Lec. 6

Introduction Minerals constitute about 4% of body weight. The

major mineral content of the skeleton consists of calcium and phosphorus in a ratio of approximately 2:1. Any change of one may be reflected in changes of the other.

Minerals are present in the body in a diverse array of organic compounds such as phosphoproteins, phospholipids, hemoglobin, and thyroxine; in inorganic compounds such as sodium chloride, potassium chloride, calcium, and phosphate; and as free ions.

Different body tissues contain different quantities of different elements. For example, bone has a high content of calcium, phosphorus, and magnesium; soft tissue has a higher quantity of potassium.

Minerals function as constituents of enzymes, hormones, and vitamins. They are involved in regulating cell membrane permeability, osmotic pressure, and acid-base and water balance.

Unlike vitamins, minerals exist in plants in varying amounts, according to the composition of the soil in which the plant is grown.

Mineral intake varies considerably from region to region, although the use of foods delivered from diverse geographic locations tends to minimize intake variations.

Mineral deficiency is often difficult to evaluate.

Trace ElementsTrace elements, which are present in minute quantities

in plant and animal tissue, are considered essential for

numerous physiologic processes.

"Ultratrace mineralsUltratrace minerals" have been defined as those

elements with an estimated dietary requirement of

usually less than 1 mcg/g.

1. Chromium Description

About 5 mg of chromium is present in the normal

adult, and levels decline with age.

Higher concentrations occur in the hair, spleen,

kidney, and testes, and lesser concentrations are

present in the heart, pancreas, lungs, and brain.

Chromium functions to maintain normal glucose

use.

Fatty acid stimulation and cholesterol synthesis are attributed to chromium.

Significant amounts of chromium are present in liver, fish, whole grains, and milk.

Indications Deficiency of trivalent chromium, the chemical form

present in diets, is manifested by: 1. Glucose intolerance, 2. Elevated circulating insulin, 3. Glycosuria, 4. Fasting hyperglycemia, 5. Elevated serum cholesterol and triglycerides,6. Neuropathy, and encephalopathy.

7. Impaired glucose tolerance may be a

manifestation of chromium deficiency,

especially in older persons and protein-calorie

malnourished infants.

8. Low chromium concentrations have been

associated with juvenile diabetes and coronary

artery disease.

Dose/RDA

The estimated safe and adequate dietary intake for

adults has been set at 50-200 mcg per day.

Chromium has a relatively high margin of safety.

Chromium is available in 1-mg tablets.

Adverse Effects/Drug Interactions

The oral administration of trivalent chromium has

not been reported to be toxic.

2. IodineDescription

The thyroid gland contains about one-third of the iodine in the body, stored in the form of a complex glycoprotein, thyroglobulin.

The only known function of thyroglobulin is to provide thyroxine and triiodothyronine. These hormones regulate the metabolic rate of cells and therefore influence physical and mental growth, nervous and muscle tissue function, circulatory activity, and the use of nutrients.

Iodine is required to synthesize thyroxine and

triiodothyronine and is an essential micronutrient.

Although in high concentrations iodine inhibits the

release of these hormones, in its absence thyroid

hypertrophy occurs, resulting in classic goiter.

The consumption of foods from diverse sources and the

addition of iodide to table salt have essentially eliminated

goiter.

The primary dietary source of iodine is iodized salt, which contains 1 part of sodium or potassium iodide per 10,000 parts (0.01%) of salt.

A dose of about 95 mcg of iodine can be obtained from about one-fourth of a teaspoon of salt (1.25 g).

Additional dietary sources of iodine include saltwater fish and shellfish. Seacoast soils used for raising vegetables produce vegetables with higher iodide content because plants extract iodine from the soil.

Dose/RDAThe RDA value of iodine is 0.15 mg for adults.

Potassium iodide is available as a tablet and solution and is included in various combination products.

Adverse Effects/Drug InteractionsSymptoms of chronic iodide intoxication (iodism)

include an unpleasant taste and burning in the mouth or throat along with soreness of the teeth or gums. Increased salivation, sneezing, irritation of the eyes, and swelling of the eyelids commonly occur.

3. Iron Description

Iron plays an important role in oxygen and electron transport. In the body, it is either functional or stored.

Functional iron is found in hemoglobin, myoglobin, heme-containing enzymes, and transferrin, the transport form of iron. The hemoglobin of red blood cells represents the major body store of iron, containing 60-70% of total body iron. The rest is stored primarily in the form of ferritin and hemosiderin; storage sites are the intestinal mucosa, liver, spleen, and bone marrow.

Normally, adult men have iron stores of about 50 mg/kg

of body weight; women have about 35 mg/kg of body

weight. The normal hemoglobin level in adult men is

about 14-17 g/100 mL of blood; in adult women it is 12-

14 g/100 mL of blood.

Dietary iron is available in two forms. Heme iron is

found in meats and is reasonably well absorbed.

Nonheme iron constitutes most of the dietary iron and is

poorly absorbed.

About half of the iron in meats is heme iron, which is about 25% absorbed. The amount of absorbable nonheme iron contributed by vegetables and grains in the diet varies greatly.

Iron is lost from the body (1) by the sloughing of skin cells and GI mucosal cells; (2) by hemorrhagic loss; (3) by menstruation; and (4) by excretion of urine, sweat, and feces.

Indications

Symptoms of iron deficiency are, easy fatigability, weakness, and lassitude. Other symptoms of anemia include pallor, split or "spoon-shaped" nails, sore tongue, angular stomatitis, dyspnea on exertion, palpitation, and a feeling of exhaustion. Coldness and numbness of extremities may also be reported. Small red blood cells and low hemoglobin concentrations characterize iron deficiency.

Iron deficiency results from inadequate diet, malabsorption, pregnancy and lactation, or blood loss.

The four life periods during which iron deficiency is most common are:

1) From 6 months to 4 years of age, because of the low iron content in cow's milk;

2) During early adolescence, when rapid growth entails an expanding red cell mass and the need for iron in myoglobin;

3) During the female reproductive years, owing to menstrual iron losses;

4) During pregnancy, owing to the expanding blood volume of the mother, the demands of the fetus and placenta, and blood losses during childbirth.

The donation of 500 mL of blood produces a loss

of approximately 250 mg of iron. This is not a

significant problem in healthy, well-nourished

adults with adequate iron stores.

Dose/RDA

The RDA for iron is 10 mg for adult men, 15 mg for adult women, and 30 mg for pregnant women.

Most healthy individuals who self-medicate, including menstruating females, will absorb adequate iron from one 325-mg ferrous sulfate tablet per day. In a 325-mg ferrous sulfate tablet, 20% (about 60 mg) is elemental iron. In patients with iron deficiencies, 20% of the elemental iron (12 mg) may be absorbed.

Adverse Effects/Drug Interactions

All iron products tend to irritate the GI mucosa and may produce nausea, abdominal pain, and diarrhea.

These adverse effects may be minimized by reducing the dose or by giving iron with meals.

However, because food may decrease the amount of iron absorbed by as much as 50%, pharmacists may recommend iron with instructions for between-meal dosing.

4. SeleniumDescription

Selenium is present in all tissues.

Selenium is generally incorporated into organic compounds involving amino acids such as methionine or cysteine. Selenium compounds are about 80% absorbed.

The highest concentrations are found in the kidneys and liver; the lowest are in the lungs and brain. The kidney is the primary route of excretion.

Dietary sources of selenium include meat,

seafoods, and some cereal grains. Vegetables and

fruits contain little of this element.

The selenium content of foods depends on the

soils in which the plants are grown.

IndicationsSelenium is an essential trace element in humans, but

deficiencies are not common in the general population. Selenium deficiency has been reported in patients

with alcoholic cirrhosis, probably owing to an insufficient diet or the altered metabolism of selenium.

Epidemiologic studies suggest that cancer and heart disease may be common in areas of low selenium availability.

Dose/RDA

The RDA for selenium has been set at 70 mcg for

adult men and 50-55 mcg for adult women.

Selenium is included in some multivitamin and

mineral preparations. It is available as 50-mcg

tablets and in various strengths in combination

products.

Adverse Effects/Drug Interactions

Toxic effects reported include loss of hair and

nails, skin lesions, and CNS and teeth involvement.

Selenium toxicity may be evidenced by growth

retardation, muscular weakness, infertility, focal

hepatic necrosis, bronchopneumonia, and

respiratory failure.

5. ZincDescription

Zinc is an integral part of at least 70 metalloenzymes, including carbonic anhydrase, lactic dehydrogenase, alkaline phosphatase, carboxypeptidase, aminopeptidase, and alcohol dehydrogenase.

It is also a cofactor in the synthesis of DNA and RNA, and it is involved in the mobilization of vitamin A from the liver and in the enhancement of follicle-stimulating hormone and luteinizing hormone.

It is essential for normal cellular immune functions and for spermatogenesis and normal testicular function, and it is important in the stabilization of membrane structure.

Most dietary zinc (about 70%) is derived from animal products. Good sources of zinc include liver; high-protein foods such as beef, lamb, legumes, and peanuts; and whole-grain cereals.

Indications

Symptoms of zinc deficiency include growth retardation, loss of appetite, skin changes, and immunologic abnormalities.

Additional symptoms of deficiency may include delayed sexual maturation, hypogonadism and hypospermia, alopecia, behavioral disturbances, night blindness, impaired taste and smell, and impaired wound healing.

Malabsorption syndromes, infection, myocardial infarction, major surgery, alcoholism, liver cirrhosis, high-fiber diets rich in phytate, pregnancy, and lactation predispose an individual to a suboptimal zinc status.

Iron supplements decrease zinc absorption just as zinc supplements decrease iron absorption, probably owing to competition for the same transport system.

Dose/RDA

The RDA for zinc is 15 mg and 12 mg for adult men and women, respectively.

The RDA for infants is 5 mg and for children, 10 mg.

Because zinc is only 10-40% absorbed from the GI tract, ingestion of 220-mg dose form of zinc sulfate (50 mg of elemental zinc) will supply 5-20 mg of zinc.

Zinc is available in various salt forms as capsules,

generally ranging in strength from 1.5 to 50 mg of

elemental zinc, and in numerous combination

products in various strengths.

Adverse Effects/Drug Interactions

The ingestion of 2 g or more of zinc sulfate has

resulted in GI irritation and vomiting.

Copper levels may be adversely affected by high

intake of zinc, and zinc may decrease tetracycline

absorption.

Because zinc may cause GI upset, it can be taken

with food.