Minerals are necessary for the normal functioning of the body's cells. The body needs large quantities of calcium, chloride, magnesium, phosphate, potassium, and sodium. These minerals are called macrominerals. Bone, muscle, heart, and brain function depends on these minerals. The body needs small quantities of chromium, copper, fluoride, iodine, iron, manganese, molybdenum, selenium, and zinc. These minerals are called trace minerals. Except for chromium, all trace minerals are incorporated into enzymes or hormones required in body processes (metabolism). Chromium helps the body keep blood sugar levels normal. All trace minerals are harmful if too much is ingested.

Minerals are an essential part of a healthy diet. The recommended dietary allowance (RDA)—the amount most healthy people need each day to remain healthy—has been determined for most minerals. People who have a disorder may need more or less than this amount.

Consuming too little or too much of certain minerals can cause a nutritional disorder. People who eat a balanced diet containing a variety of foods are unlikely to develop a nutritional disorder or a major mineral deficiency, except for calcium, iodine, or iron deficiency. However, people who follow restrictive diets may not consume enough of a particular mineral (or vitamin). For example, vegetarians, including those who eat eggs and dairy products, are at risk of iron deficiency. Infants are more likely to develop deficiencies because they are growing rapidly (thus requiring large amounts of nutrients).

Consuming large amounts (megadoses) of mineral supplements without medical supervision may have harmful (toxic) effects.

Electrolytes: Some minerals—especially the macrominerals—are important as electrolytes. The body uses electrolytes to help regulate nerve and muscle function and to maintain acid-base balance (see Acid-Base Balance: Introduction) and fluid balance.

To function normally, the body must keep fluid levels from varying too much in the areas of the body that contain fluid (called compartments). The three main compartments are

• Fluid within cells
• Fluid in the space around cells
• Blood

The kidneys help maintain electrolyte concentrations by filtering electrolytes from blood, returning some electrolytes, and excreting any excess into the urine. Thus, the kidney help maintain a balance between daily consumption and excretion.

If the balance of electrolytes is disturbed, disorders can develop. An electrolyte imbalance can result from the following:

• Becoming dehydrated
• Taking certain drugs
• Having certain heart, kidney, or liver disorders
• Being given intravenous fluids or feedings in inappropriate amounts

Diagnosis

Doctors can detect many common nutritional disorders or an electrolyte imbalance by measuring the levels of minerals in a sample of blood or urine.

Minerals Mineral Good Sources Main Functions Recommended Dietary Allowance for adults Safe Upper Limit Calcium Milk and milk products, meat, fish eaten with the bones (such as sardines), eggs, fortified cereal products, beans, fruits, and vegetables Required for the formation of bone and teeth, for blood clotting, for normal muscle function, for the normal functioning of many enzymes, and for normal heart rhythm 1,000 milligrams 1,200 milligrams for people over 50 2,500 milligrams Chloride Salt, beef, pork, sardines, cheese, green olives, corn bread, potato chips, sauerkraut, and processed or canned foods (usually as salt) Involved in electrolyte balance 1,000 milligrams — Chromium Liver, processed meats, whole-grain cereals, and nuts Enables insulin to function (insulin controls blood sugar levels) Helps in the processing (metabolism) and storage of carbohydrates, protein, and fat 35 micrograms for men aged 50 and younger 25 micrograms for women aged 50 and younger 30 micrograms for men over 50 20 micrograms for women over 50 — Copper Organ meats, shellfish, cocoa, mushrooms, nuts, dried legumes, dried fruits, peas, tomato products, and whole-grain cereals Is a component of many enzymes that are necessary for energy production, for antioxidant action*, and for formation of the hormone epinephrine, red blood cells, bone, and connective tissue 900 micrograms 10,000 micrograms Fluoride Seafood, tea, and fluoridated water Required for the formation of bone and teeth 3 milligrams for women 4 milligrams for men 10 milligrams Iodine Seafood, iodized salt, eggs, cheese, and drinking water (in amounts that vary by the iodine content of local soil) Required for the formation of thyroid hormones 150 micrograms 1,100 micrograms Iron As heme† iron: Beef, poultry, fish, kidneys, and liver As nonheme iron: Soybean flour, beans, molasses, spinach, clams, and fortified grains and cereals Required for the formation of many enzymes in the body Is an important component of muscle cells and of hemoglobin, which enables red blood cells to carry oxygen and deliver it to the body's tissues 8 milligrams for women over 50 and for men 18 milligrams for women aged 50 and younger (premenopause) 27 milligrams for pregnant women 9 milligrams for breastfeeding women 45 milligrams Magnesium Leafy green vegetables, nuts, cereal grains, beans, and tomato paste Required for the formation of bone and teeth, for normal nerve and muscle function, and for the activation of enzymes 320 milligrams for women 420 milligrams for men — Manganese Whole-grain cereals, pineapple, nuts, tea, beans, and tomato paste Required for the formation of bone and the formation and activation of certain enzymes 2.3 milligrams for men 1.8 milligrams for women 6 to 11 milligrams Molybdenum Milk, legumes, whole-grain breads and cereals, and dark green vegetables Required for metabolism of nitrogen, the activation of certain enzymes, and normal cell function Helps break down sulfites (present in foods naturally and added as preservatives) 45 micrograms 1,100 to 2,000 micrograms Phosphorus Dairy products, meat, poultry, fish, cereals, nuts, and legumes Required for the formation of bone and teeth and for energy production Used to form nucleic acids, including DNA (deoxyribonucleic acid) 700 milligrams 4,000 milligrams Potassium Whole and skim milk, bananas, tomatoes, oranges, melons, potatoes, sweet potatoes, prunes, raisins, spinach, turnip greens, collard greens, kale, other green leafy vegetables, most peas and beans, and salt substitutes (potassium chloride) Required for normal nerve and muscle function Involved in electrolyte balance 3.5 grams — Selenium Meats, seafood, nuts, and cereals (depending on the selenium content of soil where grains were grown) Acts as an antioxidant*, with vitamin E Required for thyroid gland function 55 micrograms 400 micrograms Sodium Salt, beef, pork, sardines, cheese, green olives, corn bread, potato chips, sauerkraut, and processed or canned foods (usually as salt) Required for normal nerve and muscle function Helps the body maintain a normal electrolyte and fluid balance 1,000 milligrams 2,400 milligrams Zinc Meat, liver, oysters, seafood, peanuts, fortified cereals, and whole grains (depending on the zinc content of soil where grains were grown) Used to form many enzymes and insulin Required for healthy skin, healing of wounds, and growth 15 milligrams — *Antioxidants protect cells against damage due to reactive by-products of normal cell activity called free radicals. †The body absorbs heme iron better than nonheme iron.

Last full review/revision August 2008 by Larry E. Johnson, MD, PhD