For many years it was commonly thought that vitamin C was the cause of a painful urinary tract problem called nephrolithiasis, or kidney stones. The risk of developing kidney stones from taking vitamin C, however, is based only on weak scientific evidence, according to Linus Pauling Institute. Vitamin C is generally safe and beneficial for a number of physiological processes, even at high doses.
Biochemistry of Vitamin C
Vitamin C, or ascorbic acid, is a water soluble chemical obtained from foods. It's an essential nutrient for making collagen, a basic chemical component of connective tissues. Connective tissues are found throughout the body in such structures as muscles, ligaments and blood vessels, which makes collagen important to the body. Vitamin C deficiency can lead to scurvy, a potentially fatal condition in which connective tissue forms abnormally. Scurvy's symptoms include bleeding, hair and tooth loss, joint swelling and pain.
Kidney Regulation
When vitamin C is broken down through metabolism, a chemical called oxalate is released into the blood. This is a natural waste material or metabolite that must be flushed from the blood in order to avoid build up. The kidneys are responsible for removing oxalate and other waste material such as uric acid. Under normal conditions, they do so effectively, while simultaneously regulating water and electrolyte levels in the body.
Urinary Stones
Urinary stones are accumulations of waste products in the blood that become mineralized. It is not known why some people develop stones, yet stones are not uncommon and can be quite painful, sometimes require hospitalization. Most stones are made of oxalate, the product of vitamin C metabolism. When the kidney cannot flush the oxalate from the blood, it begins to accumulate in the urinary system. In time and with continued accumulation, an oxalate stone begins to form.
Fact and Fiction
The Linus Pauling Institute says that the long-held belief that vitamin C causes kidney stones stems from the well-known association of high serum oxalate levels with stone formation. However, there is little scientific evidence available to support the association of high oxalate levels, vitamin C intake and kidney stones. The benefits of vitamin C for fighting cardiovascular disease, cancer, stroke, gout and supporting the immune system far outweigh any weak association with kidney problems. The Recommended Daily Allowance for vitamin C is 75 to 90 mg for adults older than age 19.
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