Vitamin C Does NOT Cause Kidney Stones

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Tue, 5 Jul 2005 07:51:32 -0500

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Vitamin C Does NOT Cause Kidney Stones

 

 

 

 

 

For Immediate Release:

 

VITAMIN C DOES NOT CAUSE KIDNEY STONES

 

(Orthomolecular Medicine News Service, May 23, 2005)

 

By Steve Hickey, PhD and Hilary Roberts, PhD.

 

It is strange how some medical authors seem desperate to show that

vitamin C causes harm. One recurrent scare story is that vitamin C might

cause kidney stones. However, although such warnings pop up regularly,

these reports do not demonstrate an increase in the number or size of

stones; instead, they rely on vague indicators of improbable risk.

 

The authors of such uncritical papers have probably not read the

literature, for this is an old story. Decades ago, the idea that

vitamin C

causes kidney stones formed part of the medical attack on Linus Pauling.

While it was initially a reasonable hypothesis, unexpected kidney

stones are not found in people taking large amounts of vitamin C. (1,2)

 

There is no evidence that vitamin C causes kidney stones. Indeed, in

some cases, high doses may be curative. (3) A recent, large-scale,

prospective study followed 85,557 women for 14 years and found no

evidence

that vitamin C causes kidney stones. (4) There was no difference in the

occurrence of stones between people taking less than 250 milligrams per

day and those taking 1.5 grams or more. This study was a follow up of

an earlier study on 45,251 men. This earlier study indicated that doses

of vitamin C above 1.5 grams reduce the risk of kidney stones. (5) The

authors of these large studies stated that restriction of higher doses

of vitamin C because of the possibility of kidney stones is

unwarranted.

 

People with recurrent stone formation may have an unusual biochemistry,

leading to increased production of oxalate from vitamin C. (6) Oxalate

and urate can accumulate in kidney stones. In practice, there is an

increased excretion of both oxalate and urate with gram level doses of

vitamin C (ascorbate). Various authors over the years have used this

increase to predict that vitamin C will cause kidney stones; however,

these

predictions have never been confirmed.

 

Around three quarters of all kidney stones are composed of calcium

oxalate; unlike some other stone types, these can form in acidic urine.

Although vitamin C does increase the production of oxalate in the body,

there is no evidence that it increases stone formation. It could even

have the reverse effect, for several reasons. Firstly, vitamin C tends to

bind calcium, which could decrease its availability for formation of

calcium oxalate. Secondly, vitamin C has a diuretic action: it increases

urine flow, providing an environment that is less suitable for

formation of kidney stones. Finally, stone formation appears to occur

around a

nucleus of infection. High concentrations of vitamin C are bactericidal

and might prevent stone formation by removing the bacteria around which

stones form.

 

Vitamin C could also prevent other types of kidney stones. Less common

forms of stone include uric acid stones (8%), that form in gout, and

cystine stones (1%), which can occasionally be formed in children with a

hereditary condition; these stones are not side effects of vitamin C.

Other stones include those made from calcium phosphate (5%), which

dissolve in a vitamin C solution. Acid urine, produced by ascorbate, will

also dissolve the struvite stones (magnesium ammonium phosphate) that

often occur in infected urine.

 

Recently, Linda Massey and colleagues from Washington State University

have claimed that vitamin C increases the risk of kidney stones. (7)

Their paper illustrates how the claims of risk have little basis in fact.

Massey claims that vitamin C supplementation can increase the amount of

oxalate. Vitamin C can increase oxalate absorption and, if degraded in

the body, ascorbate can be converted into oxalate. However, while

oxalate is a constituent of some types of kidney stone, an increase in

its

concentration does not mean that more or larger kidney stones will be

formed. The formation of kidney stones is influenced by many factors and,

as we have seen, vitamin C might be predicted to inhibit several

aspects of stone generation. Massey suggests that this increase in

oxalate

may increase the risk of stones. This is a weak suggestion, which is

contradicted by substantial evidence, quoted above.

 

This evidence suggests that a high vitamin C intake has no effect on

the number of kidney stones, or may even be protective.

 

Massey links oxalate to risk by use of a measure called the Tiselius

Risk Index or TRI. (8) However, this measure is applied incorrectly.

Indeed, in the presence of high doses of vitamin C, this index should be

modified to accommodate the formation of calcium ascorbate in urine. The

TRI measure was developed for subjects that had not been supplemented

with vitamin C and, on the basis of simple chemistry, requires

modification for use with ascorbate supplementation. Since vitamin C

might

affect many stages of stone formation and growth, application of the TRI

measure to supplemented individuals is suspect. The TRI is applied in

this

case as a predictive measure, for which it has not been validated.

Furthermore, the TRI is derived from the concentration of calcium

oxalate,

making the argument for increased risk rather circular. Even more

importantly, Massey uses the TRI to predict an increased theoretical

risk,

which substantial evidence indicates is absent.

 

In Massey's study, 29 stoneformers and 19 non-stoneformers were

supplemented with one gram of vitamin C, twice each day. After five

days on a

low-oxalate diet, the subjects were challenged before breakfast with

136 mg oxalate, including 18 mg oxalic acid. They remained on the low

oxalate diet for the remainder of the day. Of the 48 people, 12

stoneformers and 7 non-stoneformers had an increased total oxalate

excretion of

greater than 10% after supplementation.

 

However, the number or size of kidney stones did not increase.

 

Also, we can note that seven of the subjects who showed an increased

level of oxalate were not stoneformers. The important question of why

some people form kidney stones, and others do not, was neatly sidestepped.

 

Massey's argument boils down to the vague idea that there could

possibly be an increase in kidney stone formation in some rare people.

This

might be the case if vitamin C increased oxalate without affecting any

other part of the process; this is known to be false. If this is the sort

of evidence presented as acceptable, we can be comfortable with the

claim that the areas of the moon not yet visited by man may be made of

green cheese.

 

References:

 

1) Hickey S. Roberts H. (2004) Ascorbate: the Science of Vitamin C,

Lulu press.

 

2) Hickey S. Roberts H. (2004) Ridiculous Dietary Allowance, Lulu

press.

 

3) McCormick W.J. (1946) Lithogenesis and hypovitaminosis, Medical

Record, 159, 410-413.

 

4) 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.

 

5) Curhan G.C. Willett W.C. Rimm E.B. Stampfer M.J. (1996) A

prospective study of the intake of vitamins C and B6, and the risk of

kidney

stones in men, J Urol, 155(6), 1847-1851.

 

6) Chalmers A.H, Cowley DM, Brown J.M. (1986) A possible etiological

role for ascorbate in calculi formation, Clin Chem, 32(2), 333-336.

 

7) Massey L.K. Liebman M. Kynast-Gales S.A. (2005) Ascorbate increases

human oxaluria and kidney stone risk, J Nutr, 135(7), 1673-1677.

 

8) Tiselius H.G. (2000) Stone incidence and formation, Clinical Urology

26(5), 452-462.

 

What is Orthomolecular Medicine?

 

Linus Pauling defined orthomolecular medicine as " the treatment of

disease by the provision of the optimum molecular environment, especially

the optimum concentrations of substances normally present in the human

body. " Orthomolecular medicine uses safe, effective nutritional therapy

to fight illness. For more information: http://www.orthomolecular.org

 

Take the Orthomolecular Quiz at

http://www.orthomolecular.org/quiz/index.shtml

 

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and non-commercial informational resource.

 

Editorial Review Board:

 

Abram Hoffer, M.D., Ph.D.

Harold D. Foster, Ph.D.

Bradford Weeks, M.D.

Carolyn Dean, M.D., N.D.

Eric Patterson, M.D.

 

Andrew W. Saul, contact person. email: omns .

 

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