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The Role of Calcium in the Human Body

Calcium is a mineral necessary to build and maintain strong bones and teeth, which also aids a number of other body processes. These include blood clotting, blood vessel and muscle contraction, enzyme and hormone secretion and the central nervous system functioning. Calcium happens to be the body’s most common mineral. On average, calcium makes up about 2.3% of a person’s body weight.

Nearly all calcium in the body is stored in bones. Its role is to help bones to remain strong and stiff enough to carry the weight of the body. When needed, the body can draw upon these calcium reserves in the bones and use it elsewhere, such as in the bloodstream and soft tissues.

Calcium is a mineral and so it cannot be produced by the body. Therefore, consuming adequate levels of calcium is crucial. The body needs a constant supply of calcium from diet to keep bones growing and strong. Bone remodelling is an ongoing process in which bone is broken down and calcium is deposited to replace the bone material that is lost. However, when the amount of calcium in the bloodstream is too low, calcium stored in bones is broken down and used in the bloodstream. This may lead to the calcium depletion in bones, a process that can take many years.

During childhood, people undergo a great amount of bone formation. Most individuals can continue to build bone mass until their mid-30s. However, after age 35, they can only slow the bone loss, which is a natural part of aging. Bone loss accelerates especially in women following menopause.

By eating diets high in calcium early in life, children and adolescents should try to build peak bone mass. This can help reduce the risk of fractures and osteoporosis in later life. Weight-bearing exercises can help to maximize bone strength and bone density. Although people cannot build new bone after age 35, appropriate calcium intake (especially in conjunction with vitamin D) and engaging in weight-bearing exercises can help them to hold on or significantly slow the loss of the bone mass they have.

RDAs for Calcium

The recommended Dietary Allowances (RDAs) for calcium are 1,300mg per day for older children and teens aged 9-18, 1,000mg per day for adults aged 19-50 and 1,200mg per day for the elderly over the age of 70. However, women should increase their intake of calcium to 1,200mg per day already in their fifties (men only after the age of 70). The tolerable upper intake levels for teens are 3,000mg per day and 2,500mg per day for adults. Excessively high intakes of calcium may result in hypercalcemia, decreased absorption of other minerals and impaired kidney function.

Health Benefits of Calcium

As it was mentioned earlier, calcium’s major role in the body is to help bones grow and to keep them strong. Low rates of calcium intake tend to be highly correlated with low bone mass and elevated bone fracture rates. This mineral is also needed to help teeth develop fully and then to protect them from decay. About 99% of all the calcium in the human body is present in the bones and teeth. The remaining portion is found in tissues and fluids, including the blood. The calcium present in these parts of the body has the following functions:

  • Aids in regulating heartbeat
  • Conducts nerve impulses that send messages through the central nervous system
  • Helps blood vessel and muscle contraction and expansion
  • Lowers blood pressure
  • Regulates fluid balance by controlling the flow of water into and out of the cells
  • Stimulates enzyme and hormone secretion
  • Triggers the formation of blood clots

Some studies indicate that increased consumption of calcium may lower the risk of colorectal cancer but other studies suggest that it may actually increase the risk of prostate cancer. Furthermore, one recent observational study published in the journal Heart found that consumption of calcium supplements nearly doubles the risk of heart attack. Hence, not all of the aforementioned health benefits of calcium are without controversy.

Calcium Deficiency

Calcium deficiency simply means that people have inadequate stores of calcium. This can result from poor diet, decreased calcium absorption or increased calcium excretion. The body’s calcium stores are constantly being depleted through shed hair, skin, nails, sweat, feces and urine. Moreover, calcium can only be absorbed in the digestive tract if the body also has an adequate supply of vitamin D.

When calcium levels in the body fall too low, the bones have to supply calcium to tissues and fluids so that normal biological functions can continue. As a result, calcium deficiency can cause the bones to weaken, raising the risk of fracture and increasing the risk of osteoporosis. A person will typically not experience any symptoms of calcium deficiency while the body will be depleting the calcium stores in the bones. Low blood calcium known as hypocalcemia is usually not caused by a lack of dietary calcium but is a result of other medical conditions or use of medications. In extreme cases, hypocalcemia can cause abnormal heart rhythms and may even be fatal.

Dietary Sources of Calcium

Depending on the culture, the biggest sources of calcium include milk and dairy products, fish with bones and soy and soy products. Other good dietary sources of calcium include almonds, orange juice, dried figs, green leafy vegetables, fortified cereals and some dried beans. Remember that vitamin D is vital for the body to process calcium, so make sure you also get adequate amounts of this vitamin from your diet. Experts generally recommend that people, especially children, get their calcium from dietary sources but in some cases a doctor may recommend supplementation.

Potential Interactions of Calcium Supplements with other Substances

Some medications may interact poorly with calcium supplements, including:

  • Aluminum or magnesium containing antacids
  • Antibiotics such as fluoroquinolone or tetracycline
  • Anticonvulsants such as phenytoin
  • Anti-inflammatory drugs such as glucocorticoids
  • Diuretics such as thiazide
  • Drugs used to treat thyroid condition such as levothyroxine
  • Heart medications such as Digoxin
  • Mineral oil or stimulant laxatives