New research suggests zinc — a common element in many foods and vitamin supplements — may promote kidney stone formation.

High levels of zinc may be “the core by which stone formation starts,” concluded researchers with the University of California-San Francisco, who published their findings in the Public Library of Science journal PLOS ONE.

"The ultimate goal of our research team is to prevent kidney stones from happening in the first place and to understand the mechanisms by which they form a part of that effort," said lead researcher Thomas Chi, MD.., an assistant professor of medicine in the UCSF Department of Urology. His research involved fruit flies, which produce stones similar to those in humans.

The new findings suggest zinc interacts with oxalate, calcium, and other minerals that make up kidney stones.

"The idea made sense, because our most recent research demonstrates that zinc is important for the mineralization and calcification processes that lead to urinary stones," said Chi.

The findings showed that changes in oxalate levels in the urine, which is a known risk factor for kidney stones, were affected by dietary zinc intake: as zinc dropped, urinary oxalate changed dramatically.

The prevalence of kidney stones has been rising in the United States over the last three decades. The lifetime risk of kidney stones is now approximately 19 percent in men and 9 percent in women.
Possible causes include drinking too little water, exercising too much or too little, obesity, weight loss surgery, or eating food with too much salt or sugar.

"Once you have developed a first stone, as many as 50 percent of people are at risk of developing another stone within five years," said Chi. "Amazingly, we have not had a new medication for the prevention of kidney stones in more than 25 years, and the medications that we do have aren't completely effective."

Zinc is found in vitamins and many foods — including oysters, liver, lamb, beef, spinach, wheat germ, beans, mushrooms, and cocoa — that health experts say should be eaten in moderate amounts.