Vitamin C and kidney stones

[studentroland]

[Johnwen]

We had this subject brought up many times and it is a unproven myth.
If you go to the link it'll take you to the last thread we did on this subject.




viewtopic.php?f=3&t=10607

[majkinetor]

Weak study. Not even need to discuss it. Even if true, benefits are multiple times better then perceived risk.

My personal opinion is that if you take Mg along with C, you R safe, even if you have some form genetic risk, or kidney disfunction associated with calcium/oxalate pathways.

http://www.orthomolecular.org/resources ... 9n04.shtml
http://knowledgeofhealth.com/modern-med ... lls-again/

[studentroland]

[Dolev]

In 1996, Curhan from Harvard Med School published a very similar study and found that among 45,251 men, those who took 1500 mg or more of C compared to those taking 250 mg or less, "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." http://www.ncbi.nlm.nih.gov/pubmed/8618271

I have access only to the first page of the Swedish study, so I can't examine the data, and I have only a rudimentary knowledge of statistics, however, a couple of things I noticeds are:

1. the "sensitivity" of ascorbic acid use was only 67%, meaning that a third of the users were not identified, if I understand correctly.

2. the "specificity" was 93%, so 7% of users actually didn't use; again, I'm not sure if my understanding is correct. In any case, these figures lessen the accuracy of the results.

3. Studies based on questionnairs are not very accurate. How well do you remember what you took in the last year?

4. The headline of the article includes the words "Less is More". This shows bias in the report.

5. Out of 48,850 men, there were 436 first time cases of kidney stones, or less than 1%. I don't see the absolute risk data, but if there was a "2-fold" increase, that means that about 145 men taking vitamin C got kidney stones compared to about 290 that didn't, and that the vitamin C causes stones in about 145 men. So, about 0.3% had stones because of the vitamin, or one in 333. Pretty low risk, even if the study is completely accurate with no statistical innaccuracies, which is close to impossible.

Please point out mistakes I've made in this analysis. I'm very amatuer in statistics. I hope that Dr. Steven Hickey weighs in on this. By the way, his book, Tarnished Gold, is an absolute must for anyone who wants to not made a fool of by "evidence-based" statistical lies.

[studentroland]

[majkinetor]

[studentroland]

[VanCanada]

The study you found should have controlled for the number of people in each group who handle vitamin C differently. It's unlikely the researchers controlled for this subgroup of the population.

Check out pages 80 to 83 of "Vitamin C: How Best to Use It" by Stephen Sheffrey.

Here is an excerpt:

People who form stones regularly handle C differently. They convert most of the ingested C to oxalate in the gut, then absorb the oxalate. It's as if they were living on spinach and rhubarb. This of course leads to stones if conditions are right. If most of it converts to oxalate, do stone-formers have enough C left to keep its blood level up? No. Regular stone-formers have low C levels, either due to oxalate conversion or malabsorption. When a group of stone-formers were given 500 mg of C intravenously they failed to pass the expected amount in the urine. The body needed it, therefore refused to give it up.(Ref. 30)
-Reference 30: Chalmers A H, Cowley D M, Brown J M. A possible etiological role for ascorbate in calculi formation. Clin Chem 1986; 32:333-6

- http://www.vitamincfoundation.org/forum/viewtopic.php?f=10&t=9503&p=27949&hilit=calculi+formation#p27949

Also, Dr. Thomas Levy addresses the oxalate issue on this forum here:http://www.vitamincfoundation.org/forum/viewtopic.php?f=3&t=7701&p=19277&hilit=encapsulated#p19277

[studentroland]

[ofonorow]

Yes, I second that notion that Hickey and Robert's TARNISHED GOLD is a must read and explains the fallacy that is "evidenced based medicine."

So to the question, what is the risk of vitamin C causing kidney stones?

a) If vitamin C (ascorbate) played a significant role, than why don't animals, the majority of which make their own ascorbate 24/7 in amounts about two orders of magnitude higher than the Government RDA, suffer kidney stones in great numbers?

b) As M- pointed out, kidney stones are virtually nonexistent in the two clinical practices that used the highest amount of sustained vitamin C. The Riordin clinic and Cathcart's practice.

c) Any discussion of oxalate a) only applies to a subset of the stones, and b) is probably not applicable given the Hoffer review of the Japanese who were unable to duplicate the oxalate results found all over medical text books. Dr. Sheffery was a terrific vitamin C supporter, but he was a dentist. He wrote under the assumption that medical textbooks were correct about the oxalate issue.

d) These fictional studies/stories in the media are aimed at medical doctors. They are designed to reinforce what is taught (or in this case not taught) in medical school. If they happen to sway members of the public away from taking vitamin C, all the better for Big Pharma.

e) If there really was such an effect, even on 1/16 of one percent of the population, it should be easy to conduct a repeatable experiment that shows it. Where are these experiments?

f) B6 and magnesium will prevent kidney stones from forming.

g) Pauling's book explains why about half the stones that form (in alkaline urine) are prevented by taking asorbic acid. And that for the stones that generally form in acidic urine, one would be prudent to take their vitamin C as the alkaline sodium ascorbate.