CHAPTER 15

TRACE MINERALS

LEARNING OUTCOMES

• Describe the important food sources, major functions, deficiency and toxicities of each trace mineral discussed in class• Understand trace mineral absorption,

transportation, storage and excretion.

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OVERVIEW OF TRACE MINERALS

• Inorganic substances needed by the body in small quantities• Includes iron, zinc, copper, maganese, iodine,

selenium, chromium, fluoride, and molybdenum• Typically difficult to measure in the body and in

food

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IRON

• Foods• Heme iron: iron part of hemoglobin and

myoglobin in animal flesh• Nonheme iron: vegetables, grains, and

supplements

• Needs• RDA 18 mg/day adult women, 8 mg/day adult men• After menopause drops to 8 mg/day• Most common trace mineral deficiency worldwide

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IRON

• Absorption, Transportation and Excretion• Ferritin: iron binding protein in small intestine• Storage form of iron, made in response to iron stores• Also acts as “mucosal block”

• Transferrin: protein that binds iron and transports it through body (needs copper)

• Absorption and storage is tightly regulated in the body because the body has limited ability to excrete absorbed iron

• Most iron is recycled, only 10% is excreted

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Mucosal “block”

Muscle (Myogl)

Bone marrow

RBC (Hgb)

Liver

Non heme must be in Fe2+ form to be absorbed

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IRON

• Functions • Component of

proteins• Hemoglobin-protein in

red blood cells that carries oxygen in body

• Myoglobin- protein in muscle that carries oxygen to muscles and heart

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IRON

• Functions • Component of

enzymes or act as coenzyme

• Needed for energy metabolism

• Needed for drug and alcohol metabolism in the liver

• Needed for neurotransmitter synthesis

• Needed for immune system

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IRON

Deficiency• Iron deficiency anemia• At risk: premature infants, children, females of child bearing

age, vegetarians

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IRON DEFICIENCY

• Pale skin, fatigue and weakness. • In severe cases, trouble breathing• Pica for ice is a very specific symptom• Lightheadedness

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IRON

• UL• 45 mg/day• Nausea, vomiting, diarrhea, constipation,

interfere with absorption of other minerals• Who? • Supplements (especially kids)• Hemochromatosis- genetic disorder that can cause

liver disease and heart failure• Frequent blood transfusions

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CASE STUDY

Betsy just got diagnosed with iron deficiency anemia. What would be a good breakfast?•Iron fortified cereal with milk and coffee•Spinach and cheese omelet•Steak and eggs•Ham, egg, and cheese on whole grain bread with OJ

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ZINC

• Foods• Protein rich meat and

seafood, whole grains• Needs• RDA 8-11 mg, most in

US get adequate zinc• Absorption,

Transportation and Excretion• Has a mucosal block

similar to iron (metallothionein)

• Not stored, but is recycled

• Can be excreted in feces, so less toxic than iron

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ZN ABSORPTION

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ZINC

• Function• At least 300 different enzymes require zinc• DNA synthesis, immune function, growth and

development, home synthesis, antioxidant

• Deficiency• Overt deficiency common in poverty• Low appetite, impaired growth, decreased taste, immune

dysfunction

• North America-marginal deficiencies if absorptive diseases, dialysis, vegetarians

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ZINC

•UL• 40 mg/day-usually people who take

supplements• Low appetite, nausea, vomiting, GI upset

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COPPER

• Foods• Liver, shellfish, nuts, seeds, mushrooms, soy and

dark chocolate• Needs• RDA 900 micrograms daily• Deficiency rare

• Absorption, Transportation and Excretion• Little is stored, excreted in feces• Binds to metallothione in intestine • Copper balance controlled by copper absorption

and influenced by iron and zinc status

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COPPER

• Function• Iron metabolism• In family of enzymes

that act as antioxidants

• Deficiency rare• Menkes disease

• UL• Toxicity is also rare• Wilson’s disease

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IS CHOCOLATE GOOD FOR YOU?

• One study reported that men who ate the most chocolate had a 47 percent lower mortality rate over 15 years than a similar group that consumed little chocolate. • Another study that showed a small amount of

chocolate slowed platelet clumping. • A new chocolate called CocoaVia got a lift from

the Journal of the American Dietetic Association, which reported that two (small) bars a day lowered LDL cholesterol in a high-cholesterol subject group by 6.7 percent

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MATCH THE DEFICIENCY WITH THE ANEMIA

• Vitamin E• Folate• Vitamin B12• Iron• Copper

• Megaloblastic• Microcytic• Hemolytic

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*** See page 548 in book for summary

MANGANESE

• Foods• Whole-grain cereals, nuts, legumes and tea

• Needs• AI 1.8-2.3 mg/daily• Deficiency rare

• Absorbed in small intestine, transported with protein carriers, excreted in bile• Only ~10% is absorbed, unless need is

high• Absorbed better if iron status is good

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MANGANESE

• Function• Shares functional similarities with Zinc and

Copper (cofactor for enzymes, energy metabolism)

• Deficiency• Rare

• UL• 11 mg/day• Inhalation of car emissions• Causes nerve damage

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IODINE

• Foods• Saltwater seafood, seaweed, iodized salt,

molasses and dairy products

• Needs• RDA is 150 micrograms daily• ½ teaspoon of iodized salt meets RDA requirement

• Absorbed efficiently and stored in thyroid gland, excreted in urine

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IODINE

• Function• Component of

thyroid hormone so needed for normal metabolism

• Deficiency• Goiter (enlarged

thyroid) and cretinism (poor growth)

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IODINE

•UL• 110 micrograms/day• Enlarged thyroid gland, increased risk of thyroid cancer• Japan- high intake of seaweed• Chile- high levels in soil

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SELENIUM• Foods• Seafood, meats, cereal grains and nuts• Soil dependent

• Needs• RDA 55 micrograms adults• Intake typically above the RDA

• Easily absorbed, excess is excreted in urine

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SELENIUM

• Function• Anti-oxidant defense network (similar to vitamin E,

protects cell membranes from oxidation)• Synthesis of thyroid hormone• May decrease risk of cancer (especially prostrate

and lung)• Deficiency• No specific disease but deficiency can cause Keshan

disease• UL• 400 micrograms daily• Nausea, diarrhea, fatigue, hair loss, change in nails,

and skin rashes

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SELENIUM AND CANCER

• 1) Epidemiology studies show that where selenium levels in the soil are high, death rates from cancer are significantly lower.

• 2) Clinical trial studies• 32,000 men• Researchers gave the men either selenium, vitamin E,

or a combination of selenium and vitamin E to learn whether either would lower the risk of prostate cancer.

• This study was suspended early because analysis found no benefit to taking selenium for an average of more than 5 years.

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CHROMIUM

• Foods• Nutrient databases inadequate• In many foods including broccoli, processed

meats, liver, eggs, whole grain products

• Needs• AI 25-35 micrograms• Uncommon deficiency and no UL

• Functions• May improve insulin function and help normalize

blood sugar, although supplements have not been shown to be beneficial

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FLUORIDE

• Foods• Fluoridated water, tea, seafood and seaweed• Non food sources are toothpaste and mouthwash

• Needs• AI 3-4 mg/daily

• Easily absorbed and stored in teeth and bones• Function• Promotes bone and dental health

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FLUORIDE

• Deficiency• Associated with an

increase in dental caries

• UL• .1 mg/kg body

weight daily up to 8 years old• Most risk is 8 yo or

younger

• Mottling or fluorosis with chronic intake

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MYTHS

• I drink bottled water, am I missing out on the benefits of Fluoride?• Do I need to drink fluoridated water if I brush my

teeth?• What are other health effects of too much

fluoride?

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ULTRA TRACE MINERALS

Needed in very small amounts but essential for many enzymes

•Molybdenum•Boron•Nickel•Silicon•Arsenic•Vanadium

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