You need calcium not only for strong bones and teeth, but also for normal blood clotting, and for healthy muscle and nervous system function. Most adults need around 1000 mg to 1200 mg every day (and teenagers need more). You can get enough calcium from the foods you eat.
Dairy products are one well-known as a source of calcium, but you don't need to consume dairy if you can't or don't want to, because you can get calcium from other foods too. Legumes, green leafy vegetables, nuts, seeds and bony fish (like canned salmon) are contain calcium. And don't forget your vitamin D. If you don't get enough sun exposure (up to 30 minutes twice each week), then you might want to consider taking vitamin D supplements.
Calcium is a major mineral and is the most abundant mineral in the human body. Most of it is stored in the bones and teeth (about 99%), and the rest is blood, muscles and extracellular fluid.
Calcium is necessary for strong bones and teeth, plus it plays an important role in blood clotting, muscle contraction, hormonal secretion and normal nervous system function.
Your body constantly breaks down and rebuilds your bones to keep them strong. When you're young, your body builds up calcium as fast as it removed it from the bones. But when you get older, your body tends to resorb more calcium than it puts back so you're at a greater risk for osteoporosis.
Ages 1-3: 700 milligrams (mg) per day
Ages 4-8: 1000 mg per day
Ages 9-18: 1300 mg per day
Men ages 19-70: 1000 mg per day
Women ages 19-50: 1000 mg per day
Women ages 51 and older: 1200 mg per day
Men ages 71 and older: 1200 mg per day
Calcium supplements are often recommended for adult females to help prevent osteoporosis. They are generally safe, however, taking more than 2500 mg per day on a regular basis may lead to hypercalcemia, kidney problems and may impair the absorption of other minerals. Calcium supplements may interact with several medications, so consult your doctor before taking supplements if you are also taking medications.
Calcium is found in dairy products such as milk, cheese, and yogurt, as well as dark green vegetables, whole sardines and calcium-fortified foods. Your body needs vitamin D in order to absorb and use calcium.
Article courtesy of nutrition.about.com, found here.