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Vitamin C and Kidney Stones

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Vitamin C is ascorbic acid. Some take extra vitamin c to prevent and treat colds. Others take it for other reasons.

But…If you’ve ever had a kidney stone – you may want to skip extra supplements of Vitamin C altogether.

A new study in the Journal of the American Medical Association which followed more than 22,000 men for more than 10 years finds those who took high doses of vitamin c supplements doubled their risk of getting a kidney stone.

The increased risk was seen only in those taking extra doses of vitamin C and not in those just taking a multivitamin.

How much C is too much- is not exactly clear. But this study was done in Sweden where most vitamin c supplements contain 1000 mg per tablet. The kidney stone risk was highest in those taking more than 7 vitamin c supplements a week.

Why the increased risk?

Kidney stones are often composed of calcium and oxalate. When excess vitamin c is excreted by the body- it’s usually in the oxalate form- and this may lead to more stones.

The caution applies only to vitamin c supplements and not to vitamin c found in foods. No link to stones was found for foods high in C.

This study was done in men- who happen to be more likely than women to develop stones. But having had a kidney stone myself, I can tell you, it’s not what you want .

To help prevent kidney stones, make sure you stay hydrated, which can be especially challenging when exercising in hot weather, and skip the C.