Minerals are elements, substances composed of only one kind of atom. They’re inorganic (translation: They don’t contain the carbon, hydrogen, and oxygen atoms found in all organic compounds, including vitamins). Minerals occur naturally in nonliving things such as rocks and metal ores.

Although minerals also are present in plants and animals, they’re imported: Plants get minerals from soil; animals get minerals by eating plants. Most minerals have names reflecting the places where they’re found or characteristics such as their color.

For example, the name calcium comes from calx, the Greek word for “lime” (chalk), where calcium is found; chlorine comes from chloros, the Greek word for “greenish-yellow,” which just happens to be the color of the mineral. Other minerals, such as americium, curium, berkelium, californium, fermium, and nobelium, are named for where they were found or to honor an important scientist.

Think of your body as a house. Vitamins are like tiny little maids and butlers, scurrying about to turn on the lights and make sure that the windows are closed to keep the heat from escaping. Minerals are more sturdy stuff, the mortar and bricks that strengthen the frame of the house and the current that keeps the lights running.

Nutritionists classify the minerals essential for human life as either major minerals (including the principal electrolytes) or trace elements. Major minerals and trace elements are both minerals. The difference between them, nutritionally speaking, is how much you have in your body and how much you need to take in to maintain a steady supply.

Your body stores varying amounts of minerals but keeps more than 5 grams (about 1⁄6 of an ounce) of each of the major minerals and principal electrolytes on hand; you need to consume more than 100 milligrams a day of each major mineral to maintain a steady supply and to make up for losses. You store less than 5 grams of each trace element and need to take in less than 100 milligrams a day to stay even.

Some minerals interact with other minerals or with medical drugs. For example, calcium binds tetracycline antibiotics into compounds your body can’t break apart so that the antibiotic moves out of your digestive tract, unabsorbed and unused. That’s why your doctor warns you off milk and dairy products when you’re taking this medicine.

The following major minerals are essential for human beings:

• Calcium
• Phosphorus
• Magnesium
• Sulfur
• Sodium
• Potassium
• Chloride

Note: Sodium, potassium, and chloride, also known as the principal electrolytes.

Although sulfur, a major mineral, is an essential nutrient for human beings, it’s almost never included in nutritional books and/or charts. Why? Because it’s an integral part of all proteins. Any diet that provides adequate protein also provides adequate sulfur. After you’ve checked out proteins, come on back to look at the major minerals in minute detail.

Calcium - When you step on the scale in the morning, you can assume that about three pounds of your body weight is calcium, most of it packed into your bones and teeth. Calcium is also present in extracellular fluid (the liquid around body cells), where it performs the following duties:

• Regulating fluid balance by controlling the flow of water in and out of cells.
• Enabling cells to send messages back and forth from one to another.
• Keeping muscles moving smoothly and preventing cramping.

An adequate amount of calcium is important for controlling high blood pressure — and not only for the person who takes the calcium directly. At least one study shows that when a pregnant woman gets a sufficient amount of calcium, her baby’s blood pressure stays lower than average for at least the first seven years of life, meaning a lower risk of developing high blood pressure later on.

Your best food sources of calcium are milk and dairy products, plus fish such as canned sardines and salmon. Calcium also is found in dark green leafy vegetables, but the calcium in plant foods is bound into compounds that are less easily absorbed by your body.

Phosphorus - Like calcium, phosphorus is essential for strong bones and teeth. For tiptop performance, you need about half as much phosphorus as calcium. Phosphorus also enables a cell to transmit the genetic code (genes and chromosomes that carry information about your special characteristics) to the new cells created when a cell divides and reproduces.

In addition, phosphorus:

• Helps maintain the pH balance of blood (that is, keeps it from being too acidic or too alkaline)
• Is vital for metabolizing carbohydrates, synthesizing proteins, and ferrying fats and fatty acids among tissues and organs.
• Is part of myelin, the fatty sheath that surrounds and protects each nerve cell.

Phosphorus is in almost everything you eat, but the best sources are highprotein foods such as meat, fish, poultry, eggs, and milk. These foods provide more than half the phosphorus in a nonvegetarian diet; grains, nuts, seeds, and dry beans also provide respectable amounts.

Magnesium - Your body uses magnesium to make body tissues, especially bone. The adult human body has about an ounce of magnesium, and three-quarters of it is in the bones. Magnesium also is part of more than 300 different enzymes that trigger chemical reactions throughout your body. You use magnesium to:

• Move nutrients in and out of cells.
• Send messages between cells
• Transmit the genetic code (genes and chromosomes) when cells divide and reproduce.

An adequate supply of magnesium also is heart-healthy because it enables you to convert food to energy using less oxygen. Bananas are a good source of magnesium and so are many other plant foods, including dark green fruits and vegetables (magnesium is part of chlorophyll, the green pigment in plants), whole seeds, nuts, beans, and grains.

Trace Elements

Trace elements also are minerals, but they’re present in much, much smaller amounts. That’s why they are called trace minerals. You need just a trace. Get it? Good! Trace elements include:

• Iron
• Zinc
• Iodine
• Selenium
• Copper
• Manganese
• Fluoride
• Chromium
• Molybdenum

Iron - Iron is an essential constituent of hemoglobin and myoglobin, two proteins that store and transport oxygen. You find hemoglobin in red blood cells (it’s what makes them red). Myoglobin (myo = muscle) is in muscle tissue. Iron also is part of various enzymes.

Your best food sources of iron are organ meats (liver, heart, kidneys), red meat, egg yolks, wheat germ, and oysters. These foods contain heme (heme = blood) iron, a form of iron that your body can easily absorb. Whole grains, wheat germ, raisins, nuts, seed, prunes and prune juice, and potato skins contain nonheme iron.

Because plants contain substances called phytates, which bind this iron into compounds, your body has a hard time getting at the iron. Eating plant foods with meat or with foods that are rich in vitamin C (like tomatoes) increases your ability to split away the phytates and get iron out of plant foods.

Zinc - Zinc protects nerve and brain tissue, bolsters the immune system, and is essential for healthy growth. Zinc is part of the enzymes (and hormones such as insulin) that metabolize food, and you can fairly call it the macho male mineral.

The largest quantities of zinc in the male human body are in the testes, where it’s used in making a continuous supply of testosterone, the hormone a man needs to produce plentiful amounts of healthy, viable sperm. Without enough zinc, male fertility falters. So, yes, the old wives’ tale is true: Oysters — a rich source of zinc — are useful for men.

By the way, women also need zinc . . . just not as much as men do. How much is that? Other good sources of zinc are meat, liver, and eggs. Plenty of zinc is in nuts, beans, miso, pumpkin and sunflower seeds, whole-grain products, and wheat germ. But the zinc in plants, like the iron in plants, occurs in compounds that your body absorbs less efficiently than the zinc in foods from animals.

Iodine - Iodine is a component of the thyroid hormones thyroxine and triiodothyronine, which help regulate cell activities. These hormones are also essential for protein synthesis, tissue growth (including the formation of healthy nerves and bones), and reproduction.

The best natural sources of iodine are seafood and plants grown near the ocean, but modern Americans are most likely to get the iodine they need from iodized salt (plain table salt with iodine added). And here’s an odd nutritional note: You may get substantial amounts of iodine from milk. Are the cows consuming iodized salt?

No. The milk is processed and stored in machines and vessels kept clean and sanitary with iodates and iodophors, iodine-based disinfectants. Tiny trace amounts get into the products sent to the stores. Iodates are also used as dough conditioners (additives that make dough more pliable), so you’re also likely to find some iodine in most bread sold in supermarkets.

Selenium - Selenium was identified as an essential human nutrient in 1979 when Chinese nutrition researchers discovered that people with low body stores of selenium were at increased risk of Keshan disease, a disorder of the heart muscle with symptoms that include rapid heartbeat, enlarged heart, and (in severe cases) heart failure, a consequence most common among young children and women of childbearing age.

How does selenium protect your heart? One possibility is that it works as an antioxidant in tandem with vitamin E. A second possibility, raised by U.S. Department of Agriculture studies with laboratory rats, is that it prevents viruses from attacking heart muscle.

Here’s some exciting news: The results of a four-year study involving 1,312 patients previously treated for skin cancer strongly suggests that daily doses of selenium in amounts 3.8 times the current recommended daily allowance (RDA) (55 micrograms) may reduce the incidence of cancers of the lung, prostate, colon, and rectum.

The University of Arizona study was designed to see whether taking selenium lowered the risk of skin cancer. It didn’t. But among the patients who got selenium rather than a placebo, 45 percent fewer lung cancers, 58 percent fewer colon and rectal cancers, 63 percent fewer prostate cancers, and a 50 percent lower death rate from cancer overall were recorded.

Now a follow-up study will determine whether these results hold up. Although fruits and vegetables grown in selenium-rich soils are themselves rich in this mineral, the best sources of selenium are seafood, meat and organ meats (liver, kidney), eggs, and dairy products.

Copper - Copper is an antioxidant found in enzymes that deactivate free radicals (pieces of molecules that can link up to form compounds that damage body tissues) and make it possible for your body to use iron.

Copper also may play a role in slowing the aging process by decreasing the incidence of protein glycation, a reaction in which sugar molecules (gly = sugar) hook up with protein molecules in your bloodstream, twist the protein molecules out of shape, and make them unusable.

Protein glycation may result in bone loss, high cholesterol, cardiac abnormalities, and a slew of other unpleasantries. In people with diabetes, excess protein glycation may also be one factor involved in complications such as loss of vision. In addition, copper:

• Promotes the growth of strong bones.
• Protects the health of nerve tissue.
• Prevents your hair from turning gray prematurely But, no no, a thousand times, no: Large amounts of copper absolutely, and I repeat, absolutely will not turn gray hair back to its original color. Besides, megadoses of copper are potentially toxic.

You can get the copper you need from organ meats (such as liver and heart), seafood, nuts, and dried beans, including cacao beans (the beans used to make chocolate).

Manganese - Most of the manganese in your body is in glands (pituitary, mammary, pancreas), organs (liver, kidneys, intestines), and bones. Manganese is an essential constituent of the enzymes that metabolize carbohydrates and synthesize fats (including cholesterol).

Manganese is important for a healthy reproductive system. During pregnancy, manganese speeds the proper growth of fetal tissue, particularly bones and cartilage. You get manganese from whole grains, cereal products, fruits, and vegetables. Tea is also a good source of manganese.

Fluoride - Fluoride is the form of fluorine (an element) in drinking water. Your body stores fluoride in bones and teeth. Although researchers still have some questions about whether fluoride is an essential nutrient, it’s clear that it hardens dental enamel, reducing your risk of getting cavities.

In addition, some nutrition researchers suspect (but cannot prove) that some forms of fluoride strengthen bones. Small amounts of fluoride are in all soil, water, plants, and animal tissues. You also get a steady supply of fluoride from fluoridated drinking water.

Chromium - Very small amounts of trivalent chromium, a digestible form of the very same metallic element that decorates your car and household appliances, are essential for several enzymes that you need to metabolize fat.

Chromium is also a necessary partner for glucose tolerance factor (GTF), a group of chemicals that enables insulin (an enzyme from the pancreas) to regulate your use of glucose, the end product of metabolism and the basic fuel for every body cell.

In a recent joint study by USDA and the Beijing Medical University, adults with noninsulin-dependent diabetes who took chromium supplements had lower blood levels of sugar, protein, and cholesterol, which are all good signs for people with diabetes.

In a related study, chromium reduced blood pressure in laboratory rats bred to develop hypertension (high blood pressure), a common complication in diabetes. Right now, little information exists about the precise amounts of chromium in specific foods. Nonetheless, yeast, calves’ liver, American cheese, wheat germ, and broccoli are regarded as valuable sources of this trace element.

Molybdenum - Molybdenum (pronounced mo-lib-de-num) is part of several enzymes that metabolize proteins. You get molybdenum from beans and grains. Cows eat grains, so milk and cheese have some molybdenum. Molybdenum also leeches into drinking water from surrounding soil. The molybdenum content of plants and drinking water depends entirely on how much molybdenum is in the soil.