Constipation, bloating, and gas are sometimes reported with the use of calcium supplements.353 A very high intake of calcium from dairy products combined with large amounts of supplemental calcium carbonate (used as an antacid) was reported in the past to cause a condition called “milk alkali syndrome.” This toxicity is rarely reported today because most medical doctors no longer tell people with ulcers to use this approach as treatment for their condition.
People with hyperparathyroidism, chronic kidney disease, or kidney stones should not supplement with calcium without consulting a physician. For other adults, the highest amount typically suggested by doctors (1,200 mg per day) typically does not cause side effects. People with prostate cancer should avoid supplementing with calcium without medical supervision.
A combined analysis of 15 controlled trials found that long-term calcium supplementation was associated with a significant increase of approximately 30% in the incidence of myocardial infarctions (heart attacks).354 Since these studies were not designed to examine the effect of calcium on heart attack risk, it is possible that the findings in this post hoc (after the fact) analysis were due to chance. A more recent study found that long-term calcium supplementation did not result in an increased incidence of cardiovascular disease-related death or hospitalization.355 Moreover, a pooled analysis of randomized controlled trials found that supplementing elderly individuals with a combination of calcium and vitamin D significantly decreased the mortality rate by 7%.356
In the past, calcium supplements in the forms of bone meal (including microcrystalline hydroxyapatite [MCHC]), dolomite, and oyster shell have sometimes had higher lead levels than permitted by stringent California regulations, though generally less than the levels set by the federal government.357 “Refined” forms (which would include calcium citrate malate [CCM], calcium citrate, and most calcium carbonate) have low levels of lead.358 More recently, a survey of over-the-counter calcium supplements found low or undetectable levels of lead in most products,359 representing a sharp decline in lead content of calcium supplements since 1993. People who decide to take bone meal, dolomite, oyster shell, or coral calcium for long periods of time can contact the supplying supplement company to request independent laboratory analysis showing minimal lead levels.
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The information presented in Aisle7 is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. Self-treatment is not recommended for life-threatening conditions that require medical treatment under a doctor's care. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires June 2015.