Calcium is an abundant mineral found in foods and available as a dietary supplement. It is required for muscle function, nerve transmission and hormone secretion, according to the Office of Dietary Supplements at the National Institutes Of Health. The amount of calcium in your body is tightly regulated by bodily functions and does not fluctuate with changes in your dietary intake. This means that the amount of calcium in the blood does not usually change if you take a calcium supplement or eat foods high in calcium. However, calcium is stored in bone and tissue and used to maintain that constant blood concentration.
Sources
Calcium is found naturally in dairy products such as milk, yogurt and cheese as well as other sources, including vegetables such as kale, broccoli and Chinese cabbage. Some foods are also fortified with calcium. According to the Office of Dietary Supplements, two main forms of supplements are calcium carbonate and calcium citrate. Calcium carbonate is less expensive and more convenient. Scientists think that both are similarly absorbed.
Calcium Pump
Every time your muscles contract and relax it requires the combined action of minerals, membranes and myosins. When the nerve signals a muscle cell to contract, the cell releases calcium from within the cell that rapidly spreads and acts on myosin protein. This shifts the shape of the myosin and allows it to bind, which then contracts muscle until the calcium is removed, according to Research Collaboratory for Structural Bioinformatics Protein Data Bank. This action of calcium allows the muscle to relax after contraction, when the calcium is removed. Powered by adenosine triphosphate, the calcium pump brings the calcium ions back into the cell and reduces the level around the myosin, which helps control muscle contraction and relaxation.
Role of Calcium in the Heart
The calcium release, contraction and relaxation of muscle in the heart and skeletal system are similar but not identical, according to Dr. S. Fleischer from the Department of Molecular Biology at Vanderbilt University. The heart uses two sources of calcium as opposed to the single source by the skeletal muscle, and the calcium released in the heart is more sensitive. Identifying this channel of calcium release has been a significant breakthrough in research and helps to define the precise method of contraction and therefore drives research and development of medications that can help to improve heart muscle contractility. According to Dr. Andrew Marks from Columbia University, heart muscle contractility is dependent upon calcium and its release from within the heart muscle cells. This intricate pathway is under further investigation to find other calcium dependent protein molecules that may be important contributors to heart failure and thus improve our understanding of the condition, increasing the potential for improved treatments.
Calcium Supplements and Heart Attack Risk
In August 2010 Dr. Marc Bolland from the University of Auckland, New Zealand, published a study in the "British Medical Journal" describing the use of calcium supplements without vitamin D, which was associated with an increased risk of myocardial infarction. Previous studies revealed conflicting results about the use of calcium supplementation. Researchers looked at randomized trials of calcium supplementation of at least 500 mg per day that lasted for at least a year and had at least 100 participants in the study who were age 40 and older. They found that calcium supplementation was associated with a 30 percent increase in the incidence of a heart attack and tended to be greater in those studies where individuals took higher doses of calcium. Researchers recommended that patients should discuss options for calcium supplementation with their physicians prior to initiating supplementation on their own.
References
- Office of Dietary Supplements at the National Institutes Of Health: Calcium
- Research Collaboratory for Structural Bioinformatics Protein Data Bank:The Calcium Pump
- Progress in Clinical and Biological Research; "Regulation of Muscle Contraction and Relaxation in Heart"; S. Fleischer; 1988
- The Journal of Clinical Investigation; "Calcium and the Heart: A Question of Life and Death"; Marks, A; March 2003
- TheHeart.org; "Calcium Supplements Boost Heart-Attack Risk: Meta-Analysis"; Fran Lowry; August 2010
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