Why do I need Calcium?
Calcium is the primary mineral in bones and teeth. It must be consumed; the body cannot produce it. Calcium also plays a vital role in daily body functions such as:

• muscle contraction and relaxation
• blood clotting
• the transmission of nerve impulses.

The calcium in our bones is in a constant state of turnover. When diet does not provide enough, the body draws on the calcium stored in bone to maintain adequate blood levels. Not consuming enough calcium daily can drain calcium from bones, leading to osteoporosis. Other dietary factors can increase the calcium lost in the urine. Including calcium in your daily diet is one major way to stay in positive calcium balance and reduce your risk for osteoporosis.

How much calcium do I need?
Recommended Dietary Allowances (RDAs) for calcium have been established based on Life Stage Groups. They reflect differences in bone growth rates and include amounts necessary to replace daily losses. Medical conditions can also change calcium requirements. People with shortened intestines, or those on prednisone or cortisone-like medications (often taken for asthma or rheumatoid arthritis) can have calcium absorption problems. Most Americans do not meet their RDA for calcium with their diet.

Is it possible to take too much calcium?
Yes. There is rarely any advantage in taking more than 1500 mg a day. Taking 2000-2500mg a day, (from food and/or supplements) can interfere with the absorption of zinc, iron and magnesium and may increase the risk of kidney stones.

Where do I get calcium?
It's best to try to get the calcium you need from food. Most people know that dairy products are among the richest sources of calcium.

• Nonfat and low-fat dairy products have as much calcium as those made from whole milk.
• Milk’s added Vitamin D (100 IU/cup) and natural lactose (the natural sugar in milk) also help your body absorb the calcium. (Generally we absorb about 30% of the calcium in most foods, including dairy.)

Other sources of calcium include:

•     green leafy vegetables, (like bok choy, collards, and kale)
•     sardines
•     broccoli
•     most tofu
•     calcium-fortified orange juice
•     fortified cereals.

Note: on a food label, calcium is generally expressed as a percentage of the 1,000 mg a day U.S. RDA. Therefore, “20%” would provide 200 mg per serving. For non-dairy eaters, consult the Calcium Content list, and if necessary, consider a supplement.

Other Factors: Positive Calcium Balance
Exercise that causes muscles to tug at bones, or is weight bearing, also helps keep bones strong. Good examples are walking, low-impact aerobics and dancing.

Vitamin D is key to calcium absorption. Vitamin D is manufactured in the skin following exposure to sunlight*. This varies, however, with:

• time of day
• season
• latitude
• skin pigmentation
• use of sunscreen
• age

It is estimated that 30-40% of adults over 50 are vitamin D-deficient. Vitamin D deficiency accelerates bone loss and increases the risk of fractures.

The current daily recommended allowance for vitamin D is 200 to 600 international units (IU), depending upon age. Most experts now recommend a total of 1,000 to 2,000 IU per day from all sources -sun, diet and supplements. People with limited sun exposure should probably take supplements. When choosing a supplement, look for one that contains vitamin D3 (cholecalciferol).
Note:Sunlight in Cambridge, MA provides inadequate vitamin D between October and April.