Intake of vitamins B6 and C and the risk of kidney stones in women
Curhan, G. C., Willett, W. C., Speizer, F. E., Stampfer, M. J.
J Am Soc Nephrol 10:4:840-845, Apr 1999

Abstract

Urinary oxalate is an important determinant of calcium oxalate kidney stone formation. High doses of vitamin B6 may decrease oxalate production, whereas vitamin C can be metabolized to oxalate. This study was conducted to examine the association between the intakes of vitamins B6 and C and risk of kidney stone formation in women. The relation between the intake of vitamins B6 and C and the risk of symptomatic kidney stones were prospectively studied in a cohort of 85,557 women with no history of kidney stones. Semiquantitative food-frequency questionnaires were used to assess vitamin consumption from both foods and supplements. A total of 1078 incident cases of kidney stones was documented during the 14-yr follow-up period. A high intake of vitamin B6 was inversely associated with risk of stone formation. After adjusting for other dietary factors, the relative risk of incident stone formation for women in the highest category of B6 intake (> or =40 mg/d) compared with the lowest category (<3 mg/d) was 0.66 (95% confidence interval, 0.44 to 0.98). In contrast, vitamin C intake was not associated with risk. The multivariate relative risk for women in the highest category of vitamin C intake (> or =1500 mg/d) compared with the lowest category (<250 mg/d) was 1.06 (95% confidence interval, 0.69 to 1.64). Large doses of vitamin B6 may reduce the risk of kidney stone formation in women. Routine restriction of vitamin C to prevent stone formation appears unwarranted.

Linus Pauling was a mentor of mine and a sponsor of the Center for Vitamins and Cancer Research that I co-founded at the University of Colorado Medical School in 1980. He was a great supporter of Vitamin C for all that ails you. There are many recent research papers showing reduction in heart disease, increased longevity, and so forth from taking more than 10 times the government recommended amount of Vitamin C. One of the arguments against taking large amount of Vitamin C was the risk of kidney stones. That debate has been laid to rest by a large study showing no increase in kidney stones from Vitamin C and a significant reduction in kidney stones from increased Vitamin B6.

The above originally posted by Jeff Sutherland

Why Don't Massive Doses of Ascorbate Produce Kidney Stones?

Years ago when Linus Pauling wrote his book "Vitamin C and the Common Cold", the critics immediately labeled the taking of large doses of vitamin C dangerous because it would produce calcium oxalate kidney stones. This practice of telling people that vitamin C caused kidney stones continues today by the critics of vitamin C despite the lack of clinical evidence of kidney stones in people taking vitamin C

It was hypothesized that since a significant percentage of ascorbate was metabolized into and excreted as oxalic acid that this oxalic acid should combine with calcium in the urine and deposit as calcium oxalate kidney stones. It is true that those of us who take large doses of ascorbate have elevated oxalic acid in our urine but no kidney stones. With the millions of people in the world taking vitamin C, if vitamin C caused kidney stones there would have been a massive epidemic of kidney stones noticed by this time. There has been none.

I started using vitamin C in massive doses in-patients in 1969. By the time I read that ascorbate should cause kidney stones, I had clinical evidence that it did not cause kidney stones, so I continued prescribing massive doses to patients. To this day I estimate that I have put 25,000 patients on massive doses of vitamin C and none have developed kidney stones. Two patients who had dropped their doses to 500 mg a day developed calcium oxalate kidney stones. I raised their doses back up to the more massive doses and added magnesium and B6 to their program and no more kidney stones. I think that the low doses had no effect and they, by coincidence, developed the kidney stones because they were not taking enough vitamin C.

The question remains, however, why do not people taking large doses of ascorbate develop kidney stones. I had in 1985 hypothesized that one of the reasons that we did not develop kidney stones was that the ascorbate excreted in the urine sterilizes the urine and "should prevent many of the niduses of infection around which oxalate stones frequently form." (Cathcart, RF. Vitamin C: the Nontoxic, Nonrate-Limited, Antioxidant Free Radical Scavenger. Medical Hypotheses, 18:61-77, 1985.)

In an article in ScienceNewsOnline, August 1, 1998, the Bacteria in the Stone it is said that Extra-tiny microorganisms may lead to kidney stones and other diseases. Tiny nanobacteria, as small as the larger viruses, live in urine and, by precipitating calcium and other minerals around themselves, induce the formation of kidney stones. It seems that the large doses of ascorbate by causing the excretion of ascorbate in the urine probably kills the nanobacteria and prevents the formation of stones.

In addition, the massive doses of ascorbate assist the immune system to kill bacteria within the body but have the ability to kill bacteria by some mechanism, which does not seem to involve the immune system. These bacteria and L-forms of bacteria hide out in cells especially when antibiotics are used and explain some of the resistance acquired by bacteria against antibiotics. I have yet to see bacteria that can become resistant to massive doses of ascorbate in combination with first and second-generation antibiotics. Admittedly in a private practice, I do not see the most resistant bacteria but this combination has been impressive and deserves to be tried against the most resistant bacteria. It may solve the impending problem of increasingly resistant bacteria.

See also the med center study indicating that even moderate doses of C prevent kidney stones.

A prospective study of the intake of vitamins C and B6, and the risk of kidney stones in men.

Curhan GC, Willett WC, Rimm EB, Stampfer MJ.

Department of Epidemiology, Harvard School of Public Health, Boston, Massachusetts 02115, USA.

PURPOSE: The association between the intake of vitamins C and B6, and kidney stone formation was examined. MATERIALS AND METHODS: 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. Vitamin intake from foods and supplements was assessed using a semiquantitative food frequency questionnaire completed in 1986. RESULTS: During 6 years of followup 751 incident cases of kidney stones were documented. Neither vitamin C nor vitamin B6 intake was significantly associated with the risk of stone formation. 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 (95% confidence interval 0.54 to 1.11). For vitamin B6 the age-adjusted relative risk for men consuming 40 mg. daily or more compared to less than 3 mg. daily was 0.91 (95% confidence interval 0.64 to 1.31). After adjusting for other potential stone risk factors the relative risks did not change significantly. CONCLUSIONS: These data do not support an association between a high daily intake of vitamin C or vitamin B6 and the risk of stone formation, even when consumed in large doses.

PMID: 8618271 [PubMed - indexed for MEDLINE]