The Chemistry of Calcium and its Relation to Biological Function

Calcium is the most abundant mineral in the human body. Considering our bones and teeth are mostly comprised of calcium, that isn’t hard to imagine. Of all the calcium in the human body, 99% of it is contained in the bones and teeth. The remaining 1% is found throughout the body in blood, muscle, and in the fluid between cells.

The non-skeletal calcium plays several vital roles biological functions in the human body: it is needed for muscle contraction, blood vessel contraction and expansion, the secretion of hormones, and for the process of sending messages through the nervous system. Because these functions are so vital, the body maintains a constant level of this fluid based calcium by taking calcium from the bones when needed.


The bones need to undergo continuous remodeling to keep proper levels of calcium in the blood. Bone is a living tissue, and it continues to change throughout your life. For the first thirty years of life, bones continue to grow and become more dense. Later in life, there is a gradual decrease in bone density as the calcium is used up for the other body functions. Younger people can absorb calcium more readily; infants can have an absorption rate of around 60%, whereas older people may only absorb 10-15% of the calcium they consume. This is the reason many older people develop osteoporosis.

To keep bones healthy, you must do two things: absorb adequate amounts of calcium and vitamin D (vitamin D is needed for the body to process the calcium absorption), and engage in weight bearing exercise (this increases bone strength and density).


Some studies have shown that a high intake of calcium may reduce blood pressure and thereby reduce the risk of hypertension. The results of most studies, however, produced small and inconsistent results. Part of the reason for the inconsistencies may be because the research tends to look at the effects of just one nutrient instead of considering a full dietary change.

One project that did look at the effect of overall dietary changes to reduce blood pressure was the DASH diet (Dietary Approach to Stop Hypertension). This study does suggest a strong correlation between calcium intake and lowering blood pressure.


The correlation of calcium intake and cancer is an even murkier subject. Some studies indicate that higher calcium intake may reduce the likelihood of developing colorectal cancer. Other studies show that higher calcium intake may INCREASE the risk of prostate cancer.

Studies on both forms of cancer as related to calcium intake are still inconclusive at this time. To date, there have been no large clinical trial; most of the trials have been experimental or observational in nature. Don’t spend time fretting over the possible increased risk of colon cancer as the known benefits of calcium are overwhelming.


Kidney stones, a painful and potentially dangerous condition, are crystallized deposits of calcium and other minerals in the urinary tract. Previously, a high calcium intake or absorption rate were thought to contribute to the development of kidney stones. More recent studies show that high dietary calcium intakes actually decrease the risk for kidney stones. Other factors, such reduced fluid consumption, appear to be greater contributors to the risk of forming kidney stones.


The Office of Dietary Supplements (ODS) at the National Institute of Health Website:
(Includes RDA charts, calcium related health risks, and food source charts)

National Heart, Blood and Lung Website:
(Information on the DASH diet for lowering blood pressure)