Calcium

Calcium is the most abundant mineral in the human body and is an important component of a healthy diet. It is essential for the normal growth and maintenance of bones and teeth. In addition, it plays an important part in muscle contraction, oocyte activation, blood clotting, nerve impulse transmission, regulating heartbeat, and fluid balance within cells. Calcium requirements must be met throughout life, but requirements are greatest during periods of growth, such as childhood, during pregnancy and when breast-feeding. vitamin D is needed to absorb calcium.
Long-term calcium deficiency can lead to osteoporosis, in which the bone deteriorates and there is an increased risk of fractures. Overretention, on the other hand, can cause kidney stones.
Milk, yogurt, cheese and other dairy products are a prime source of calcium and are also fortified with vitamin D. Calcium needs can be met by consuming at least three or four servings of dairy products daily. It should be noted that some dairy products, such as hard cheese and whole milk, contain significant amounts of saturated fat, which can contribute to cardiovascular disease. Therefore, a diet consisting of low-fat dairy products should be considered. Recommended daily calcium intake varies from 1,000 to 1,500 milligrams (mg), depending upon the person's stage of life.
Some individuals are allergic to dairy products and even more people, particularly those of non-European descent, are lactose-intolerant, leaving them unable to consume dairy products. Fortunately, there are many other good sources of calcium. These include: seaweeds such as kelp, wakame, and hijiki; nuts and seeds, including almonds and sesame; beans; seafood, such as oysters and shrimp; soft-boned fish; amaranth; whole wheat; collard greens; okra; rutabaga; and broccoli. In addition, several products are fortified with calcium, including soya milk, rice milk, orange juice, and bread.

Dietary calcium supplements

In the United States, between about 50 percent and 75 percent of adults do not get sufficient calcium in their diet.^[1] For this reason, individuals may consider taking dietary calcium supplements.

• Calcium carbonate is the most common and least expensive calcium supplement. It can be difficult to digest and causes gas in some people. Taking magnesium with it can help to prevent constipation. Calcium carbonate is 40 percent elemental calcium, which means that 1,000 mg will provide 400 mg of calcium. Taking this supplement with food can aid in absorption.

• Calcium citrate is more easily absorbed (bioavailability is 2.5 times higher than calcium carbonate), easier to digest, and less likely to cause constipation and gas than calcium carbonate. It also has a lower risk of contributing to the formation of kidney stones. Calcium citrate is 21 percent elemental calcium, which means that 1,000 mg will provide 210 mg of calcium. It is more expensive than calcium carbonate and more of it must be taken to get the same amount of calcium.

• Calcium phosphate costs more than calcium carbonate, but less than calcium citrate. It is easily absorbed and is less likely to cause constipation and gas than either.

• Calcium lactate and calcium aspartate are more easily digested but more expensive than calcium carbonate.

There are conflicting recommendations about when to take calcium supplements. However, most experts agree that no more than 500 mg should be taken at a time—any excess will go to waste. It is recommended to spread doses throughout the day, with the last dose near bedtime.

Adapted from:
http://www.newworldencyclopedia.org/entry/Calcium