Kidney Stones and Calcium

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Kidney Stones and Calcium

Kidney stones most often consist of calcium oxalate. For this reason medical wisdom has long dictated that people who are prone to developing kidney stones should limit their calcium intake. Recent studies have shown this assumption to be incorrect. Now a major study carried out at the Harvard Medical School concludes that for women to limit dietary intake of calcium is precisely the wrong thing to do to prevent kidney stones.

Dr Gary Curhan and colleagues studied over 90,000 nurses who enrolled in the Nurses' Health Study in 1980. Statistical analysis showed that women whose daily intake of calcium from dietary sources exceeded 1,100 mg had about half the risk of developing kidney stones as did women whose intake was less than about 500 mg per day.

The researchers believe that calcium reduces the absorption of oxalate from food, and that this is the main reason a high dietary calcium intake prevents stone formation.

A high intake of calcium supplements, on the other hand, seemed to increase the risk of kidney stones by 20 per cent. The researchers point out that 67 per cent of the women did not take their supplement with a meal or took it with breakfast, which usually contains very little oxalate.

They conclude that the risk of stone formation attributable to the use of calcium supplements may be reduced if the supplements are taken with meals.

Annals of Internal Medicine, April 1, 1997

Canadian Health Reform Products Ltd.

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By Hans Larsen

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