Calcium supplements – helpful or harmful?
The need for calcium, especially in women over age 50, isn’t exactly news. But reports of a possible link between calcium supplementation and increased cardiovascular events, constipation and kidney stones have surfaced over the last decade (Downing and Ilam, 2013). Given the need for calcium and the difficulty getting enough through the diet makes this a potential crisis. People die from cardiovascular events but they also die from fractures caused by osteoporosis. Is there a way to meet the need for calcium without increasing the chances of other developing other diseases?
When bones are too thin, the individual is diagnosed with osteoporosis (literally porous bones). The major complications with that disease is fractures and a fracture can easily lead to other problems such as blood clots and skin sores from immobility.
In women over age 50, the rate of bone destruction is usually greater than the rate of bone building. On average, they lose about 1% of their bone every year. It doesn’t take much calculating to appreciate the effects of such bone thinning in older women. The same loss occurs in older men but males have thicker bones and the accelerated bone loss tends to start much later in life. A diet high in calcium from dairy products, sardines, oatmeal and leafy green vegetables or regular calcium supplementation both lead to an increase in bone mineral density but not many people consume enough dietary calcium (AFP, 2016).
A high blood calcium level is associated with thicker carotid artery plaque and that correlates with an increased stroke risk. Arterial plaque calcification is also associated with increased cardiovascular disease and death. Excess calcium doses appear to interfere with normal calcium regulation and allows excess calcium into tissues. That may destabilize arterial plaque and lead to a heart attack or stroke (Downing, L., 2013). In addition, it was reported in the December 2015 issue of Urology Times that those with a history of kidney stones form new stones more quickly and at a higher rate if they’re taking calcium supplements (Urology Times).
The key to solving this dilemma lies in the amount of calcium supplementation. Taking more than 3 grams (3,000 mg.) a day of calcium tablets is associated with hypercalcemia, especially if taken with vitamin D because that increases absorption. Hypercalcemia is associated with an increased risk of kidney stones, constipation, lethargy, depression and arrhythmias (Burcham, J., and Rosenthal, L, 2016). Also, in an article that summarized data from multiple studies on calcium supplementation, no association between moderate calcium supplementation and adverse cardiovascular outcomes was uncovered in healthy people (Downing, L., 2013).
It is also critical to take calcium supplements properly. Calcium tablets with more than 250 mg. of the element competes with magnesium absorption, and if calcium intake is greater than magnesium intake, arterial calcification is more likely. Such deposition of calcium in arteries is associated with an increased cardiovascular disease risk. Taking calcium tablets with an equivalent amount of magnesium is recommended. It is best to take it with food and in smaller amounts two or three times a day. Also, it should not be taken with iron or zinc.
Glucocorticoids like prednisone decrease calcium absorption, as does insoluble fiber, phytic acid (in whole grain cereal and wheat bran), and oxalates (in spinach, rhubarb, beets and Swiss chard). Loop diuretics like furosemide (Lasix) increase the excretion of calcium but thiazide diuretics like hydrochlorothiazide (HCTZ) decrease the loss of calcium into the urine. Conversely, calcium can decrease the absorption of some medications including tetracycline and fluoroquinolone antibiotics, thyroid hormone (levothyroxine), phenytoin and the bisphosphonates (drugs like alendronate used for osteoporosis treatment).
Finally, it should be noted that several hours of weight-bearing exercise per week, such as walking or dancing, provides the mechanical stress to increase bone formation, a phenomenon that strengthens bones in a way that is separate from the calcification of bone tissue. Calcium supplementation can help keep bones strong even in postmenopausal women, but excess doses and other pitfalls need to be considered and avoided to keep supplementation a positive thing. This article is not intended to replace the medical care provided by your health care provider, but instead to make you more aware of important information and prompt you to discuss it with your health care provider.
American Family Physician Audio Digest for October, 2016
Burcham, J., and Rosenthal, L. Lehne’s Pharmacology for Nursing Care, 9th edition. St. Louis, MO: Elsevier, 2016.
Downing, L, and Ilam, M. Influence of Calcium supplements on the occurrence of cardiovascular events. American Journal of Health-Systems Pharmacy, vol. 70, July, 2013.
Turner, L. Perfect Timing: When and how you take your supplements may be as important as what you take. Better Nutrition, February, 2018.
Calcium supplements may heighten risk of kidney stone recurrence. Urology Times, December, 2015.