Chapter 13
Trace Minerals
Chapter Outline
I. What Are Trace Elements? *Trace elements are minerals that the body needs in small
amounts. They are involved in a variety of structural and regulatory functions and are
found in both animal and plant foods.
A. Why are trace elements important?
B. Other characteristics of trace elements
II. Iron. *Iron functions in oxygen transport as part of hemoglobin and myoglobin. It is also
an enzyme cofactor, important for immune function, and involved in normal brain function.
A. Functions of iron (Figure 13.5)
1. Oxygen transport
2. Enzymes
3. Energy metabolism
4. Immune function
B. Regulation of iron in the body. *Iron balance is regulated through absorption;
absorption increases when body status is low, and decreases when stores are
normal. Meat, vitamin C, and stomach acid tend to increase nonheme iron
absorption; phytate, phenolic compounds, and high doses of other minerals tend to
decrease iron absorption.
1. Iron absorption (Figure 13.6)
a. Process of iron absorption
b. Effect of the body’s iron status on iron absorption
c. Effect of GI function on iron absorption
d. Effect of the amount and form of iron in food
e. Dietary factors that enhance iron absorption
f. Dietary factors that inhibit iron absorption
g. Iron absorption and vegetarianism
h. Iron transport and storage
i. Iron turnover and loss
C. Dietary recommendations for iron. *Recommendations for iron intake consider
the amount needed to replace daily losses, and the bioavailability of iron from a
typical mixed diet. Due to regular iron losses via menstrual bleeding, women of
childbearing age need more iron than adult men do.
D. Sources of iron (Figure 13.10). *The best sources of iron are meats. Enriched
and whole grains are significant sources in the American diet.
E. Iron deficiency and measurement of iron status. *Iron deficiency is the most
common nutritional deficiency worldwide. The most severe stage of deficiency,
following reduction of iron stores and transport iron, results in anemia.
1. Progression of iron deficiency (Table 13.2)
F. Iron toxicity. *Iron toxicity can result from acute ingestion of high doses, or from
chronic excessive iron absorption. Accidental iron overdose is a leading cause of
poisoning deaths of children under 6 in the United States.
1. Iron poisoning in children
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2. Hereditary hemochromatosis
Key terms: hemochromatosis, ferrous iron, ferric iron, heme, myoglobin, cytochromes,
myelinization, transferrin, ferritin, heme iron, nonheme iron, polyphenols, transferrin
receptor, hemosiderin, transferrin saturation, protoporphyrin, hematocrit, microcytic
anemia, iron overload
III. Zinc. *Zinc is a cofactor for numerous enzymes and is crucial for normal growth,
development, and immune function. It is found in protein-rich foods, particularly red meat.
A. Functions of zinc (Figure 13.12)
1. Zinc and enzymes
2. Zinc’s role in nucleic acid metabolism
3. Zinc and the immune system
4. Zinc and vision
5. Zinc and gene regulation
6. Other zinc functions
B. Regulation of zinc in the body
1. Zinc and absorption
2. Dietary factors that inhibit zinc absorption
3. Zinc transport and distribution
4. Zinc homeostasis and excretion
C. Dietary recommendations for zinc
D. Sources of zinc (Figure 13.15)
E. Zinc deficiency (Table 13.3). *Zinc deficiency results in poor growth, impaired
taste, delayed wound healing, and impaired immune response.
F. Zinc toxicity
Key terms: hypogonadism, geophagia, galvanized, metalloprotein, metallothionein,
hemodialysis, Crohn’s disease, acrodermatitis enteropathica, Wilson’s disease
IV. Selenium. *Selenium functions as part of the glutathione peroxidases, important
antioxidant enzymes. Good sources of selenium are organ meats and seafood. Deficiency of
selenium appears to be rare, but has been described in an area of China called the Keshan
region.
A. Functions of selenium (Figure 13.16)
B. Regulation of selenium in the body
C. Dietary recommendations for selenium
D. Sources of selenium (Figure 13.17)
E. Selenium deficiency
F. Selenium toxicity
Key terms: Keshan disease, selenomethionine, selenocysteine, hypothyroidism, cretinism,
total parenteral nutrition (TPN)
V. Iodine. *Iodine is necessary for the formation of thyroid hormones, which regulate
metabolic rate and body temperature. Much of the iodide in the American diet comes from
iodized salt. Iodine deficiency results in goiter. If severe deficiency occurs during
pregnancy, the child may be born with cretinism.
A. Functions of iodine
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B. Iodine absorption and metabolism
C. Dietary recommendations for iodine
D. Sources of iodine (Figure 13.19)
E. Iodine deficiency
F. Iodine toxicity
Key terms: goiter, triiodotyronine (T3), thyroxine (T4), thyroglobulin, thyroid-stimulating
hormone (TSH), goitrogens
VI. Copper. *Copper functions in many enzyme systems including those involved with
antioxidant mechanism, iron utilization, and immune function. The richest food sources of
copper include organ meats, shellfish, nuts and seeds, peanut butter, and chocolate.
A. Functions of copper
B. Copper absorption, use, and metabolism
C. Dietary recommendations and food sources for copper (Figure 13.20)
D. Copper deficiency. *Copper deficiency results in anemia, decreased numbers of
white blood cells, and bone abnormalities.
E. Copper toxicity
Key terms: Menkes’ syndrome, ceruloplasmin, chelation therapy
VII. Manganese. *Manganese functions in conjunction with several enzyme systems. The
best food sources include tea, coffee, nuts, cereals, and some fruit. Manganese deficiency
and toxicity are uncommon; toxicity is usually associated with exposure through manganese
mines.
A. Functions of manganese
B. Manganese absorption, use, and homeostasis
C. Dietary recommendations and food sources for manganese (Figure 13.21)
D. Manganese deficiency
E. Manganese toxicity
Key terms: amyotrophic lateral sclerosis (ALS), multiple sclerosis, mineralization
VIII. Fluoride. *Fluoride promotes mineralization of bones and teeth and protects the teeth
from caries. Water is a major source of fluoride, due to either naturally high content or
added fluoride. Fluorosis is the result of excessive fluoride intake and results in the mottling
of the teeth.
A. Functions of fluoride
B. Fluoride absorption and excretion
C. Dietary recommendations for fluoride
D. Sources of fluoride
E. Fluoride deficiency, toxicity, and pharmacological applications
Key term: fluorosis
IX. Chromium. *Chromium functions in the normal use of insulin to promote glucose use.
Rich sources of chromium are mushrooms, dark chocolate, prunes, nuts, asparagus, whole
grains, wine, brewer’s yeast, and some beers. Chromium deficiency in humans is difficult to
assess, and toxicity of inorganic chromium is unlikely.
A. Functions of chromium
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B. Chromium absorption, transport, and excretion
C. Dietary recommendations and food sources for chromium
D. Chromium deficiency
E. Chromium toxicity
Key term: albumin
X. Molybdenum. *Although the body contains only about 2 milligrams of molybdenum, it is
an important enzyme cofactor. Good food sources are peas, beans, and some breakfast
cereals. Molybdenum deficiency and toxicity are both rare.
A. Molybdenum absorption, use, and metabolism
B. Dietary recommendations and food sources for molybdenum
C. Molybdenum deficiency and toxicity
XI. Other Trace Elements and Ultratrace Elements. *Ultratrace minerals are those required
in extremely small amounts; the specific function of many of these nutrients is unknown.
Some ultratrace minerals are arsenic, boron, nickel, silicon, and vanadium.
A. Arsenic
B. Boron
C. Nickel
D. Silicon
E. Vanadium
Key term: silicosis
Classroom Activities
ACTIVITY 1: TRIVIA
See Activity 1 in Chapter 1 for an explanation on implementing trivia in the classroom.
TRIVIA QUESTIONS
What are trace elements?
ANSWER: Trace elements are essential minerals found in a large variety of animal and
plant foods that have both regulatory and structural functions in the body.
The dietary requirements for each of the trace elements are less than _______ mg per day.
ANSWER: 100
What animal organ is a particularly good source of trace minerals?
ANSWER: liver
This is the fourth most abundant mineral in the earth’s crust, yet its deficiency is the most
common nutrient deficiency in the world.
ANSWER: iron
What does iron transport throughout the body?
ANSWER: oxygen
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What is the name for a heme protein that transfers electrons in the electron transport chain
through the alternate oxidation and reduction of iron?
ANSWER: cytochromes
Where is more than 80 percent of the body’s functional iron found?
ANSWER: red blood cells (hemoglobin)
Give two examples of good sources of heme iron.
ANSWER: beef, clams, oysters, liver, pork, lamb, legumes
What is the mineral that is a cofactor for numerous enzymes and is crucial for normal
growth, development, and immune function?
ANSWER: zinc
Zinc deficiencies may develop a condition that is also seen with vitamin A deficiency. What
is this condition?
ANSWER: night blindness
What is the trace element that functions as a part of the glutathione peroxidases, which are
important antioxidant enzymes?
ANSWER: selenium
What is the congenital condition often caused by severe iodine deficiency during gestation?
ANSWER: cretinism
What condition results from an iodine deficiency?
ANSWER: goiter
What are the best food sources of iodide?
ANSWER: seafood
What trace element functions in many enzyme systems including those involved with
antioxidant mechanisms, iron utilization, and immune function?
ANSWER: copper
True or False? Copper deficiency occurs most often in young adults.
ANSWER: False. Preterm infants most often have copper deficiency because they have low
copper stores at birth and have a rapid growth rate.
ACTIVITY 2: WHAT WOULD YOU RECOMMEND FOR EILEEN?
The following case study can be introduced before the review of iron. If students have read
the chapter, they should be able to identify some major changes Eileen could make to
minimize the side effects from her iron-deficiency anemia.
Case Study
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Eileen is 19 years old and has iron-deficiency anemia. She constantly feels fatigued, has
headaches, and feels cold most of the time. Eileen is within her ideal body weight range and
likes to be physically active. She is willing to do whatever it takes to make herself feel
better.
Eileen doesn’t mind including animal products in her diet, but has heard that these
foods actually decrease iron absorption. As a result, Eileen has identified plant foods that
are high in iron and started including them in her diet. At every meal, Eileen does not put
sugar in her tea because she knows it is not nutrient dense. In addition, when Eileen cooks,
she uses nonstick stainless steel pans so she doesn’t have to use a lot of fat in her food
preparation. Eileen usually has a glass of orange juice in between her meals to increase her
vitamin C intake and makes sure to take a calcium supplement with her dinner meal.
As you can see, Eileen is trying to be healthy and decrease the effects of her irondeficiency anemia. However, there are many things Eileen could do to better utilize the iron
she does consume. What would you recommend for Eileen?
ANSWERS
 She needs to start including heme iron food sources in her diet, such as meats, poultry,
and fish, as these iron sources are more bioavailable.
 Eileen needs to decrease her consumption of tea because this contains polyphenols that
significantly decrease iron absorption.
 Eileen could use a cast-iron pot when cooking foods to increase the iron content.
 Because Eileen is within her ideal body weight range and is physically active, she can
cook with fat in moderation without worry. Everyone needs a certain amount of fat in
his or her diet. (She could use olive or canola oil.)
 Eileen should have the glass of orange juice at her meals because vitamin C increases
the absorption of nonheme iron.
 Although the long-term significance of calcium supplementation on iron absorption is
unclear, to be safe, Eileen should take her supplement alone at bedtime rather than with
meals.
ACTIVITY 3: TRACE ELEMENT TOXICITIES AND DEFICIENCIES
The following can be used as a pre-quiz to the trace minerals chapter or as a homework
assignment.
Directions: Match the trace element with the proper toxicity or deficiency described below.
Answers may be used more than once.
Trace Elements
a. chromium
b. copper
c. fluoride
d. iron
e. iodine
f. selenium
g. zinc
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1. ____ Hemochromatosis is a genetic disease that can lead to severe organ damage,
diabetes, heart disease, cirrhosis, and even death.
2. ____ Crohn’s disease can impair the absorption of this trace element leading to
symptoms of poor growth and impaired immune response.
3. ____ This deficiency predisposes a person to Keshan disease.
4. ____ A deficiency of this trace element can cause a chronic enlargement of the thyroid
gland.
5. ____ Chronic consumption can cause brittle hair and nails, and eventual loss of hair and
nails.
6. ____ A deficiency in this trace element causes fatigue, weakness, headaches, and an
abnormally low body temperature.
7. ____ Menkes’ syndrome is an extremely rare genetic disorder that results in a failure to
absorb this trace element into the bloodstream.
8. ____ Low intake of this trace element increases the risk for dental caries.
9. ____ Wilson’s disease is a rare genetic toxicity disorder that impairs the excretion of this
trace element in bile, causing toxic accumulation in the liver, brain, kidneys, and
eyes.
10. ____ A side effect from this deficiency may be decreased insulin-mediated glucose
uptake by cells, decreased insulin sensitivity, elevated blood glucose, and insulin
and blood lipid abnormalities.
ANSWERS
1. d
2. g
3. f
4. e
5. f
6. d
7. b
8. c
9. b
10. a
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