Calcium is one of the major building blocks of the human body and other living organisms. An essential element in cellular movement, calcium acts as a messenger and controls a variety of cellular reactions. It is needed for the proper functioning of the nervous system, heart and the bones.
The human skeleton houses 99 percent of the calcium in the body. The bones act as a calcium reservoir and help maintain the levels of calcium in the blood stream, which is vital in muscle contractions, maintaining healthy nerves and the timely release of hormones. When people lack calcium in the bloodstream, the body automatically takes the necessary calcium crystals from the bones, which can lead to weaker and denser bones.
While it is important to take in calcium, the rate of calcium absorption is also critical. For humans, how well the body absorbs calcium depends on a person's age, the presence or absence of other nutrients and even on a person's lifestyle. As people age, their ability to absorb calcium is greatly reduced, which often results in higher fracture rates and the occurrence of osteoporosis in women. The body also needs vitamin D to increase calcium absorption from the intestine. Excessive drinking of alcohol and caffeine, as well as consuming food high in animal protein, also reduces the body's ability to process calcium.