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Roles of Vitamin D for Calcium Absorption in Our Body Digestive System

Updated on July 6, 2011

Calcium Absorption

Calcium absorption is an important aspect of calcium nutrition for human health. It is the process in which calcium contained in foods (natural or supplement) you consume is transferred from digestive system into the body for use. The site of calcium absorption in digestive system is the small intestine. You have to be aware that not all the calcium you take in foods is absorbed without loss. It is a normal condition that only about 40 percent of the calcium you consume is absorbed into the blood stream. The rest of the calcium is lost in the feses and thus nt available for use in the body.

When you are taking a calcium supplement to meet your calcium needs, make sure that you know how much elemental calcium the suplement contains. You can then predict how much of that elemental calcium will be absorbed and available for use in your body metabolism. These 2 basic information will help you decide how much and which supplement you are going to take to satisfy your calcium requirement.

Calcium absorption is affected by many factor, and one of which is Vitamin D. What have Vitamin D got to do in calcium absorption?

Roles of Vitamin D in Calcium Absorption

Calcium and Vitamin D work together as a team in creating a healthy human. When talking about calcium, do not forget about Vitamin D. Failure to do this may lead you to get incomplete and misleading information about calcium. For example, ostoporosis is indeed a disease caused by calcium deficiency, but there are osteoporosis cases which are due to Vitamin D deficiency.

Vitamin D is very important for calcium to get absorbed from the small intestine. The way Vitamin D acts in assisting calcium is through a hormone called parathyroid which is secreted by parathyroid glands. Whenever circulating concentration of calcium in blood serum becomes too low, for example during low calcium intakes and absorption, the parathyroid hormone released from the parathyroid glands stimulates the activity of an enzyme in the kidney. This enzyme is responsible for the production calcitriol, the biologically active form of vitamin D3. The hormone tells the enzyme to produce more of the calcitriol in response to lowered concentration of calcium in blood serum. Increased production of calcitriol will bring calcium concentration back to normal in one or more of the following ways:

  1. by activating the Vitamin D-dependent absoption system in the small intestine, so that increasing the absorption of dietary calcium;
  2. by increasing the mobilization of calcium from bone into the circulation
  3. by increasing the reabsorption of calcium by the kidneys.


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