Calcium is an essential mineral needed by the body to build strong bones and to keep them strong throughout your life. Calcium is also needed for other purposes, such as muscle contraction.

Almost all calcium (99 percent) is stored in the bones. The remaining one percent circulates in the body. If the body does not get enough calcium from the food you eat to keep the right amount circulating in the blood, you body will take calcium from the bones. Hundreds of scientific studies show that over time, the loss of calcium from bones can lead to the bone disease "osteoporosis", sometimes called "brittle bones," which can lead to thinner bones and greater risk of bone fractures.

Everybody needs calcium to build and keep strong bones and for normal body functioning. But some people are at greater risk of getting osteoporosis as they get older. The risk is higher for women than men, especially women who have smaller bones. To reduce the risk of osteoporosis, you have to eat enough calcium during childhood and young adulthood, when bone mass is formed. As an adult, the calcium you eat helps you to keep the bone mass you developed when you were growing.

Foods that are good sources of calcium include dairy products, such as milk, yogurt and cheese and dark green leafy vegetables, such as kale and turnip greens. There are also some foods that add calcium, such as calcium-fortified orange juice and grapefruit juice.

Based on many years of scientific study, nutrition experts have learned how much calcium people need to eat every day to build strong bones and maintain their bone mass as they get older. The amount you need to eat depends on things like your age. For example:

Children 9 to 18 years old - 1,300 milligrams (mg)

Adults 19 to 50 years old - 1,000 milligrams (mg)

Adults over 50 - 1,200 milligrams (mg)

Although it is possible to eat too much calcium (more than 2,500 milligrams every day), studies have shown that most Americans do not eat the recommended amount of calcium they need each day.

If you are lactose intolerant, it can be hard to get enough calcium. Lactose intolerance means the body is not able to easily digest foods that contain lactose, or the sugar that is found in dairy products like milk. Gas, bloating, stomach cramps, diarrhea, and nausea are symptoms you might have. It can start at any age but often begins as we grow older.

Lactose-reduced and lactose-free products are sold in food stores. There's a great variety, including milk, cheese, and ice cream. Found at the grocery store or drug store, you also can take special pills or liquids before eating to help you digest dairy foods.

You can also eat foods that have calcium added (fortified), like some cereals and orange juice. Also think about taking calcium pills. But talk to your doctor or nurse first to see which one is best for you. Please note: If you have symptoms of lactose intolerance, see your doctor or nurse. These symptoms could also be from a different, or more serious, illness.