Calcium keeps your bones and teeth strong, where 99 percent of your body's total calcium stores are concentrated. Your body uses the remaining 1 percent for normal artery function, muscle health, nerve signaling and hormone secretion. Ideally, you will meet your calcium needs through your diet. But sometimes this is difficult, and taking a supplement can prevent a deficiency. Even though dietary calcium may pose some health risks, most stem from taking too much supplemental calcium.
Maximum Intake
Total calcium intake, including supplements and diet, should not exceed 2,500 mg, according to the National Institutes of Health Office of Dietary Supplements. Regularly consuming more on a prolonged basis will increase the risk of side effects. Since this upper limit applies to total calcium intake and not just supplements, it is important to ask your doctor about the proper dosage for your condition. Most doctors recommend adults take between 800 mg and 1,000 mg of supplemental calcium, according to the University of Michigan Health System.
Increased Risk of Kidney Stones
Calcium forms a major component of most kidney stones, and using calcium supplements might increase the risk of developing them. University of Maryland Medical Center notes that calcium from the diet does not appear to pose a similar risk. If you have a history of kidney stones, talk to your doctor before using supplements and aim to get the bulk of your calcium through the diet.
Increased Risk of Prostate Cancer
Some concern exists over high calcium intake and an increased risk of prostate cancer. The National Cancer Institute reports on two large studies that found high intake of dietary calcium, particularly low-fat dairy, was associated with an increased risk. Supplements and calcium from nondairy sources did not appear to influence cancer development. It also reports that other studies have not found an increased risk of prostate cancer from consuming calcium in any form, however. The true effects of calcium on prostate health remain unclear, but if you have a risk of developing this cancer, talk to your doctor about appropriate calcium intake.
Organ and Tissue Damage
Taking too much calcium can lead to calcification, or hard calcium deposits, in the soft tissues and arteries. Rarely, it might cause kidney damage. This seems to result from very high doses, however -- 5 g daily or 3 g if you already have kidney disease, according to the National Cancer Institute. If you have kidney disease, talk to your doctor before using calcium in any dose.
Phosphorus Imbalance
Phosphorus and calcium work together to keep bones strong. High levels of one and low levels of the other can affect this relationship and compromise bone health. The University of Michigan Health System reports on research which found calcium supplements reduced phosphorus levels. The typical Western diet usually provides ample, if not excess levels of phosphorus, which would prevent this problem in most instances. It notes that older individuals, however, might be vulnerable to this effect and recommends taking a calcium supplement that contains phosphorus.
Medication Interactions
Medications such as digoxin, thiazide diuretics and those used in estrogen therapies increase calcium levels in the blood; taking calcium supplements might increase it further to dangerous levels. Calcium supplements might decrease the effectiveness of osteoporosis medicines, quinolone antibiotics and tetracycline antibiotics. The University of Maryland Medical Center recommends taking calcium supplements at least two to four hours before or after these drugs.
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