Chapter
13
Trace Minerals
What Are Trace Elements? • Needed in small amounts in the diet • < 100 mg/day
• Found in small amounts in the body
What Are Trace Elements? • Why are trace elements important? • Crucial to many body functions, including metabolic pathways
• Other characteristics of trace elements
Iron: Functions
Iron • Enzymes • Energy metabolism • Immune function
Regulation of Iron Absorption
Regulation of Iron Absorption • Process of iron absorption • Effect of body’s iron status on iron absorption • Effect of GI function on iron absorption • Effect of the amount and form of iron in food • Dietary factors that enhance iron absorption • Dietary factors that inhibit iron absorption
Regulation of Iron Absorption • Iron absorption and vegetarianism • Iron transport and storage • Iron turnover and loss
Iron • Dietary recommendations • Food sources • Red meats, liver, seafood
• Deficiency and measurement of iron status • Progression of deficiency
• Toxicity • Poisoning in children • Hemochromatosis © Photodisc
Functions of Zinc
Functions of Zinc • Regulation of zinc in the body • Zinc absorption • Dietary factors that inhibit zinc absorption • Zinc transport and distribution • Zinc homeostasis and excretion
Zinc • Dietary recommendations • Food sources • Red meats, seafood
• Deficiency • Poor growth, delayed development
• Toxicity • Can cause copper deficiency
Selenium • Functions • Part of antioxidant enzyme • Thyroid metabolism, immune function
• Regulation of selenium
Selenium • Dietary recommendations • Food sources • Organ meats, seafood, and meats
• Deficiency • Increases susceptibility to some infections
• Toxicity • Brittle hair and nails
Iodine • Functions • Thyroid hormone production
• Iodine absorption and metabolism
Iodine • Dietary recommendations • Food sources • Iodized salt, fish, seafood, and dairy products
• Deficiency • Goiter: enlarged thyroid gland • Cretinism: mental retardation • Occurs in fetus when pregnant woman is deficient
• Toxicity
Copper • Functions • Melanin, collagen, elastin production • Immune function • Antioxidant enzyme systems
• Absorption, use, and metabolism • Dietary recommendations • Food sources • Organ meats, shellfish, nuts, legumes
• Deficiency • Toxicity
Manganese • Functions • Cartilage production • Antioxidant enzyme systems
• Absorption, use, and homeostasis • Dietary recommendations • Food sources • Tea, nuts, cereals
• Deficiency • Toxicity
Fluoride • Functions • Bone and tooth structure
• Absorption and excretion • Dietary recommendations • Food sources • Fluoridated water
• Deficiency, toxicity, and pharmacological applications
Chromium • Functions • Glucose metabolism
• Absorption, transport, and excretion
Chromium • Dietary recommendations • Food sources • Mushrooms, dark chocolate, nuts, whole grains
• Deficiency • Toxicity
Molybdenum • • • • •
Absorption, use, and metabolism Dietary recommendations Food sources Deficiency Toxicity
Other Trace Elements and Ultratrace Elements • • • • •
Arsenic Boron Nickel Silicon Vanadium
The Impact of Fluoride on Health â&#x20AC;˘ The Academy of Nutrition and Dietetics reaffirms that fluoride is an important element for all mineralized tissues in the body. â&#x20AC;˘ Appropriate fluoride exposure and usage is beneficial to bone and tooth integrity and, as such, has an important, positive impact on health throughout life.
Factors Affecting Bioavailability of Minerals
Effects of Body’s Iron Status on Iron Absorption • Depending on the size of the body's iron stores, absorption of dietary iron (i.e., iron bioavailability) can vary from less than 1 percent to greater than 50 percent. The GI tract increases iron absorption when the body's iron stores are low and decreases absorption when stores are sufficient. • Among adults, men absorb approximately 6 percent of dietary iron and nonpregnant women of childbearing age absorb approximately 13 percent. The women's higher absorption rate primarily reflects their lower iron intake, and higher iron losses as a result of menstruation. Iron absorption also is high among iron-deficient persons.
Food Sources of Iron
Grandmaâ&#x20AC;&#x2122;s Skillet â&#x20AC;˘ Iron deficiency is the most common form of malnutrition in the United States. However, this is a relatively recent phenomenon. Americans used to cook using cast-iron pots and pans, but now use stainless steel, aluminum, and enamelware. â&#x20AC;˘ A study showed that using these iron pots and utensils to cook acidic foods like spaghetti sauce and apple butter increased the iron content of such foods by a factor of 30- to 100-fold.
Oceans Can Get Anemia, Too • Stretching from South America to New Zealand, a large region of the South Pacific Ocean suffers from an iron deficiency. • Phytoplankton and plant life are not growing properly in this area. • Researchers have identified iron deficiency as the reason.
Iron Poisoning in Children • Accidental iron overdose is a leading cause of poisoning deaths in children younger than 6 years old in the United States. • The iron products involved range from nonprescription daily multivitamin/mineral supplements for children to high-potency prescription iron supplements for pregnant women. • Even a few pills can cause the death of a small child. Symptoms of iron intoxication include nausea, vomiting, diarrhea, rapid heartbeat, dizziness, and confusion. Death can occur within hours of ingestion. If iron poisoning is suspected, the child should receive immediate emergency medical care.
Hereditary Hemochromatosis â&#x20AC;˘ Hereditary hemochromatosis, a form of chronic iron overload, was once thought to be rare but now is known to be quite common. A genetic defect causes excessive iron absorption. â&#x20AC;˘ Over the years, iron can build up in many parts of the body, leading to severe organ damage and even death. Diabetes, heart disease, cirrhosis, liver cancer, and arthritis can all be consequences of hemochromatosis.