What Protects the Heart May Also Ward Off Kidney Stones

TUESDAY May 17, 2011 -- The same lifestyle factors that are linked to healthy hearts and bones can also keep painful kidney stones at bay, a series of new studies suggests.

Researchers presenting data on Tuesday at the American Urological Association's annual meeting in Washington, D.C., contended that aspects such as diet, weight, calorie and calcium intake and medication usage can determine whether adults will develop kidney stones.

While the biggest risk factor for kidney stones is dehydration, according to the U.S. National Institutes of Health, this common condition can also be hereditary or caused by many other factors.

"Stone disease has been a problem since people have been around," said Dr. Marshall L. Stoller, who co-authored a study indicating women with higher calcium intakes were at reduced risk of the problem. "Only one disease is mentioned in the Hippocratic oath -- stone disease."

"Women should not lower their calcium intake in hopes of lowering their risk for calcium-based kidney stones," added Stoller, vice chair of the urology department at the University of California, San Francisco. "Those women who cut down their calcium increased their risk. It's sort of counterintuitive."

In addition to Stoller's study, other studies presented at the meeting suggested:

  • Reducing daily calorie intake may significantly lower the risk for stone disease in overweight and obese people. Scientists from the University of California, San Francisco used data on 78,551 participants from the Women's Health Initiative study to examine diet, body mass index (BMI, a ratio of weight to height) and stone disease.
  • Meat-heavy diets may be linked to a higher risk of developing kidney stones. Researchers from the University of Oxford, England, studied 50,617 people, finding that fresh fruit, fiber and certain minerals may reduce risk. No association was found with consumption of vegetables, calcium or vitamin C.
  • Higher levels of antioxidants in the body may lead to a lower risk of stone formation. Researchers from the University of Iowa found that alpha-carotene, beta-carotene and beta-cryptoxanthin -- antioxidants found in legumes, nuts and grains -- were linked with lower numbers of kidney stones among 17,695 survey participants in the National Health and Nutrition Examination Survey (NHANES III).
  • Statins, typically used to treat high cholesterol and triglyceride levels, were linked with a 50 percent reduction in stone disease among men and a 70 percent reduction among women, according to researchers. Scientists from the University of California, San Francisco, analyzed 57,320 patient records from a 10-year review of the Armed Forces Health Longitudinal Technology Application database, finding high cholesterol was linked with kidney stone formation and statins greatly lowered the risk.

"This has never been demonstrated before -- it's completely novel," said Dr. Roger Sur, author of the statin study and now director of the Comprehensive Kidney Stone Center at the University of California, San Diego. "It's a retrospective study, and it needs more rigorous prospective data. But it's certainly exciting information we hope to take forward."

With the link between lifestyle factors, heart disease and kidney stones so apparent, Stoller said, those who develop stones might want to consider if they are developing heart disease as well.

"If you have a stone, it could be looked upon as a canary in a mine shaft. You could be at risk for heart disease," he said. "We give our patients with stones three global recommendations: lower their salt intake, lower animal protein intake and get adequate fluid intake. That is [also] a cardiac-healthy diet."

Dr. Michael A. Palese, an associate professor of urology at Mount Sinai Medical Center in New York City, said the new studies add "ammunition" to advice he already gives his kidney stone patients about how to avoid future episodes.

"These are little things we do over time to stack the deck in the patient's favor," said Palese, who was not involved in the research presented. "I think this is an interesting addition to what we already know."

The studies presented at the meeting demonstrated an association with the assorted lifestyle factors and kidney stones, but did not prove a cause-and-effect. And experts note that research presented at medical meetings doesn't receive the same level of scrutiny given to studies published in peer-reviewed journals.

More information

For more on kidney stones, visit the U.S. National Institute of Diabetes and Kidney Diseases.

Posted: May 2011


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