Can High Calcium Damage The Kidneys?

Calcium is the most abundant mineral in your body, and is essential for the health of your soft tissues as well as your skeleton. You may not think of calcium as a potential toxin -- toxicity from dietary calcium has never been documented -- but overconsumption of calcium supplements or disruption of your body's ability to control calcium levels can cause health problems, including serious kidney damage.

Functions

Normally, the calcium concentration in your bodily fluids is tightly regulated. If your dietary calcium intake is inadequate for supporting critical physiologic functions and maintaining a constant serum level, calcium will be leached from your skeleton at the expense of bone strength. Calcium is essential for generating nerve impulses and regulating your heartbeats and muscular contraction. Calcium also serves as a cofactor for a variety of enzymes, and is instrumental in the cell signaling processes that coordinate the activities of your tissues and organs.

Causes

Some medical conditions, such as cancer, Paget's disease or hyperparathyroidism, can cause high serum calcium levels, which is also known as hypercalcemia. "The Merck Manual of Diagnosis and Therapy" states that certain medications -- lithium, theophylline and thiazide diuretics -- have been linked to high calcium levels. Vitamin D toxicity can contribute to hypercalcemia by increasing intestinal calcium absorption. A December 2010 report in "Electrolytes and Blood Pressure" states that overconsumption of calcium supplements commonly used to treat osteoporosis can cause hypercalcemia and kidney injury.

Calcium-Alkali Syndrome

Prior to the advent of medications that inhibit stomach acid secretion, ulcers were treated with large doses of alkaline antacids and milk or cream. This sometimes led to a condition called milk-alkali syndrome, which was characterized by hypercalcemia, alterations in acid-base balance and kidney injury. With the development of newer anti-ulcer drugs, milk-alkali syndrome essentially disappeared from the scene. A similar condition, however, described in the December 2009 issue of "Internal Medicine," has re-emerged with the widespread use of calcium carbonate for treating osteoporosis. Called calcium-alkali syndrome, this condition is the second most common cause of severe hypercalcemia among hospitalized patients.

Kidney Damage

Prolonged or severe hypercalcemia -- a serum calcium level above 18 mg/dL -- can cause kidney injury. Similarly, calcium-alkali syndrome can trigger accumulation of calcium deposits in your kidneys and lead to potentially irreversible kidney damage. Calcium carbonate, a supplement commonly used to treat or prevent osteoporosis, supplies both calcium and alkali. Elderly individuals, due to their reduced kidney function, are at increased risk for calcium-alkali syndrome. In addition, vitamin D supplementation and dehydration can aggravate calcium-alkali syndrome by decreasing your ability to eliminate excess calcium.

Considerations

Hypercalcemia, whether due to excess intake or underlying medical problems, can result in kidney damage. Calcium from foods does not cause hypercalcemia, but overconsumption of calcium supplements, specifically calcium carbonate, can result in calcium-alkali syndrome. Recommended dietary intakes of calcium vary from 200 mg daily for infants to 1,300 mg for adolescents and pregnant or nursing women. If you are taking calcium supplements, follow your doctor's recommendations.