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Calcium
Calcium is a mineral most often associated with healthy bones and teeth, although it also plays an important role in blood clotting, helping muscles to contract, and regulating normal heart rhythms and nerve functions. About 99% of the body’s calcium is stored in bones, and the remaining 1% is found in blood, muscle, and other tissues.

In order to perform these vital daily functions, the body works to keep a steady amount of calcium in the blood and tissues. If calcium levels drop too low in the blood, parathyroid hormone (PTH) will signal the bones to release calcium into the bloodstream. This hormone may also activate vitamin D to improve the absorption of calcium in the intestines. At the same time, PTH signals the kidneys to release less calcium in the urine. When the body has enough calcium, a different hormone called calcitonin works to do the opposite: it lowers calcium levels in the blood by stopping the release of calcium from bones and signaling the kidneys to rid more of it in the urine.

The body gets the calcium it needs in two ways. One is by eating foods or supplements that contain calcium, and the other is by drawing from calcium in the body. If one does not eat enough calcium-containing foods, the body will remove calcium from bones. Ideally, the calcium that is “borrowed” from the bones will be replaced at a later point. But this doesn’t always happen and can’t always be accomplished just by eating more calcium.

Recommended Amounts

The Recommended Dietary Allowance (RDA) for calcium for women 19-50 years of age is 1,000 mg daily: for women 51+, 1,200 mg. For pregnant and lactating women, the RDA is 1,000 mg. For men 19-70 years of age, the RDA is 1,000 mg: for men 71+ years, 1,200 mg.

Calcium and Health

The reviews below specifically looked at the effect of calcium on various health conditions. Scroll down for links to more information on the health effects of specific foods rich in calcium.

Calcium is one of the most important nutrients required for bone health. Bone is living tissue that is always in flux. Throughout the lifespan, bones are constantly being broken down and built up in a process known as remodeling. Bone cells called osteoblasts build bone, while other bone cells called osteoclasts break down bone if calcium is needed. In healthy individuals who get enough calcium and physical activity, bone production exceeds bone destruction up to about age 30. After that, destruction typically exceeds production. This is sometimes called “negative calcium balance,” which can lead to bone loss. Women tend to experience greater bone loss than men later in life due to menopause, a condition that lowers the number of hormones that help to build and preserve bone.

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