Myth Busting: Vitamin C causes kidney stones?
It’s odd how many medical writers seem eager to find reason to believe vitamin C is somehow dangerous. Many occurring articles tell of how vitamin C causes kidney stones. These reports fail to give conclusive evidence of both the increase or size of the stones. These “scare reports” rely much on ambiguous indicators of unlikely risk.
No proof exists to uphold the idea that vitamin C causes kidney stones, but rather evidence proves that high doses may cure such problems. A study analyzed 85,557 women over the course of 14 years, finding no evidence to believe vitamin C is the culprit from kidney stones. The subjects supplementing 250mg per day and those taking at least 1.5grams had no differences in occurrences in stones. The study performed was a follow up of one earlier done on 45,251 males. The study of men concluded that doses of vitamin C of at least 1.5 grams lessened the risk of kidney stone formation.(1)
Vitamin C increases the amount of oxalate and urate in the body which can accumulate in kidney stones. Given this, many health authors believe vitamin C will elevate chances of forming stones. However, this has never been confirmed. If research stopped here, it would these authors better reason to believe this, but vitamin plays an important role in reversing the environmental conditions for kidney stones.
Almost 75% of kidneys stones are formed of calcium oxalate. Although vitamin C increases excretion of oxalate in the system, it has characteristics that may have reverse effects. Vitamin C binds to calcium; this lowers the possibility of calcium oxalate formation. It also has diuretic abilities, which create an unlikely environment for kidney stones. Lastly, kidney stone formations lean more towards areas of infections. High doses of Vitamin C are bactericidal (it kills bacteria) and may remove bacteria that stones form around.
This evidence suggests that supplementing large doses of Vitamin C has no effect on the formation of kidney stones, but rather may be curative of such problems.
(1) Curhan, G. C., Willett, W. C., Speizer, F. E., Stampfer, M. J. (1999) Megadose Vitamin C consumption does not cause kidney stones. Intake of vitamins B6 and C and the risk of kidney stones in women, J Am Soc Nephrol., Apr, 10, 4, 840-845.