Calcium (a chemical element whose symbol in the periodic table of the elements is Ca) is the most plentiful mineral in the human body. Calcium is vital for bone heath, but, in addition to building strong bones, calcium is essential for the heart, muscles and nerves to function properly and for blood to clot.

Calcium is the mineral in your body that is stored by your bones and keeps them strong. Ninety-nine percent of the calcium in your body is stored in your bones and teeth. The remaining 1% is in your blood and soft tissues and is essential for life and health. Without this tiny 1% of calcium, your muscles wouldn’t contract correctly, your blood wouldn’t clot and your nerves wouldn’t carry messages.

There are only two ways you can get this essential 1% of circulating calcium:

• From the calcium in your diet
• From the calcium in your bone

It is mainly the calcium in your diet that spares, or protects, the calcium in your bones. In addition to their structural role, your bones are your emergency supply of calcium. Your body actually tears down and builds bone all of the time. If you don’t get enough calcium from the food you eat, your body automatically takes the calcium you need from your bones. If your body continues to tear down more bone than it replaces over a period of years, your bones can become weak and break easily. This leads to the crippling bone disease called "osteoporosis." According to the Surgeon General’s Report on Bone Health and Osteoporosis , approximately 34 million Americans have reduced bone mass and ten million have osteoporosis. Eighty percent of those with osteoporosis are women and 20% are men. Half of women and one quarter of men over the age of 50 will have osteoporosis-related fracture sometime during their lifetime.

How Do You Know If Calcium Is Working?

There are several ways for doctors to measure bone health. One way is by testing for chemical markers in the blood and urine. These “markers” give doctors an idea of your bone mineral density and whether you are at risk for a fracture. This science is still in development, but studies have begun to show us how soon calcium starts to work in the body and its lasting effects:

		Within 24 hours of taking a calcium supplement, bone markers show a significant change.
		In as little as 5 days, increase in calcium intake is accompanied by a reduced rate of “bone resorption,” or breakdown of your bone.
		In 14 days, calcium supplementation can reduce urinary excretion of pyridinoline and deoxypyridinoline, which are important markers of bone breakdown.
		After 3 months, doctors have shown increased bone mineral density.
		After 1 year of taking supplements, doctors have shown significantly increased bone mineral density.
		An analysis of trials representing almost 2,000 post-menopausal participants demonstrated that calcium was more effective than placebo in reducing rates of bone loss after 2 or more years of supplementation.