How to ensure adequate intake of calcium?
Low-fat dairy products are the best sources of calcium. Calcium supplements should be added when the desired goal cannot be reached with dietary sources alone. Calcium carbonate and calcium citrate are both well absorbed when taken with meals. Gastric acid is needed for normal calcium absorption; calcium carbonate absorption may be significantly reduced in patients who have achlorhydria or who use a proton pump inhibitor (PPI). Calcium citrate absorption is less likely to be affected by PPI use. Calcium citrate is also a better choice in patients with a history of kidney stones since citric acid is often low in the urine of stone formers. Total calcium intake (dietary + supplements) should not exceed 2000 mg/day chronically.
Note: the addition of magnesium, boron, and vitamin K does not increase the effectiveness of calcium supplementation but does add to cost. Patients on warfarin should be warned to avoid calcium preparations that contain vitamin K (e.g., viactiv). Patients who experience constipation with calcium supplements may benefit from formulations that contain magnesium.