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The Nutrition InvestigatorThe health and nutrition blog by Dr. Roc Ordman.

Kidney Stones

by Roc (click here for full post)

Although many urologists believe that kidney stones are caused by vitamin C supplements, this is because many stones are made of oxalic acid, and vitamin C, ascorbic acid, can be metabolically transformed into oxalic acid. However, all of the peer-reviewed published evidence as of 2011 indicates that taking vitamin C supplements does not increase the risk of kidney stones, and is likely to reduce the risk by creating acidic urine that dissolves stones. For an excellent review, see the Linus Pauling Institute essay. – http://lpi.oregonstate.edu/f-w99/kidneystones.html

Please help educate physicians, esp. urologists, by bringing them articles from AJCN and J. Nutrition to help them learn that vitamin C probably prevents, and does not cause, kidney stones. They are very unpleasant, and expensive to treat if allowed to develop.

You can also find numerous articles from the current literature summarized at my website by clicking on the search button at the upper left of this page, and searching for kidney stone. That takes you here: http://chemistry.beloit.edu/Ordman/nutrition/corzoogle.php?q=kidney+stone.

Here’s the summary of what I found there – articles about vitamin C and kidney stones, and about other nutrition likely to contribute to stones, with peer-reviewed references. I note that I never had a kidney stone until I stopped taking 500 mg of vitamin C twice a day. And so I restarted, and the stone went away.

REFERENCE: American Journal of Clinical Nutrition, Vol. 81, No. 4, 736-745, April 2005, Vitamins E and C are safe across a broad range of intakes – “Some case reports suggest that unusually high intakes of vitamin C, especially in persons who are given the vitamin intravenously or who have chronic renal failure, may be associated with the development of oxalate kidney stones (81). However, it is uncertain whether this risk occurs in the general population (78).

* 78. Rivers JM. Safety of high-level vitamin C ingestion. Int J Vitam Nutr Res Suppl 1989;30:95–102.[Medline]
* 81. Curhan GC, Willett WC, Rimm EB, et al. A prospective study of the intake of vitamins C and B6 and the risk of kidney stones in men. J Urol 1996;155:1847–51.[Medline]

REFERENCE: The 1,000 mg dosage is the lowest to show significantly elevated levels of oxalic acid in the urine, which Levine states might increase the risk of kidney stones. However, the slight acidification of the urine could also have benefits, and the study of Stampfer (4) has shown that those taking elevated doses of vitamin C in fact have a 22% lower incidence of kidney stones.

(4) Curhan, GC, Willett, WC, Rimm, EB, and Stampfer, MJ, “A prospective study of the intake of vitamins C and B6, and the risk of kidney stones in men”, J Urol 155: 1847-51 (1996) “We conducted a prospective study of the relationship between the intake of vitamins C and B6 and the risk of symptomatic kidney stones in a cohort of 45,251 men 40 to 75 years old with no history of kidney calculi…For vitamin C the age-adjusted relative risk for men consuming 1,500 mg daily or more compared to less than 250 mg daily was 0.78…After adjusting for other potential stone risk factors the relative risks did not change significantly.”

REFERENCE: Rivers, Jerry M. “Safety of High-level vitamin C Ingestion”, pp. 445-454. No danger of oxalate stones or iron overload. “large doses [above 5 g] should not result in increased oxalate formation since the metabolic turnover of the vitamin is limited”

REFERENCE: Susan A. Kynast-Gales et al, Ascorbate Increases Human Oxaluria and Kidney Stone Risk, J. Nutr. 2005 135: 1673-1677

Vitamin C supplements are taken by 12.4% of US adults. 12-14% of people getting kidney stones report taking more than 500 mg of vitamin C per day. (SO KIDNEY STONES ARE NO MORE COMMON IN PEOPLE WHO TAKE VITAMIN C THAN IN THE REST OF THE POPULATION. TAKING VITAMIN C AND KIDNEY STONES HAVE NO CORRELATION.) This article provides kinetics of vitamin C [ascorbic acid, AA] metabolism when 1000 mg of AA is taken twice a day. “Although urinary oxalate was shown to increase with [AA of 1,000 mg twice a day], a direct association of AA supplementation with stone incidence is not clear.”

OTHER THINGS TO NOTE:

* Phosphoric acid from soda pop is linked to kidney stones

* High protein in the diet favors kidney stones

*litnotes AJCNMay08 turmeric may contribute to kidney stones

*AJCN March, 2010 Low salt diet reduces loss of calcium and formation of kidney stone

* Calcium SUPPLEMENTS increase the risk of kidney stones in postmenopausal women. Dietary calcium sources like cheese do not.

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