Dolomite is a balanced source of calcium and magnesium. Why is it not commonly offered as a nutritional supplement?

— Just wondering

Dear Just wondering,

Dolomite, or calcium magnesium carbonate, is a common mineral extract that occurs as crystals in large rock beds of limestone. Calcium carbonate is a cheap calcium supplement with a high percentage of calcium by weight, but the body has difficulty in breaking it down for use. Though dolomite in powdered form is soluble in weak acids, stomach acid doesn’t do the best job of dissolving it, especially in people with decreased stomach acid secretions (e.g., sick and elderly people). Other forms of calcium like calcium citrate are easier for the body to absorb.

In addition to being a less effective source of calcium, dolomite may be hazardous to your health. Dolomite deposits also contain other elements such as barium, lead, and iron and manganese carbonates as impurities. In the early 1980s, concern arose regarding heavy-metal contamination of calcium supplements when a study found high concentrations of lead in dolomite supplements. Since it may contain the toxic elements mercury and lead, dolomite is not a recommended source for calcium and magnesium — other forms of these minerals are available that would be safer to take.

See Iron, calcium, and constipation, oh my! for more info about calcium supplements. If you have questions about your individual nutritional needs or want more advice on nutritional supplements, talk with a health care provider or registered dietitian.


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