That's not the only mineral getting a closer look. From calcium to zinc, essential minerals appear to be worth their weight in nutritional gold. In some cases they may help you achieve a healthy weight, too.

"If I were a betting lady, I would bet on getting some of the minerals to keep me healthier," said Judith S. Stern, professor of nutrition and internal medicine at the University of California-Davis, where the research center is.

That's because growing evidence points to the blood-pressure-lowering benefits of potassium, possible diabetes prevention from magnesium and potential immune system boosting from zinc.

Stern and other nutrition experts say that food is the leading choice to meet mineral requirements.

So to help you dig for your daily minerals, here's a guide to the gems and the foods that deliver them.

• Calcium: The most common mineral in the body, calcium is best known for building strong bones and teeth. It also plays a key role in maintaining blood vessels, producing hormones and enabling nerves to signal each other. Growing evidence suggests that it may help with weight control, keep blood pressure in check and reduce the risk of colon polyp recurrence, a risk factor for colon cancer. The U.S. Dietary Guidelines Advisory Committee recently noted that many Americans fall short on calcium.

Kids and teens need the most — about 1,300 milligrams per day. Adults 51 and older require 1,200 milligrams per day; those 50 and under need 1,000 milligrams.

• Food sources: Low-fat and nonfat dairy products; fish with bones, such as canned salmon; fortified food, including juice and soy milk; and some green vegetables, such as spinach.

• Copper: Too little copper appears to depress the immune function and weaken bones. Too much may help promote heart disease. Aim for 900 micrograms per day for adults, 19 and older. That's equal to about a cup of lentil soup and an ounce of cashews.

• Food sources: Oysters, crab and other shellfish; liver; almonds and other nuts; lentils, mushrooms, shredded wheat and chocolate.

• Iron: Without it, blood could not carry oxygen, protein would not form and key biochemical reactions throughout the body would not occur. Iron bolsters the immune system and is required for growth and reproduction, which is why pregnant women need the most: 27 milligrams per day. Women of childbearing ages need about 18 milligrams per day; men 19 and older and post-menopausal women need the least: eight milligrams per day — about that found in 3/4 cup of tofu.

• Food sources: Beef, dark chicken meat, oysters, raisin bran, black strap molasses and prunes. Beans, soy and spinach are rich in iron, but also have phytates, which can cut iron absorption in half; this is why vegetarians are urged to eat more iron-rich food than meat-eaters. Vitamin C helps boost iron absorption, so drink some orange juice with your raisin bran for better absorption.

• Magnesium: Key to hundreds of vital functions, magnesium helps maintain muscle, bone and nerves, and promotes a steady heartbeat. The latest findings suggest it may help prevent migraine headaches, could help reduce asthma and may treat impaired glucose tolerance, a precursor of diabetes. Men 19 and older need the most, about 400 milligrams per day, equal to about an ounce of almonds, a bowl of high-fiber cereal, a cup of brown rice and a bowl of black-eyed peas. Women need about 300 milligrams per day.

• Food sources: Whole grains, especially bran cereals; nuts and green vegetables, including spinach.

• Potassium: Vital to the internal integrity of all cells in the body, potassium is also key for controlling blood pressure. Too little potassium can cause fatigue, muscle cramps, bloating and, in severe cases, fatal irregular heartbeats. New research suggests potassium may help prevent stroke, osteoporosis and kidney stones. Those 14 and older need nearly five grams per day.

• Food sources: Fruit (especially bananas and oranges), vegetables (especially potatoes) and nuts.

• Zinc: Important to protect against infection, preserve brain function and for reproduction, zinc is a key element of enzymes, enables protein production and allows communication between cells. Too little zinc can cause rashes, delay puberty, impair hearing, reduce appetite, cause night blindness and produce severe diarrhea. New research suggests zinc may help treat the common cold and could be helpful in diabetes, macular degeneration and bolstering the immune systems of those with HIV. Aim for 11 milligrams per day for men, 19 and older; eight milligrams for women. That's equal to about six oysters. Just don't regularly exceed the tolerable upper limit of 40 milligrams per day for adults 19 and older, since too much zinc over a long period can cause toxicity, including copper deficiency, diarrhea and vomiting.