Dietary sources and functions of major Minerals

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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