distributed in the liver, bones,
pancreas, and pituitary gland
 Part of important cell enzymes


Manganese – Cont’d
 Deficiency has been reported in patients with
pancreatic insufficiency and protein-energy
malnutrition
Dietary Reference Intake
 2.3 mg/day for men and 1.8 mg/day for

women


Chromium
 Precise amount of chromium in the body is
not known
 Found in minute amounts in liver, soft tissues,
and bone
 Part of a protein complex that potentiates
insulin activity and helps move glucose into
cells
 No evidence that chromium picolinate is
effective as a body-building and weight-loss
supplement


for Chromium
 35 µg/day for men and 25 µg/day for women
ages 19 to 50
 30 µg/day for men and 20 µg/day for women
above age 50


Food Sources of Chromium
 Liver
 Cheddar cheese
 Wheat germ
 Whole grains


Cobalt
 Found in only minute traces in body tissues
with storage in the liver
 Cobalt is provided in the human diet only in
the form of vitamin B12


Selenium
 Deposited in all body tissues except fat
 Concentrations are highest in liver, kidney,
heart, and spleen
 Integral part of an antioxidant enzyme that
protects cells and lipid membranes from
oxidative damage
 Selenium and vitamin E spare each other


Selenium – Cont’d
 RDA for all adults is 55 µg/day

Food Sources
 Seafood, legumes, whole grains, lean meats,
and dairy products
 Vegetables contain only small amounts

 Amount depends on soil content


Molybdenum

 Enzyme cofactor in hydroxylation reactions
 RDA is 45 µg/day for men and women

Food Sources
 Richest sources generally include legumes,
whole grains, and nuts
 Animal products, fruit, and most vegetables
are poor sources


Fluoride
 Accumulates in the calcified tissues and
protects bones and teeth from mineral loss
(resorption)
 If fluoride is present when calcium-
phosphorus crystals are being formed, a
fluoride ion (F-) replaces a hydroxyl ion (OH-)
in the crystal
 Helps prevent dental caries and osteoporosis


Fluoride – Cont’d
 AI for men is 4 mg/day

 AI for women is 3 mg/day

Food Sources
 Fish, fish products, and tea contain the

highest amounts
 1 ppm added to most public water supplies


Water Balance
Body Water Distribution
 A woman’s body is about 50% to 55% water

 A man’s body is about 55% to 60% water

 Difference based on the fact that men have
greater muscle mass (higher in water
content) and women have more fat (lower in
water content)


Functions of Water
 Provides form and structure
 Fluid environment for chemical reactions
 Fluid for transport of nutrients and waste
 Helps control body temperature
 Fluid for dissolving medications


Water Input
 Preformed water in beverages
 Preformed water in food
 Metabolic water produced by cell oxidation


Water Balance
 Water leaves the body through the kidneys,
skin, and lungs and feces
 Intake and output must remain in balance to
sustain normal hydration levels
 Conditions of abnormal water loss or
inadequate access to water can lead to
dehydration
 Loss of body fluids is especially dangerous in
infants, whose bodies contain a higher
proportion of fluids

Water Needs
 Clinical situations influence water needs:
 Uncontrolled diabetes mellitus
 Cystic fibrosis
 High fiber intake
 High protein intake
 Intense athletic activity
 Impaired thirst in older persons
 Certain medications


Water Compartments
 Body water is divided into two major
compartments:
1. The water outside the cells—the extracellular fluid
compartment, which includes the blood plasma
and interstitial fluid
2. The water inside the cells—the intracellular fluid
compartment


Forces Controlling Water
Distribution

 The amounts of solutes or particles in solution
 The membranes that separate water
compartments


Influence of Electrolytes on
Water Balance

 Concentration of electrolytes is measured in
milliequivalents per liter (mEq/L)
 Ions carry electrical charges and are distributed
to maintain electroneutrality
 Potassium controls the amount of water in the
cells, and sodium controls the amount of water
outside the cells


Influence of Plasma Protein
on Water Balance
 Plasma proteins—albumin and globulin—
control the movement of water in and out of
the capillaries
 Capillary fluid shift mechanism allows water
and nutrients to flow into the cell and cell
waste to return to the capillary


Influence of Hormones on Water
Balance

 Antidiuretic hormone
 Aldosterone


Ch 7 ppt

Recomendados

Recomendados

Mais conteúdo relacionado

Mais procurados

Mais procurados (20)

Destaque

Destaque (20)

Semelhante a Ch 7 ppt

Semelhante a Ch 7 ppt (20)

Último

Último (20)

Ch 7 ppt