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Could Your Eye Vitamin Cause Kidney Stones?

Important news for users of eye vitamins containing high doses of zinc: a study has linked high levels of zinc with kidney stones. Published in the prestigious scientific journal PLOS ONE, the study revealed that high levels of zinc in the body may contribute to kidney stone formation.

According to the National Institutes of Health (NIH), kidney stones are one of the most common disorders of the urinary tract, affecting nearly 10 percent of the U.S. population. Each year in the U.S., people suffering with kidney stones make over a million visits to health care providers, including over 300,000 visits to emergency rooms due to the pain. While kidney stones are more common in adults, they also are becoming increasingly common in infants, children, and teenagers from all races and ethnicities.

Kidney Stone Surface
Surface of a Kidney Stone. Photo Credit: Kempf EK.

What Are Kidney Stones?

Kidney stones are hard, often jagged masses of crystallized minerals that form in the kidney. Some kidney stones are very small and pass through the body without even being noticed. Larger stones may get stuck in the urinary tract, however, causing severe pain and blood in the urine.

"Nearly 90 percent of kidney stones are calcium-based, but we really don't know what causes those stones to form," says Dr. Killilea, a staff scientist at Children's Hospital Oakland Research Institute (CHORI), and co-author of the study. "In the past, urologists recommended limiting the amount of calcium in the diet to help prevent the formation of kidney stones, but that did not turn out to be very useful. So we wanted to learn what other factors might contribute to the formation of kidney stones."

Working with fruit flies, researchers were able to make a correlation between high levels of zinc and kidney stone formation. Dr. Killilea stresses that the results of the study are still new, so it is too early to know about the impact of zinc levels on human kidney stone formation.

"This study's results do not mean that zinc is bad for you–in fact, quite the opposite," he says. "Zinc is an essential element in the human diet. It is well known that people with a zinc deficiency have immune systems that don't function as well, and that might make kidney stone disease worse. It is only very high levels of zinc that might be a problem.

With the fruit flies, large doses of zinc caused them to produce stones faster and to produce bigger stones.

People should not avoid zinc, but we need to determine what the optimal levels of zinc might be, especially in people at risk for stone disease.

That information might eventually give us tools to treat or even prevent kidney stone formation."


The above post is reprinted from materials provided by UCSF Benioff Children's Hospital Oakland. Materials may be edited for content and length.

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