Chapter 13Chapter 13

Trace Minerals

Characteristics of this Group Characteristics of this Group of Nutrientsof Nutrients

A. Each has range of safe & adequate intake

B. Required in very small quantities which makes measuring presence in food & body difficult

C. Body maintains balance mainly by absorption. Does not excrete trace minerals well

D. Variable bioavailability

E. Deficiency may be caused by geographic location in addition to poor diet

I. Iron (Fe)I. Iron (Fe)

A. In the Body1. Exists in two ionic states

a. Ferrous reduced form, has 2 positive charges (Fe+2)

b. Ferric oxidized form, has 3 positive charges (Fe+3)

c. Forms important in oxidation-reduction reactions (TCA & ETC)

Fe in the Body (cont)Fe in the Body (cont)

2. Functionsa. Oxidation-reduction reactions of energy

metabolism

b. Structural/functional component of hemoglobin (blood) and

myoglobin (muscle)

1. carries oxygen

B. Iron Absorption and MetabolismB. Iron Absorption and Metabolism

1. Heme and Nonheme Iron

a. Heme iron meat, fish and poultry and is better absorbed (23%) (hemoglobin)

b. Nonheme iron plant foods as well as animal foods and is absorbed poorly

2. Absorption-enhancing factorsa. MFP factor nonheme iron

1. Consume meat source with nonheme Fe

b. Ascorbic Acid (vit. C) nonheme iron, at same meal

Heme and Non-heme Iron in FoodsHeme and Non-heme Iron in Foods

Heme and Non-heme Iron in FoodsHeme and Non-heme Iron in Foods

Iron Absorption and Metabolism (cont)Iron Absorption and Metabolism (cont)

3. Absorption inhibitorsa. phytates and fibers

b. calcium and phosphorus

c. EDTA in food additives

d. tannic acid (tea)

e. polyphenols (tea & coffee)

Iron Absorption and Metabolism (cont)Iron Absorption and Metabolism (cont)

4. Mucosal Transferrin intestinal cell protein which holds absorbed Fe

5. Blood Transferrin transport protein which carries Fe in blood

a. storage in bone marrow, spleen, and liver

b. ferritin and hemosiderin = storage proteins

c. iron recycling very efficient

1. lose little iron/day - blood losses

2. recycle iron back to bone marrow

Iron Absorption and Metabolism (cont)Iron Absorption and Metabolism (cont)

6. Fe balance controlled at point of absorption

a. Intestinal cell (mucosal ferritin)

7. Average absorption of Fe is ~ 10% on mixed diet

Iron Routes in the BodyIron Routes in the Body

C. Iron DeficiencyC. Iron Deficiency

1. Iron deficiency- initial stages ferritin levels decrease, transferrin increases

2. Iron deficiency w/o anemiaa. ‘Tired tissues’

1. enzymes don’t perform efficiently

3. Iron deficiency w/ anemiaa. Severe depletion of Fe stores

b. Low hemoglobin concentrations

c. Microcytic, hypochromic anemia

Iron Deficiency AnemiaIron Deficiency Anemia

Iron Deficiency (cont)Iron Deficiency (cont)

4. Prevalence of iron deficiency

a. Most common nutrient deficiency in U.S.

b. Young children & women susceptible

5. Iron deficiency and behaviora. Decreased physical work

b. Unmotivated and apathetic

c. Restlessness

d. Poor cold tolerance

e. Pale appearance, headache fatigue w/anemiaf. Pica

D. Iron Toxicity

1. Iron overload a. Genetic problem - more common in men

1. Intestine over-absorbs iron

2. Effects: tissue damage due to increased Fe

a. Hemochromatosis

1. Fe in tissues damage

b. Hemosiderosis

1. Fe in liver damage

Iron Toxicity (cont)Iron Toxicity (cont)

3. heart disease

4. Arthritis

5. increased infections due to more Fe available to microorganisms

b. Overuse of vitamin C and Fe supplements

2. Iron poisoning

a. Massive amounts can cause death

b. One of the leading causes of death and poisoning in children

E. Iron Recommendations and IntakesE. Iron Recommendations and Intakes

1. RDA men = 10 mg/day

2. RDA women (child-bearing age) = 15 mg/day

Why is the requirement higher for women?

3. Diet overalla. Only contains about 6-7 mg Fe/1000 kcal

1. Fe not much of a problem for men

2. Real problem for women

Iron Recommendations and Intakes (cont)Iron Recommendations and Intakes (cont)

4. Food sourcesa. Meat (liver is best), poultry & fish 1/3 needs

b. Milk, cheese (low absorption) & eggs 1/4 needs

c. Enriched grains 1/4 needs

d. Legumes, dark leafy vegetables, grains (nonheme iron)

1. low absorption due to other components (phytates in grains, oxalic acid in vegetables)

Iron in FoodsIron in Foods

Iron Recommendations and Intakes (cont)Iron Recommendations and Intakes (cont)

5. Contamination and Supplementationa. Contamination Iron

1. cookware

a. Iron salts enter into food

b. Cooking in an iron pot can increase the iron in the food as much as 500%

b. Supplements

1. pregnant women

2. ferrous sulfate

Iron ContaminationIron Contamination

III. Zinc (Zn)A. Roles in the Body

1. Important in many enzyme systemsa. genetic materialsb. digestive enzymesc. heme synthesisd. essential fatty acid metabolisme. CHO metabolismf. protein synthesisg. metabolism of alcoholh. free radical disposali. release vitamin A stores

Zinc (cont)B. Zn Absorption and Metabolism

1. metallothionein a. Zn binding proteinb. regulates Zn absorption

2. Zn transporta. Albuminb. Transferrin

3. Zn interaction w/ copper & irona. high zinc causes low copper absorption

1. Copper binds to metallothionein (trapped)

b. binds w/ transferrin --> decreases iron absorptionc. high Fe intakes cause low Zn absorption

Zinc in the BodyZinc in the Body

Zinc (cont)

C. Zinc Deficiency1. low intake2. high phytate (grains and cereals or

unleavened bread)3. symptoms

1. growth retardation2. arrested sexual maturation3. decreased taste and digestive function4. impaired immune response5. central nervous system and brain affected

Zinc deficiency (cont) Symptoms (cont)Zinc deficiency (cont) Symptoms (cont)

6. slowed wound healing7. affects vitamin A function8. disturbs thyroid function and

metabolic rate

4. Vulnerable groups1. pregnant women2. young children3. elderly4. poor

Zinc (cont)

D. Zinc Toxicity1. Related to overuse of supplements2. Small doses over time

a. can affect the heart (interfere with copper)

3. Larger doses

a. diarrhea, vomiting, fever, anemia, exhaustion

4. Zinc Recommendations and Intakesa. RDA men = 15 mg/dayb. RDA women 12 mg/day

Zinc (cont)Zinc (cont)

E. Food sources1. meats2. shellfish3. liver

Zinc in FoodsZinc in Foods

IV. IodideA. Function

1. Part of thyroid hormonesa. Thyroid hormones control BMR

B. Deficiency1. Goiter

a. low Iodide intake (simple goiter)

b. high goitrogen intake (toxic goiter)1. thyroid antagonist

2. Goitrogens are found in cabbage, cauliflower, broccoli, brussel sprouts (few others)

GoiterGoiter

Iodine (cont) goiter (cont)Iodine (cont) goiter (cont)

c. causes sluggishness and weight gain

2. cretinisma. Iodine deficiency in uterob. Severe mental retardation

C. Toxicity

1. 2000 µg/day toxic

Iodine (cont)

C. Iodine Recommendations and Intakes1. RDA men and women 150 µg/day2. U.S. intake 200-500 µg/day3. 2000 µg/day toxic4. Sources

a. coastal areas --> seafoodb. variable in soilc. iodized saltd. food processing

V. FluorideA. Roles in body1. make bones and teeth resistant to decay

B. Fluoridation and dental caries1. decreased tooth decay where water fluoridatedC. Fluoridation and Osteoporosis1. unclear whether beneficial or detrimental

Fluoride (cont)Fluoride (cont)

D. Fluoride Toxicity1. moderate intakes

a. mottled teeth

2. high intake (water)a. nauseab. diarrheac. chest paind. itching e. vomiting

Population (%) Using Fluoridated WaterPopulation (%) Using Fluoridated Water

VI. Chromium

A. Roles in the Body1. glucose tolerance factor

a. potentiates insulin actionb. increases glucose uptake by cells

B. Chromium Recommendations 1. estimated safe and adequate intake

a. 50-200 µg/day

Chromium (cont)Chromium (cont)

2. sources a. liverb. brewer's yeastc. nutsd. cheeses e. whole grains(unrefined foods)

Chromium (cont)Chromium (cont)

C. Chromium Supplements1. used to treat glucose abnormalities2. chromium picolinate

a. hypothesized 1. reduces body fat 2. increases lean body weight

b. controlled experiments1. no effect over placebo2. one study increased fat gain.

VII. SeleniumA. Roles in the Body

1. antioxidanta. Enzyme glutathione reductase 1. Prevents free-radical

formation

2. Functions with vitamin E

2. Thyroid glanda. Conversion of T4 to T3 (active hormone)

B. Selenium intake1. Soil concentration varies in the world 2. Intake dependent on soil

Selenium (cont)C. Deficiency

1. Relationship between Se intake and heart disease 2. Relationship between Se intake and certain cancers (skin)

D. Selenium toxicity1. RDA is 70 ug/day for men, 55 for

women

2. 1 mg/day is toxica. vomiting, diarrhea, loss of hair and nails, skin

lesions