Saturday Sept 14, 2013 (foodconsumer.org) -- Some research suggests that taking a high dose of vitamin C or ascorbic acid for a long term may increase the risk of the formation of kidney stones.  But some basic chemistry allows you to understand that this vitamin won't cause kidney stones or bladder stones in a person who follows a healthy diet and has a normal urinary pH.

First, studies that find a link between vitamin C supplementation and risk of kidney stones are observational and they do not provide any firm evidence to show vitamin C supplementation is the cause for the increased risk of kidney stones in a study population.

Second, the likely culprit if vitamin C is indeed responsible for the formation of kidney stones is calcium ascorbate.  However, calcium ascorbate is highly soluble in normal urine at pH 7.0 and it at a fairly high concentration can't stay in a solid state in urine at this pH.  According to wikipedia, 50 grams of calcium ascorbate can completely dissolve in 100 ml water whose pH is about 7.  A person can have daily 1000 to 2000 ml of urine whose pH is normally close to that of water.  And no one can have 50 grams of calcium ascorbate to dispose daily.  Considering both factors, it is impossible that taking ascorbic acid increases the risk of kidney stones  in a person who has urine with a normal pH.

Now, urine pH can range from 4.6 to 8 with 7 the normal level and this pH depends on a person's diet and medications he is taking.   A diet with high meat and low vegetables can cause a low urinary pH and increase risk of kidney stones.  At a low pH, the solubility of calcium ascorbate can be decreased and some calcium ascorbate may potentially be in a solid state, which can contribute to the formation of kidney stones.  In this case though, a weaker acid, uric acid can be a more riskier factor than ascorbic acid for the formation of kidney stones.  It is known that  acidic urine can promote the formation of stones of uric acid in the kidneys, ureters, or bladder. 

Thus, it is extremely unlikely that taking a few grams of ascorbic acid per day would increase the risk of the formation of kidney stones in a person who has a normal urinary pH.

Kidney stones of any type can be easily prevented by simply maintaining a high urinary pH.   A high urinary pH can be achieved by taking a healthy diet, or taking some supplements like potassium citrate or sodium bicarbonate pills from time to time.  Simply using some baking soda in drinking water can also help increase the pH and help prevent kidney stones.   It can also help when you use vitamin C, use sodium ascorbate, which is a strong base.

Additionally, a person's diet can affect the urinary pH.  Do some research using keywords "alkaline foods" to find out which foods can help maintain a normal pH.  

Lastly, check out the pH of your drinking water, which can range from 6.0 to 9.0 with 7 to 7.2 desired.   Acidic drinking water can not only destroy your teeth, but also increase the load of acids into your system and increase your risk of kidney stones among other things.(DL)

(This article is a comment and the opinions are the author's, and the author is not reliable for any loss caused by your using or misusing the information.)