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Understanding Nutrition
Chapter 13
The Trace Minerals
By A. Fellah
Trace Minerals
 Essential mineral nutrients found in the body in <5 g (microminerals). Required in minuscule quantities.
 Food Source: Depend on soil and water composition and on how food are
processed.
 Deficiency:


Mild deficiencies are easy to overlook.
Results of a deficiency is failure of children to grow and thrive.
 Toxicities:

Some are toxic at intakes not far above the estimated requirements.
 Interactions:

Common and often lead to nutrient imbalances, a slight manganese
overload may aggravate an iron deficiency.
Iron
 Essential nutrient, vital to many of the cell’s activities.
 Iron Roles in the Body:
 The reduced state, iron has lost two electrons (ferrous).
 The oxidized state, iron has three lost electrons (ferric).
 Can work as cofactor to enzymes involved in oxidationreduction reactions.
Cofactor: is a mineral element that works with an enzyme to
facilitate a chemical reaction.
Most of the body’s iron is found in two proteins:
 Hemoglobin in the red blood cells and myoglobin in the
muscle cells.
 Iron helps accept, carry, and then release oxygen.
 Iron Absorption and Metabolism
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Mucosal ferritin: receives Iron from GI tract and store it in
mucosal cells.
Mucosal transferritin: receives iron from mucosal ferritin and
transferred to blood transferritin.
Blood transferritin: transfers the iron to the rest of the body.
Intestinal cells are replaced every 3 days. These cells can
either deliver iron when needed or dispose of it when intakes
exceed needs.
Heme iron: the iron-holding part of the hemoglobin and
myoglobin, (well absorbed iron).
Iron Routes in the Body
Most iron is recycled. Some is lost with body tissues and must be
replaced by eating iron-containing food.
Heme and Nonheme Iron in Foods
 Absorption-Enhancing Factors:

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MFP factor: a factor associated with the digestion of Meat,
Fish, and Poultry that enhances nonheme iron absorption.
Vitamin C (ascorbic acid).
Citric acid and lactic acid from foods and HCl acid from
stomach.
Sugars.
 Absorption-Inhibiting Factors:

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Phytate and fibers (grains and vegetables).
Oxalates (spinach).
Calcium and phosphorus (milk).
EDTA (food additive).
Tannic acid (and other polyphenols in tea and coffee).
Iron Absorption
Factors that enhance nonheme iron absorption.
Iron Absorption
Average percentage of iron absorbed from selected foods by healthy adults.
Iron Absorption from Food
People absorb more iron from foods and supplements when body
stores of iron are low than when stores of iron are high.
Foods That Promote Iron Absorption
This chili dinner provides several factors that may enhance iron absorption:
heme and nonheme iron and MFP from meat, nonheme iron from legumes,
and vitamin C from tomatoes.
The combination of heme iron, nonheme iron, MFP, and vitamin C helps to
achieve maximum iron absorption.
Iron and Oxygen
Iron’s role in carrying oxygen to cells and carbon dioxide away
from them by way of the bloodstream. Fe++ represents charged
particles of iron. The charge is neutralized when iron combines
with oxygen or carbon dioxide.
Iron Deficiency
 Iron-deficiency anemia: severe depletion of iron stores
that results in low hemoglobin and small, pale, red
blood cells.
 High risk for iron deficiency:
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Women in their reproductive years.
Pregnant women.
Infants and young children.
Teenagers.
 Blood Losses:
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The iron content of blood is ~0.5 mg/100ml blood.
A person donating a pint of blood (~500ml) losses ~2.5 mg
of iron.
Incidence of iron deficiency.
Assessment of Iron Deficiency

Stages of iron deficiency:
• Iron stores diminish. Measures of serum ferritin reflects
iron stores.
• Transport iron decreases. Transferritin increases.
• Hemoglobin and hematocrite values decline. Increase in
hemoglobin precursor, erythrocyte protoporhyrin.
 Iron Deficiency and Behavior:
 Slightly lowered iron levels impair oxidation of pyruvate.
 Reduction of energy to work, think, play, sing, ……..
 Iron Deficiency and Pica:
 An appetite for ice, clay, paste, and other nonfood
substances.
 Pica: a craving for nonfood substances.
 Geophagia: referring to clay eating.
 Pagophagia: referring to ice craving.
Iron Deficiency Anemia
Normal Red Blood Cells
Iron Deficiency Anemia-Small microcytic and
pale hypochromic cells
contain less hemoglobin.
Iron Toxicity
 Iron Overload: toxicity from excess iron.

Hemochromatosis: a hereditary defect in iron
metabolism characterized by deposits of iron-containing
pigment in many tissues, with tissue damage.

Effect 1.5 millions in USA.

Repeated blood transfusions.

Massive doses of supplementary iron.

Hemosiderosis: a condition characterized by the
deposition of hemosiderin in the live and other tissues.

Some symptoms are similar to iron deficiency: apathy and
fatigue.
Placebo Pills
If you were three years
old, could you tell
which “pills” are candy
and which are the iron
supplements?
Overdoses of iron
supplements are a
leading cause of
accidental poisoning in
young children. (The
iron supplements are
the lightest green in
color.)
 Iron Recommendations and Sources:

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Diet provides 6-7 mg/ 1000 kcalories
For men: recommended daily intakes = 8 mg.
For women: recommended daily intakes = 18 mg.
Women receives only 12-13 mg/day, not enough until after
menopause.
Iron in Food:
• Meat, fish, and poultry contributes the most.
• Legumes and eggs are also good sources.
• When the label on a grain product says “enriched,” it
means iron and several B vitamins have been added.
Contamination Iron
An old-fashioned iron skillet adds iron to foods.
Zinc
 It is a versatile trace element required as a cofactor by more
than100 enzymes.
 All cells contain zinc but highest in muscles and bones.
 Zinc Roles in the Body:

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Metalloenzymes: enzymes that contain one or more
minerals as part of their structures.
Assists in immune function and in growth and development.
Participates in the synthesis, storage, and release of
insulin.
Interacts with platelets in blood clotting, affects thyroid
hormone function, and influence behavior and learning
center.
Involved in production of vitamin A (retinal).
 Zinc Absorption and Metabolism
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Zn absorption varies from 15-40%, if more is needed more is
absorbed.
Fiber and phytate bind zinc, thus limiting its bioavialabity.
Metallothionein:
a sulfur-rich protein that avidly binds
with metals.
• Synthesized in the intestinal cells helps to regulate zinc
absorption.
• Holds zinc until needed by other body tissues.
Enteropancreatic Circulation:
• The circulatory route from the pancreas to the intestine
and back to the pancreas.
Albumin: blood protein carrier
Transferrin: zinc binding protein.
• Iron may interfere with zinc absorption.
Zinc’s Routes in the Body
Notice the enteropancreatic circulation of zinc from the intestines
through the blood to the pancreas and back to the intestines.
 Zinc Deficiency:

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Hinders digestion and absorption, causing diarrhea.
It impairs the immune response causes infections of the GI
tract which worsen malnutrition.
Chronic deficiency damages the central nervous system.
Disturbs thyroid function and the metabolic rate.
 Zinc Toxicity:

50-450 mg of zinc may cause vomiting, diarrhea, headaches,
exhaustion.
 Zinc Recommendation:
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
11 mg/day adequate for women.
Requirements for infants and children are relatively higher
than for adults.
Zinc Deficiency
The Egyptian man on the
right is an adult of average
height.
The boy on the left is only 4
feet tall, like a 7-year-old in
USA.
The growth retardation,
known as dwarfism, is
ascribed to zinc deficiency
17 year
old male
Food Sources of Zinc
Zinc is highest in protein-rich foods such as oysters, beef, and
poultry; and legumes and nuts.
Iodine
 Traces of the iodine ion (iodide) are indispensable to life.
 Iodine converted to iodide in GI tract.
 Iodide Role in the Body:

An integral part of the thyroid hormone that regulates body
temperature, metabolic rate, reproduction, growth, blood cell
production, and nerve and muscle function.
 Iodine Deficiency:

Goitrogen: a thyroid antagonist found in food; causes toxic
goiter.
• Found in cabbage, kale, brussels sprouts, cauliflower,
and broccoli.

Cretinism: a congenital disease characterized by mental
and physical retardation and commonly caused by maternal
iodine deficiency during pregnancy.
An enlargement
of the thyroid
gland due to an
iodine deficiency,
the thyroid gland
enlarges--a
condition known
as “simple” goiter
Iodine deficiency
 Iodine Toxicity:

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Excessive intake can enlarge the thyroid gland.
Excessive intake during pregnancy, is especially damaging
to the developing infant.
The upper level is 1000 mg/day for an adult.
 Iodine Sources:
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In coastal areas, seafood, water and iodine-containing sea
mist are high in iodine.
Iodization of salt has eliminated the widespread misery .
 Iodine Intake:

Average consumption exceeds recommendation.
 Iodine Recommendation:

In a minuscule amount.
Selenium
 It is essential mineral
 It is one of the body’s antioxidant nutrients, working as a part of
the enzyme glutathione peroxidase.
 Glutathione peroxidase prevents free-radical formation.
 Deficiency:

Associated with a heart disease (Keshan disease) prevalent
in China where the soil and foods are lacking selenium.
 Selenium poor soil correlates with a high incidence of cancer.
 Intake:

people living in regions with selenium-poor soil may still get
enough selenium.
 Toxicity:
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High doses ( a mg or more daily) are toxic.
Vomiting, diarrhea, loss of hair and nails, and lesions of the
skin.
Copper
 The body contains ~100 mg of copper.
 Roles in the Body:
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Constituent of several enzymes.
All enzymes involve in reactions that consume oxygen or
oxygen radicals.
Enzymes catalyze the oxidation of ferrous iron to ferric iron.
Copper’s role in iron metabolism make it a key factor in
hemoglobin synthesis.
Two coppers and one zinc containing enzymes participate in
the body’s natural defense against free radicals.
Needed in the metabolic reactions related to the release of
energy.
 Copper Deficiency and Toxicity:
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Deficiency is rare.
Vitamin C interfere with copper absorption and can lead to
deficiency.
Two rare genetic disorders
• Menkes disease: the intestinal cells absorb copper, but
cannot release it into circulation, causing a lifethreatening deficiency.
• Wilson’s disease, copper accumulates in the liver and
brain, creating a life-threatening toxicity. Control it by
reducing copper intake, using chelating agents, and
taking zinc supplements.
 Copper Recommendation and Intakes:
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Legumes, whole grains, nuts, shellfish, organ meats, and seeds.
Over half is absorbed, and major route of elimination is the bile.
Manganese
 20 mg, mostly in the bones, liver, kidneys, and pancreas.
 It acts as a cofactor for many enzymes.
 Manganese-containing metalloenzymes assist in urea synthesis,
the conversion of pyruvate to a TCA cycle compound, and the
prevention of damage by free radicals.
 Deficiency:
 rare.
 The requirements are low.
 Phytates inhibits its absorption.
 High intake of iron and calcium limit manganese absorption.
 Toxicity:
 Occur from environment contaminated with manganese than
from food.
Fluoride
 Present in all soils, water supplies, plants, and animals.
 Roles in the Body:
 During mineralization, calcium and phosphorus form
hydroxyapatite crystals. Fluoride replaces the OH portions
forming fluorapatite, which makes stronger bones and more
decay resistant teeth.
 Fluoridation and Dental Caries:
 Fluoridation of drinking water to concentration of 1ppm offers
the greatest protection against dental caries.
 Toxicity:
 Occurs when fluoride concentration reach 150 ppm.
 Symptoms: nausea, vomiting, diarrhea, abdominal pain, and
numbness or tingling of the face and extremities.
Excessive Fluoride Intake
"Mottled
teeth" result from an excessive intake of fluoride
during childhood.
Fluoridation of Water in the U. S.
Fluorosis
Discoloration and pitting of tooth enamel caused by excess
fluoride during tooth development.
Chromium
 It is essential mineral, participates in carbohydrate
and lipid metabolism.
 Cr+++ ion is the most effective form.
 Roles in the Body:
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Helps maintain glucose homeostasis by enhancing the
activity of insulin.
Lacking chromium, a diabeteslike condition may develop.
 Recommendations and Intakes
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Present in variety of foods.
Sources: unrefined foods, liver, brewer’s yeast, whole
grains, and nuts.
Molybdenum
 It acts as a working part of several metalloenzymes.
 Required in minuscule amounts, 0.1 ppm of body
tissue.
 Sources:
 Legumes, breads and other grain products, leafy
green vegetables, milk, and liver.
 Toxicity:
 It is rare, but has been reported in animal studies.
 Symptoms: kidney damage and reproductive
abnormalities.
Summary
 Each of the trace minerals fulfills a vital role in
the body.
 A deficiency or an excess could be fatal.
 Well-balanced diets normally supply the right
amount of each trace mineral to maintain
health.
 Each of the following trace minerals are
reviewed: iron, zinc, iodine, selenium, copper,
manganese, fluoride, chromium,
molybdenum, and others.