Dietary sources and functions of major Minerals

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Chemical analysis shows that the human body is made up of specific chemical elements. Four of these elements—oxygen, carbon, hydrogen, and nitrogen— make up 96% of body weight. All the remaining elements are minerals, which represent only 4% of body weight. Nevertheless, these minerals are essential for good health.

A mineral is an inorganic element necessary for the body to build tissues, regulate body fluids, or assist in various body functions. Minerals are found in all body tissues. Any abnormal concentration of minerals in the blood can help diagnose different disorders. Minerals cannot provide energy by themselves, but in their role as body regulators, they contribute to the production of energy within the body.

Minerals are found in water and in natural (unprocessed) foods, together with proteins, carbohydrates, fats, and vitamins. Minerals in the soil are absorbed by growing plants. Humans obtain minerals by eating plants grown in mineral-rich soil or by eating animals that have eaten such plants. The specific mineral content of food is determined by burning the food and then chemically analyzing the remaining ash.

Highly processed or refined foods such as sugar and white flour contain almost no minerals. Iron, together with the vitamins thiamine, riboflavin, niacin, and folate, are commonly added to white flour and cereals, which are then labeled enriched foods.

Most minerals in food occur as salts, which are soluble in water. Therefore, the minerals leave the food and remain in the cooking water. Foods should be cooked in as little water as possible or, preferably, steamed, and any cooking liquid should be saved to be used in soups, gravies, and white sauces. Using this liquid improves the flavor as well as the nutrient content of foods to which it is added.

CLASSIFICATION

Minerals are divided into two groups. They are the major minerals, so named because each is required in amounts greater than 100 mg a day, and the trace minerals, which are needed in amounts smaller than 100 mg a day.

Electrolytes are essential in maintaining the body’s fluid balance, and they contribute to its electrical balance, assist in its transmission of nerve impulses and contraction of muscles, and help regulate its acid-base balance.

Normally, a balanced diet will maintain electrolyte balance. However, in cases of severe diarrhea, vomiting, high fever, or burns, electrolytes are lost, and the electrolyte balance can be upset. Medical intervention will be necessary to replace the lost electrolytes.

Scientists lack exact information on some of the trace elements, although they do know that trace elements are essential to good health. The study of these elements continues to reveal their specific relationships to human nutrition. A balanced diet is the only safe way of including minerals in the amounts necessary to maintain health.

Category Age Copper (µg) Manganese (mg) Chromium (µg) Molybdenum (µg)
Infants 0–0.6 months 200 0.003 0.2 2
7–12 months 220 0.6 5.5 3
Children and adolescents 1–3 years 340 1.2 11 17
4–8 years 440 1.5 15 22
9–13 years 700 1.9 21–25 34
Adults 14–18 years 890 2.2 24–35 43
19–70 years 900 1.8–2.3 25–36 45

 

The Food and Nutrition Board of the National Academy of Sciences–National Research Council (hereafter NRC) has recommended dietary allowances for minerals where research indicates knowledge is adequate to do so.

For those minerals where there remains some uncertainty as to amounts of specific human requirements, the NRC has provided a table of Adequate Intakes of selected minerals. The NRC recommends that the upper levels of listed amounts not be habitually exceeded. In addition, the Institute of Medicine has developed Daily Reference Intakes (DRIs) for calcium, fluoride, phosphorus, and magnesium. The DRI incorporates Estimated Average Requirements (EAR), the RDA, and Tolerable Upper Intake Levels.

TOXICITY

Because it is known that minerals are essential to good health, some would-be nutritionists will make claims that “more is better.” Ironically, more can be hazardous to one’s health when it comes to minerals. In a healthy individual eating a balanced diet, there will be some normal mineral loss through perspiration and saliva, and amounts in excess of body needs will be excreted in urine and feces. However, when concentrated forms of minerals are taken on a regular basis, over a period of time, they become more than the body can handle, and toxicity develops. An excessive amount of one mineral can sometimes cause a deficiency of another mineral. In addition, excessive amounts of minerals can cause hair loss and changes in the blood, hormones, bones, muscles, blood vessels, and nearly all tissues. Concentrated forms of minerals should be used only on the advice of a physician.

Major Minerals

Name Food sources Functions Deficiency/toxicity
Calcium (Ca++) Milk, cheese

Sardines

Salmon

Some dark green, leafy vegetables

Development of bones and teeth

Transmission of nerve impulses

Blood clotting

Normal heart action

Normal muscle activity

Deficiency

Osteoporosis

Osteomalacia

Rickets

Tetany

Retarded growth

Poor tooth and bone formation

Phosphorus (P) Milk, cheese

Lean meat

Poultry

Fish

Whole-grain cereals

Legumes

Nuts

Development of bones and teeth

Maintenance of normal acid-base balance of the blood

Constituent of all body cells

Necessary for effectiveness of some vitamins

Metabolism of carbohydrates, fats, and proteins

Deficiency

Poor tooth and bone formation

Weakness

Anorexia

General malaise

Potassium (K+) Oranges

Bananas

Dried fruits

Vegetables

Legumes

Milk

Cereals

Meat

Contraction of muscles

Maintenance of fluid balance

Transmission of nerve impulses

Osmosis

Regular heart rhythm

Cell  metabolism

Deficiency

Hypokalemia

Muscle weakness

Confusion

Abnormal heartbeat

Toxicity

Hyperkalemia

Potentially life threatening irregular heartbeats

 

Sodium (Na+) Table salt,

Beef, eggs

Poultry

Milk, cheese

Maintenance of fluid balance

Transmission of nerve impulses

Osmosis

Acid-base balance

Regulation of muscle and nerve irritability

 

Deficiency

Nausea

Exhaustion

Muscle cramps

Toxicity

Increase in blood pressure

Edema

Chloride (Cl-) Table salt

Eggs

Seafood

Milk

Gastric acidity

Regulation of osmotic pressure

Osmosis

Fluid balance

Acid-base balance

Formation of hydrochloric acid

Deficiency

Imbalance in gastric acidity

Nausea

Exhaustion

Magnesium (Mg++) Green, leafy vegetables

Whole grains

Avocados

Nuts

Milk

Legumes

Bananas

Synthesis of ATP

Transmission of nerve impulses

Activation of metabolic enzymes

Constituent of bones, muscles, and red blood cells

Necessary for healthy muscles and nerves

Deficiency

Normally unknown

Mental, emotional, and

muscle disorders

Sulfur (S) Eggs

Poultry

Fish

Maintenance of protein structure

For building hair, nails, and all body tissues

Constituent of all body cells

Unknown
Iron (Fe+) Muscle meats

Poultry

Shellfish

Liver

Legumes

Dried fruits

Whole-grain or enriched breads and cereals

Dark green and leafy vegetables

Molasses

Transports oxygen and carbon dioxide

Component of hemoglobin and myoglobin

Component of cellular enzymes essential for energy production

 

Deficiency

Iron deficiency anemia characterized by weakness, dizziness, loss of weight, and pallor

Toxicity

Hemochromatosis (genetic)

Can be fatal to children

May contribute to heart disease

Injure liver

Iodine (I-) Iodized salt

Seafood

Regulation of basal metabolic rate

 

Deficiency

Goiter

Cretinism

Myxedema

Zinc (Zn+) Seafood, especially oysters

Eggs

Milk

Wheat bran

Legumes

Formation of collagen

Component of insulin

Component of many vital enzymes

Wound healing

Taste acuity

Essential for growth

Immune reactions

Deficiency

Dwarfism, hypogonadism, anemia

Loss of appetite

Skin changes

Impaired wound healing

Decreased taste acuity

Selenium (Se-) Seafood

Kidney

Liver

Muscle meats

Grains

Constituent of most body tissue

Needed for fat metabolism

Antioxidant functions

Deficiency

Unclear, but related to Keshan disease

Muscle weakness

Toxicity

Vomiting

Loss of hair and nails

Skin lesions

Copper (Cu+) Liver

Shellfish, oysters

Legumes

Nuts

Whole grains

Essential for formation of hemoglobin and red blood cells

Component of enzymes

Wound healing

Needed metabolically for the release of energy

Deficiency

Anemia

Bone disease

Disturbed growth and metabolism

Toxicity

Vomiting; diarrhea

Wilson’s disease (genetic)

 

Manganese (Mn+) Whole grains

Nuts

Fruits

Tea

Component of enzymes

Bone formation

Metabolic processes

Deficiency

Unknown

Toxicity

Possible brain disease

Fluoride (F-) Fluoridated water

Seafood

Increases resistance to tooth decay

Component of bones and teeth

Deficiency

Tooth decay

Possibly osteoporosis

Toxicity

Discoloration of teeth

(mottling)

Chromium (Cr) Meat

Vegetable oil

Whole-grain cereal and nuts

Yeast

Associated with glucose and lipid metabolism Deficiency

Possibly disturbances of glucose metabolism

Molybdenum (Mo) Dark green, leafy vegetables

Liver

Cereal

Legumes

Enzyme functioning

Metabolism

Deficiency

Unknown

Toxicity

Inhibition of copper absorption

 

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