Calcium’s major role is to help bones grow and to keep them strong. Numerous studies show that low rates of calcium intake are highly correlated with low bone mass and bone fracture rates. Calcium is also necessary to help baby teeth and adult teeth develop fully. After teeth have developed, calcium may help protect them from decay. About 99 percent of all the calcium in the body is found in the bones and teeth.

Calcium also is found in tissues, the blood and other fluids. The calcium found in these parts of the body has several roles, including:

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

Recent studies also appear to show that increased consumption of calcium lowers blood pressure. Studies have been inconclusive regarding whether or not increased calcium intake lowers the risk of colorectal and prostate cancer.

One recent study found that mothers who increase their intake of dietary calcium during pregnancy are more likely to give birth to babies with stronger bones and higher birth weights. Another recent study found that women who do not have enough calcium in their diets when breastfeeding risk bone loss around the teeth and gums.

When people do not have adequate stores of calcium, the condition is known as a calcium deficiency. This can result from inadequate calcium intake, decreased calcium absorption and increased calcium excretion.

People must get adequate levels of calcium from their diet every day because the body does not make this mineral. In addition, the body’s calcium stores are constantly being depleted through shed skin, nails, hair, sweat, urine and feces. In addition, calcium can only be absorbed in the digestive tract under certain conditions. A protein produced by vitamin D helps the body absorb calcium. Thus, if the body does not have adequate amounts of vitamin D, it cannot absorb calcium.

When calcium levels in the body fall too low, the body begins to break down bone to obtain calcium so that normal biological functions (e.g., nerve and muscle function) can continue.

Calcium deficiency can cause the bones to weaken, raising the risk of fracture. Long-term calcium deficiency also increases the risk of a thinning of the bones known as osteoporosis. This disease affects 10 million Americans, 80 percent of whom are women, according to the National Institutes of Health (NIH). Another 34 million Americans have low bone mass (osteopenia), a condition that precedes osteoporosis. Although osteoporosis is much more common in women, it also can affect men. In fact, after age 65, the rate of bone loss in men is the same as in women. One-third of men who are at least age 75 have osteoporosis.