Ch 7 ppt

CHAPTER 7

Minerals

Eleanor D. Schlenker

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

2 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


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

6. Molybdenum

7. Chromium

8. Fluorine

9. Selenium

10. Cobalt

1. Iron

2. Zinc

3. Iodine

4. Manganese

5. Copper


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

Health & Medicine

Ch 7 ppt