1. NUTRITION for a Changing World
Jamie Pope, Steven Nizielski, and Alison McCook
NUTRITION
for a Changing World
FIRST EDITION
Chapter 14
Trace Minerals
Small Amounts with Big Importance
© 2016 by W. H. Freeman and Company & Scientific American

2. Chapter 14
Objectives
Describe the major functions of copper, fluoride, iodine, iron, selenium, and zinc in the body (see slides)
Identify the general properties of trace minerals
Describe how the use of iodine and the production of thyroid hormone are controlled
Describe the symptoms of deficiency and toxicity of copper, fluoride, iodine, iron, selenium, and zinc (see slides for any italicized content related to deficiency and toxicity)
Identify at least two dietary sources of copper, iodine, iron, selenium, and zinc (see slides for any italicized content – most trace minerals found across food groups)
Discuss the dietary sources of heme and non-heme iron and the factors that affect their absorption

3. Iodine deficiency disrupts thyroid function and can cause goiter.
During World War I, 64.4% of people in Michigan showed signs of a goiter
Enlargement of thyroid gland
Soils deficient in iodine
Added iodine to table salt
Iodine deficiency remains one of the most important public health issues globally.
During World War I many men, women, and children of the Goiter Belt (as many as 64.4% of people in some parts of Michigan) were showing signs of a goiter, an enlargement of the thyroid gland. Many military recruits were too unhealthy to serve in the war efforts. The soils of the Great Lakes, Appalachians, and Northwestern regions of the United States are poor in the trace mineral iodine, which the body needs to make thyroid hormones.

4. Trace minerals differ from major minerals in all of the following ways, EXCEPT:
Their daily requirement is less than 100 milligrams
Their safe range of intake is more narrow
They are found in smaller amounts in the body
They are less essential in human health
They include iodine and iron
Answer is D.
As noted for chapter 13, I teach both chapters 13 and 14 in one class (my class meets for 2 consecutive class periods per week). The polling slides precede content coverage as set up as a competition. Can move them as warranted.

5. The amount of trace minerals required in the diet and found in the body is significantly less than for major minerals.
Include iron, iodine, zinc, copper, selenium, molybdenum, fluoride, manganese, and chromium
Daily requirement <100 mg/day
The body requires significantly less of trace minerals to meet daily needs than the major minerals. (Trace minerals are also found in smaller amounts in the body.) Minerals with a daily requirement of 100 milligrams or more are considered major (or “macro”) minerals, while those with a daily requirement less than 100 milligrams are considered trace (or “micro”) minerals. The essential trace minerals are iron, iodine, zinc, copper, selenium, molybdenum, manganese, and chromium. Fluoride is another important trace mineral that is required for optimal health, but because it is not required to sustain life it is not considered an essential nutrient.

6. All of the following are general properties of trace minerals, EXCEPT:
They are found only in foods of animal origin
Many are co-factors for enzymes
Very little digestion is required
They are absorbed primarily in the small intestine
They circulate freely in the blood
The correct answer is A.

7. Trace minerals share general properties.
Less than 100 mg required daily
Circulate freely in the blood
Found in both plant and animal foods
Many serve as co-factors for enzymes
Require very little digestion
Absorbed mostly in the small intestine
Although the body doesn’t need large amounts of the trace minerals, they are crucial for health. Trace minerals often act as co-factors by binding to enzymes, enabling them to carry out their chemical reactions. Trace minerals are also incorporated into other types of proteins in addition to enzymes; iron, for example, is a component of the oxygen-carrying protein in red blood cells called hemoglobin. Trace minerals also serve other roles.
Fluoride, for example, has an important structural function in that it hardens the enamel on our teeth, reducing the incidence of dental caries.

8. Trace minerals have vital roles in the body,
Co-factors
Non-protein inorganic substances, often a mineral
Bind to enzymes, enabling them to carry out chemical reactions or other functions

9. Trace minerals are found in both animal and plant foods, but the bioavailability varies.
Bioavailability influenced by
Form of the food
Nutrition status
Age
Pregnancy
Narrow safe range of intake
Intake above the UL possible through supplements
Trace minerals are found in plant-based and animal-based foods, but their bioavailability—the extent to which a mineral can be used by the body—can be influenced by many factors, including the form of the food, our nutrition status, our age, and pregnancy status. The safe range of intake for trace minerals is also narrow compared with the major minerals, since they are required in such small amounts. It’s rare to overconsume minerals through food alone, but using supplements can result in intakes above the UL and thus potentially dangerous adverse effects. Eating a balanced and varied diet can provide enough trace minerals.

10. The majority of iodine intake in the United States comes from:
Fruits and vegetables
Iodized salt
Milk and processed grains
Nuts and vegetable oils
The correct answer is C.

11. 15% of daily salt intake in the United States comes from iodized table salt.
Iodine content of food depends on content of the environment it comes from.
U.S. salt company began to add iodine to salt in 1924.
Sources of iodine
Seafood
Milk
Processed grains
The iodine content of food depends on the iodine content of the environment it comes from, which varies from region to region. The highest naturally occurring concentrations of iodine are in foods from the sea, such as fish, shellfish, and plants (e.g., seaweed, algae), because the ocean contains considerable iodine. In part because the problem of goiter was so widespread, the U.S. salt company Morton began to add iodide to its salt in 1924, and the U.S. Food and Drug Administration recommended that the product be labeled with the following message: “This salt provides iodide, a necessary nutrient."
Although iodine is added to most table salt in the United States, only 15% of daily salt intake comes from iodized table salt. The majority of salt intake in the United States comes from processed foods, but food manufacturers often use non-iodized salt. Milk and processed grain products provide the majority of total iodine intake in the United States (about 70%). Iodine in milk originates primarily from the fortification of animal feed and the use of iodine-containing sanitizers during milk collection, while its presence in processed grain products is largely due to the use of iodine-containing food additives (dough conditioners).

12. Iodine is an essential component of thyroid hormone.
Required for normal function of thyroid gland
Thyroid-stimulating hormone (TSH)
Regulates the thyroid
Increases uptake of iodine in blood
Stimulates thyroid hormone production and release
Thyroid hormones
Regulates energy metabolism and protein synthesis
Critical role in the development of the fetal skeleton and brain
Iodine is an essential component of thyroid hormone, thus it is required for normal function of the thyroid gland. The pituitary gland in the brain secretes thyroid- stimulating hormone (TSH), which regulates the thyroid by increasing the uptake of iodine from the blood, stimulating thyroid hormone production and release. The thyroid hormones regulate energy metabolism and protein synthesis and play critical roles in the development of the fetal skeleton and brain, which is why iodine deficiency is especially problematic during pregnancy.

13. Regulation of Thyroid Hormone Production
When individuals do not get enough iodine, the thyroid gland cannot produce adequate levels of thyroid hormones. This can lead to goiter or hypothyroidism (underactive thyroid), which slows the metabolic rate.

14. Iodine deficiency impairs ability of thyroid gland to produce thyroid hormones.
Hypothyroidism
Slow metabolic rate
Goiter
Cretinism
Mental retardation, deafness, stunted growth, and other abnormalities
Mild forms of iodine deficiency in pregnancy can affect neurological development
Goiter can occur when the thyroid gland—an endocrine gland located at the front of the neck—is not able to make enough thyroid hormone to meet the body’s needs. The TSH levels rise and the thyroid gland attempts to make thyroid hormones, but it does not receive enough iodine. The thyroid gland grows and expands, trying to do its job, forming a lump in the neck that can grow as large as a grapefruit.
The milder iodine deficiencies that have developed in the United States are most common among pregnant women, as the RDA for iodine during pregnancy is 50% higher than it is for non-pregnant women. Lack of iodine can adversely affect brain development and growth of the developing fetus. If a pregnant woman is extremely deficient in iodine, then cretinism can develop in her child, characterized by mental retardation, deafness and muteness, stunted growth, delayed sexual maturation, and other abnormalities. Less severe iodine deficiencies can affect neurological development in young children, resulting in below average intelligence. Because of these problems, iodine supplements are sometimes recommended for pregnant women and women of child-bearing age (unfortunately many prenatal vitamins do not contain supplemental iodine).

16. The RDA for iodine for adults is 150 micrograms.
The RDA for iodine for men and women 19 years and older is 150 micrograms. Iodine is naturally highest in seafood, but it is found in significant amounts in milk and processed grains.

17. Excessive iodine intake can disrupt thyroid function.
UL = 1,100 mcg
Excessive intake can cause
Some of same symptoms of deficiency
Goiter
Hypothyroidism
Elevated TSH
The UL for iodine is 1,100 micrograms. Excessive intake can elevate levels of TSH, disrupting thyroid function and sometimes causing some of the same symptoms as iodine deficiency: goiter, elevated TSH levels, and hypothyroidism.

18. In contrast to heme iron, non-heme iron:
Is found only in animal foods
Makes up the majority of iron we consume
Is better absorbed by the body
Is more influenced by dietary components that inhibit absorption
Is the most prominent form of iron in the body
The correct answer is B.

19. Iron (Fe) is a crucial component of hundreds of enzymes and other proteins in the body.
Required for chemical processes including
Energy metabolism
Immune response
DNA synthesis
Important in reproduction, growth, and healing
Most abundant trace mineral in our bodies
Present in
Heme iron
Hemoglobin
Myoglobin
Non-heme iron
Iron occurs as heme iron in hemoglobin and myoglobin. Iron is also an integral component of many enzymes required for a host of crucial processes in the body, including energy metabolism, protection against antioxidants, the immune response, and DNA synthesis. Because of its role in DNA synthesis, iron is required for a wide variety of critically important functions, including reproduction, growth, and healing. Although most iron is in the heme form in the body, non-heme iron is also important because it assists enzymes in their functioning.
For example, the enzymes that bind iodine to form thyroid hormone, and metabolize beta-carotene to vitamin A, both use non-heme iron as a co-factor.

20. Heme iron is a critical part of the protein hemoglobin.
Most iron in our body occurs as heme iron. Heme iron is a critical part of the protein hemoglobin. In the body, red blood cells pick up oxygen from the lungs and release it into the tissues. Red blood cells are able to pick up and transport oxygen because they contain a protein within them called hemoglobin. Hemoglobin is made up of four units, each unit contains one heme group (an iron atom surrounded by a ring-shaped structure) and one protein chain. These heme groups contain positively charged iron atoms that can bind to oxygen molecules and transport them to various areas of the body.
The structure of hemoglobin allows it to be loaded with oxygen in the lungs, so it is sometimes referred to as an oxygen transport protein.

21. The iron-containing protein in muscle is myoglobin.
In muscles, the iron-containing oxygen storage protein is myoglobin, which is similar in structure to hemoglobin but has only one heme unit and one protein chain. Myoglobin contains less heme iron than hemoglobin.
Myoglobin transports and stores oxygen in muscle cells and helps to coordinate the supply of oxygen to the demand of working muscles.

22. Oxygen is carried by hemoglobin in blood and supplied by myoglobin in muscle.

23. Iron is better absorbed when consumed with orange juice or tomato sauce.
Yes No
Answer is A.

24. Food sources of iron include both heme and non-heme forms.
Heme in red meats, poultry, and fish
Non-heme in plant foods
Lentils, beans, dried fruits, and grain products
Absorption
Increased by vitamin C, acid, and meat
Decreased by soy protein, phytates, and polyphenols, as well as calcium intake
Food sources offer iron in both the heme and non-heme forms. Dietary heme iron (from hemoglobin and myoglobin in animals) is present in red meats, poultry, and fish. Non-heme iron is also found in meat and fish; additionally, it is the only form of iron found in plant foods, such as lentils and beans, dried fruits, and grain products—particularly those grain products that have been fortified with iron. Although non-heme iron makes up the majority of the iron that we consume, it is not as well-absorbed by the body as heme iron.
Iron balance in the body is regulated by iron absorption, storage, release, and transport. Iron stores in the body are regulated only by controlling its absorption in the small intestine, because, unlike other minerals, iron cannot be excreted in urine or bile. In healthy individuals about 10% to 15% of dietary iron is absorbed. However, when iron stores are low, iron is absorbed more efficiently, and when its stores are high, iron is absorbed less efficiently.

25. Iron Recommendations

26. Non-heme iron is strongly influenced by absorption enhancers and inhibitors.
Non-heme iron is strongly influenced by absorption enhancers and inhibitors, while the absorption of heme iron is little affected. For example, non-heme iron absorption is enhanced when consumed with vitamin C or with meat, fish, or poultry.
On the other hand, soy protein, phytates (compounds found in whole grains and legumes), and polyphenols (such as tannins in tea and red wine) have been shown to inhibit non-heme iron absorption by binding to iron in the gastrointestinal tract. Calcium is the only dietary factor that may reduce the absorption of both heme and non-heme iron. Because calcium and iron compete with each other for absorption, when large amounts of calcium (such as from calcium supplements) are consumed with iron at the same time or during the same meal, iron absorption is decreased. However, studies have found that calcium has little long-term effect on iron absorption and status.

27. As many as 30% of the world’s population may suffer from iron deficiency anemia.
Iron deficiency anemia
Caused by blood loss
Insufficient iron intake
High-risk groups
Children, pregnant, and menstruating women
Symptoms
Tired, out of breath, poor performance, and slow cognitive and social development
As many as 30% of the world’s people may suffer from iron deficiency anemia (also known as microcytic hypochromic anemia), a serious condition that develops gradually when a person’s iron intake does not meet his or her daily needs. “Anemia” refers to a shortage of hemoglobin, and “iron deficiency” refers to the cause of that shortage. When iron intake is low over time, iron stores can become depleted; if iron stores become completely depleted, blood levels of iron fall, and hemoglobin synthesis is impaired. The decrease in hemoglobin synthesis results in less hemoglobin incorporation into red blood cells, and iron deficiency anemia develops.
Iron deficiency anemia has many causes. The most common cause is blood loss. The combination of blood loss through menstruation and a limited or restricted diet that may minimize sources of heme iron can put premenopausal women at risk of iron- deficiency anemia. It is estimated that 15% of women aged 20 to 49 years may have iron-deficiency anemia. It can also result from insufficient dietary iron intake and is more common among vegans, who avoid foods of animal origin, and thus consume no heme iron through food consumption. The condition can also develop when the mineral cannot be properly absorbed because of disease or the presence of dietary components that inhibit non-heme iron absorption. Infants and young children need higher- than-normal amounts of iron because they are rapidly growing; iron needs are also increased during pregnancy. Iron lost through menstruation, frequent blood donations, or any other form of blood loss must be re-placed. Adult men and postmenopausal women are at lower risk for iron deficiency anemia, because they lose very little iron through blood loss.
The World Health Organization considers iron deficiency to be the number one nutritional disorder in the world, affecting as much as 80% of the world’s population in both developing and industrialized nations.

28. RDA for iron assumes most of iron consumption is heme iron.
RDA for men >19 years of age = 8 mg
RDA for women 19 to 50 years of age = 18 mg
RDA for vegetarians doubled (non-heme iron)
Athletes may have a 30% higher requirement.
The RDA for iron for men 19 years and older is 8 mg; for women aged 19 to 50 years, it is 18 mg. However, these recommendations assume that 75% of iron consumption is heme iron, so for vegans and vegetarians, who primarily ingest non-heme iron, intake re-commendations are approximately doubled. Athletes who train intensively on a regular basis are estimated to have a 30% higher average iron requirement because of increased iron losses. National nutrition surveys suggest that men of all racial and ethnic groups consume the recommended amounts of iron, but intakes are generally lower than recommended in women of childbearing age and young children.

29. Excess iron intake causes adverse effects in adults and can be lethal in children.
UL for men and women >19 years of age = 45 mg
Cause gastrointestinal distress
Diarrhea, constipation, nausea, vomiting
Iron toxicity causes apathy, fatigue, liver damage, and immune problems.
Iron poisoning
Unintentional death in children
Nausea, vomiting, diarrhea, rapid heartbeat, dizziness, shock, and confusion
The UL for iron for men and women 19 years and older is 45 mg, and higher intakes of iron can cause gastrointestinal distress. Individuals who take high doses of iron to prevent or treat iron deficiency anemia also sometimes suffer from side effects, including constipation, nausea, vomiting, and diarrhea, especially when the supplements are taken on an empty stomach. Because very little iron is excreted from the body, iron toxicity can occur when intake is too high, causing symptoms such as apathy, fatigue, liver damage, and immune problems.
In children, iron poisoning is a major cause of unintentional poisoning death, causing symptoms such as nausea, vomiting, diarrhea, constipation, rapid heartbeat, dizziness, shock, and confusion (which explains why you will not find iron in “gummy” multivitamin/mineral supplements; children might mistake them for candy and consume too many with potentially fatal results). Men are at a higher risk for iron toxicity than are women because men don’t experience monthly blood loss. Individuals with hereditary hemachromatosis, sometimes called iron overload disease, are also at high risk of iron toxicity because of increased absorption and high iron stores.

30. Which trace mineral is required for the function of perhaps more proteins in the body than any other mineral?
Copper
Chromium
Iron
Selenium
Zinc
The correct answer is E.

31. Dr. Prasad studied growth retardation in developing countries.
Zinc (Zn) supplementation in at-risk children may help improve immunity, growth, and development.
Dr. Prasad studied growth retardation in developing countries.
Diets that rely on bread and grains
High in phytates that bind iron and zinc
Prevent proper absorption
Growth retardation and delayed sexual maturation
In 1958, a young physician named Ananda Prasad evaluated a patient in Iran who suffered from severe iron deficiency and its associated symptoms. In addition, the severely stunted patient appeared to be about eight years old and had not gone through puberty, although his chronological and bone age indicated he was closer to 21 years old. This was not an isolated case; the same condition was so prevalent in Iran that it was considered an epidemic. Dr. Prasad studied the curious problem, administering iron to the patients with iron deficiency. However, Prasad found it difficult to assign all the health problems to iron deficiency, since growth retardation and the lack of secondary sex characteristics are not typically linked to iron deficiency.
Seeking clues to effectively treat the patients, Prasad went to Egypt to study rural farmers with similar signs of illness, taking careful inventory of their diets. Soon, Prasad began to target the mineral zinc, which, at that time, was not thought to be of importance to human health. He knew that in the developed world, zinc is found in a variety of food sources, such as fish, red meat, and dairy products. However, the diets of the individuals he studied from the developing world relied heavily on breads and grains, which contain phytates, which are substances that bind zinc and iron and prevent both minerals from being properly absorbed, accounting for both the iron deficiency and the zinc deficiency. In 1961, Dr. Prasad published an article in the American Journal of Medicine, suggesting for the first time that zinc deficiency could account for human growth retardation. By 1963, Dr. Prasad started administering zinc through clinical trials, and his participants began growing taller and developing secondary sex characteristics.

32. Zinc (Zn) is required for the function of more proteins in the body than any other mineral.
Co-factor for over 900 enzymes
Required for almost every essential process in the body
Regulation of protein synthesis
Reproduction
Cell division
Growth and development
Immune responses
Neurological functions
Zinc (Zn) is required for the function of perhaps more proteins in the body than any other mineral. Research indicates that zinc binds to about 10% (about 2,800) of all proteins in the body, including more than 900 enzymes.
Zinc functions as a co-factor for enzymes that participate in most major metabolic pathways. The binding of zinc to proteins also plays critically important structural roles by allowing proteins to achieve and maintain their appropriate shapes. The prolific presence of zinc in so many enzyme systems and regulatory proteins means that it is required for virtually every essential process in the body, including the regulation of protein synthesis, reproduction, cell division, growth and development, immune responses, and neurological functions.

33. It is estimated that about 12% of the U. S
It is estimated that about 12% of the U.S. population is at risk for zinc deficiency.
Symptoms of mild to moderate deficiency
Impaired immune function
Appetite loss and weight loss
Delayed sexual maturation
Stunted growth
Severe deficiency can result in hair loss, diarrhea, infertility in males, and impaired neurological and behavioral function
At-risk groups
Alcoholics
Vegetarians
Elderly
Alcohol decreases absorption and increases excretion.
Phytates inhibit absorption.
Although zinc deficiencies serious enough to produce readily identifiable symptoms are uncommon in the United States, it is estimated that about 12% of the population is at risk of deficiency. Some groups, including alcoholics, vegetarians, and the elderly, are particularly at risk of a zinc deficiency. Alcohol reduces zinc absorption and increases zinc excretion in the urine, while phytates in whole grains and legumes, which are dietary staples among vegetarians, inhibit the mineral’s absorption. Zinc status in the elderly may be compromised because of reduced food intake and impaired absorption resulting from low gastric acid production.
Mild to moderate zinc deficiency can cause impaired immune function, appetite loss and weight loss, delayed sexual maturation, and slowed growth. Severe zinc deficiency results in hair loss, diarrhea, infertility in men, and impaired neurological and behavioral functions. Symptoms of zinc deficiency can mimic symptoms of other nutrient deficiencies and can occur alongside other deficiencies in part because zinc plays an important role in the proper functioning of many other nutrients.

34. The body cannot store zinc, so regular daily intake is required.
RDA for males >19 years of age = 11 mg
RDA for females >19 years of age = 8 mg
Vegetarians’ needs are doubled.
UL = 40 mg
Excessive intake can lead to nausea, vomiting, diarrhea, copper deficiency, reduced immune function, and altered iron function
The recommended intake of zinc is 11 mg for men 19 years and older and 8 mg for women in the same age group. Since the body cannot store zinc, a regular daily intake is required to maintain adequate zinc status, although absorption does increase in the small intestine when intake is low. Because vegetarians absorb less zinc than nonvegetarians do, the Dietary Reference Intakes recommend that vegetarians and vegans consume twice as much zinc as nonvegetarians.
The UL for zinc intake for men and women 19 years and older is 40 mg. Short-term symptoms of excessive zinc intake include nausea, vomiting, abdominal cramps, and diarrhea. Chronic, longer-term effects may include copper deficiency (excessive zinc reduces the absorption of copper), altered iron function, reduced immune function, and lowered levels of high-density lipoproteins.

35. Zinc is found in many foods but is concentrated in meats, poultry, and some seafood.
Zinc is found in many foods but is most concentrated in meats, poultry, and certain types of seafood, such as oysters, which contain more zinc per serving than any other food. Fortified cereals, beans, and nuts also provide zinc, as do certain brands of cold lozenges and some over-the-counter drugs sold as cold remedies.

36. Copper (Cu) is essential for a variety of physiological processes in the body.
Functions
Co-factor in oxygen-dependent enzymes
Energy metabolism
Formation of connective tissues
Regulation of iron storage and transport
Antioxidant functions
May slow progression of age-related macular degeneration
Copper functions as a co-factor in oxygen-dependent enzymes in the body. Though there are only about a dozen copper-containing human enzymes, they participate in a variety of critical physiological processes, including but not limited to energy metabolism, formation of connective tissue, regulation of iron storage and transport, and antioxidant functions. Copper may play a role in slowing the progression of age-related macular degeneration, which is responsible for causing severe vision loss in the elderly.

37. Copper deficiency is rare in the United States.
Mostly secondary to other factors
Malabsorption from other conditions
Gastric bypass surgery
Excessive zinc intake
Symptoms
Anemia
Impaired immune response
Osteoporosis
Deficiencies of copper from low dietary intakes are rare in the United States as most of the population meets or exceeds the RDA for copper. However, deficiencies that are secondary to other factors are more common. Copper deficiencies are somewhat common in people who have gastric bypass surgery to treat obesity, as well as in those with other conditions that cause nutrient malabsorption. Excessive zinc intake decreases copper absorption and is another cause of copper deficiency. Anemia may result from copper deficiency as copper-containing enzymes are required to release iron from stores and for its incorporation into its heme form. Symptoms of copper deficiency also include impaired immune response and osteoporosis.

38. Copper is absorbed more efficiently than other trace minerals.
RDA = 900 mcg
The RDA for copper is 900 micrograms per day in adults. Approximately 55% to 75% of dietary copper is absorbed, which is much more efficient than other trace minerals. Although copper is found in a wide variety of foods, it is highest in organ meats, shellfish, nuts, seeds, mushrooms, chocolate, and legumes.

39. About two dozen selenium-containing human proteins have been identified.
Functions
Co-factor of several antioxidant enzymes
Activation of thyroid hormone
Essential for normal growth, development, and metabolism
Selenium functions as a co-factor for several antioxidant enzymes and with other selenium-dependent enzymes in the activation of thyroid hormone, making it essential for normal growth, development, and metabolism.

40. Selenium deficiency, when combined with additional stresses, has adverse effects.
Deficiency increases risk of vitamin E deficiency
Low selenium status
Increases risk for a particular form of heart disease
May increase risk of some cancers
Decreases immune function
A selenium deficiency by itself seldom causes obvious symptoms or illness. However, additional stresses, such as viral infections, chemical exposure, or low intakes of other antioxidant nutrients, together with low selenium intake can cause clinical illness. For example, a selenium deficiency increases the likelihood of developing a vitamin E deficiency (low intake of this vitamin). This occurs because selenium functions as a co-factor for an important antioxidant enzyme system and a deficiency of selenium increases oxidative stress and places a greater demand on the antioxidant function of vitamin E. Low selenium status increases the risk of a particular form of heart disease and may increase the risk of some cancers. Inadequate selenium may also decrease immune function.

41. The most common sources of selenium are meats and fortified cereals.
RDA = 55 mcg
UL = 400 mcg
Hair and nail brittleness and loss
Single high dose may be fatal
Food sources
Meats and cereals
Plant food sources vary due to soil concentrations
Brazil nuts
The RDA for selenium is 55 micrograms per day for adults. The highest concentrations of selenium are present in organ meats and seafood. The most common sources in the diet are meat and cereals. The selenium content of meats is fairly consistent, but the selenium content of plant foods varies widely depending on the content of the mineral in the soil where the plant was grown. Dietary selenium is generally well-absorbed, and unlike most other minerals, its absorption is not regulated in relation to nutritional status.
The UL for selenium is 400 micrograms per day in adults. Although a single high dose of selenium may be fatal, selenium toxicity generally occurs with long-term exposure to moderately high levels of intake either through supplementation or, in rare instances, through frequent consumption of selenium-rich foods. For example, a single one-ounce serving of about six Brazil nuts contains 544 micrograms of selenium, which is about 25% above the UL. The most common toxicity symptoms are hair and nail loss, and brittleness.

42. Other trace minerals have important roles in health and disease prevention.
Chromium (Cr)
Enhances the action of insulin
Fluoride
Hardens the enamel of our teeth
Helps protect against dental caries
Long-term excessive intake may have adverse effects on bone
Manganese
Co-factor for enzymes in antioxidant function, energy metabolism, bone development, and neurotransmitter production
Molybdenum
Co-factor for four enzymes in metabolism
Chromium is a popular dietary supplement, yet despite the hype, its proposed benefits have not been supported by the results of intervention trials. There is essentially no credible evidence that it promotes weight loss, or that it improves muscle mass with resistance training. Perhaps even more surprising, recent studies have failed to conclusively demonstrate that chromium can enhance the ability of insulin to control blood glucose, and no progress has been made in identifying the means by which chromium might exert its biological affects.
Fluoride has a well-established role in the prevention of dental caries through the hardening and maintenance of tooth enamel. Fluoride is also important in stabilizing the structure of bone. As fluoride is not required for growth, for reproduction, or to sustain life, it is not by definition considered an essential nutrient. Fluoride may cause health issues if drinking water exceeds the standards set by the EPA. Tooth and skeletal fluorosis is characterized initially by small opaque flecks on the teeth and then by stains or pits in the teeth with longer-term exposure. The EPA warns that excessive intake over a lifetime may have adverse effects on bone, among them an increased likelihood of fractures because bones become brittle as they become excessively dense.
Manganese functions as a co-factor for enzymes involved in antioxidant functions and is involved in the metabolism of carbohydrates, cholesterol, and amino acids. The role of manganese in amino acid metabolism makes it important for the synthesis of proteins needed for bone growth and maintenance, as well as for wound healing.
Molybdenum is a co-factor for only four enzymes, and the function of one of these enzymes is not well understood. The average intake of the United States population is usually well above the RDA;
deficiencies are unknown in healthy individuals and the risk of toxicity in humans is very low.

43. Which of the following is NOT an ultratrace mineral?
Boron
Manganese
Nickel
Silicon
Vanadium
The correct answer is B.

44. Ultratrace minerals have a potential intake requirement of less than 1 mcg/day.
Food only safe source of intake
Specific biological or physiological functions not yet identified
Not currently classified as essential
Animal data suggest these may be important
Arsenic (As)
Boron (B)
Nickel (N)
Silicon (Si)
Vanadium (V)

45. Summary of the Trace Minerals

46. Summary of the Trace Minerals (Cont’d)

47. Summary
Trace minerals are essential nutrients required in very small amounts in human nutrition and include chromium, copper, fluoride, iodine, iron, manganese, molybdenum, selenium, and zinc.
Trace minerals have vital roles in the body, such as participating as co-factors in numerous chemical reactions.
Found in both plant and animal foods, the actual bioavailability of trace minerals is influenced by many factors.
Trace mineral deficiencies can have varied, yet serious, consequences particularly of concern in pregnant woman and growing children.

48. Summary (Cont’d)
Trace minerals are found across all food groups; thus, sufficient intake can generally be achieved by consuming a varied and balanced diet.
Ultratrace minerals are not currently classified as essential nutrients but may have important values in the body. They are arsenic, boron, nickel, silicon, and vanadium.