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Some Diet Sodas May Ward Off Kidney Stones

WEDNESDAY April 29, 2009 -- Drinking diet sodas, especially those with a citrus flavor, might help ward off painful calcium deposits known as kidney stones.

The drinks contain citrate, which is known to inhibit calcium formation, according to the authors of a study that was to be presented Sunday at the American Urological Association annual meeting, in Chicago.

And there's more good news in the drinks department: A second study being presented at the same meeting found that pomegranate juice might slow the progression of prostate cancer.

Some 10 percent of people in the United States will form these calcium deposits, known as kidney stones, at some point in their lives. In as many as a third of the cases, it's because they do not urinate enough citrate, said study author Dr. Brian Eisner, a clinical fellow in urology at the University of California San Francisco and an instructor in urology at Massachusetts General Hospital/Harvard Medical School, in Boston.

Potassium citrate and other pills can help alleviate the problem, as can a special lemonade drink (rich in citric acid) concocted by one of Eisner's co-authors a decade or so ago.

But this study extended the idea to see how much citrate was contained in 15 commonly consumed diet sodas. The authors did not look at regular sodas because of the potentially unhealthy sugar content.

"They're measuring certain ingredients in diet sodas which are known to have an activity against kidney stones," said Dr. Patrick Lowry, an assistant professor of surgery at Texas A&M Health Science Center College of Medicine and section head of laparoscopy and endourology at Scott & White Memorial Hospital in Temple.

Eight of the soda types had as much as or more citrate than the original lemonade formula. The highest performers were Diet Sunkist Orange, Diet 7-Up and Diet Canada Dry (Diet Coke with Lime had no citrate).

"This is nice because patients have to drink fluid anyway to protect them from kidney stones," Eisner said. The current recommendation is two liters of fluid per day for people who have kidney stones.

But another expert wasn't convinced.

"I think it would be farfetched to think everyone should drink diet soda for kidney stones," said Dr. Michael Palese, director of minimally invasive surgery at Mount Sinai Medical Center in New York City. "You can argue that other things in the soda, like caffeine, would be detrimental because it will dehydrate you. Water is one of the better ways to go."

"This isn't for everybody and for people with severe low citrate, it's probably not that great," added Eisner, who is gearing up for a study to see if these diet drinks lower urinary citrate levels in actual humans.

The second study, led by urologist Dr. Allan Pantuck of the University of California, Los Angeles, found that prostate-specific antigen (PSA) levels among a small group of patients drinking eight ounces of pomegranate juice daily took significantly more time to double compared with men not drinking the juice.

High PSA levels can indicate the presence of a prostate tumor, although the test is not fail-safe.

"The fact that it actually slows progression by measuring a tumor marker is a pretty big deal," Lowry said. "There's really very little out there that has much activity against active prostate cancer."

Although the evidence is far from conclusive, experts seemed to agree that there were few reasons not to drink pomegranate juice.

"When patients ask me if they should take vitamin E, selenium, wheat grass juice, I'll say nobody's studied any of this stuff," said Dr. Simon J. Hall, director of The Deane Prostate Health and Research Center at Mount Sinai Medical Center in New York City. "At least with pomegranate, somebody did and it appeared to have some efficacy."

"The only potential downside is that it's a semi-high-calorie juice, but if you have prostate cancer, that's probably the least of your worries," Lowry stated. "And if they can show activity against prostate cancer, then this might spur some research in the area of prostate cancer prevention. That's really key. The disease affects one in six men. Anything that can affect prevention of prostate cancer is very important."

The researchers, all of whom had received money from POM Wonderful pomegranate juice, used the product for the study.

More information

There's more on kidney stones at the U.S. National Institute of Diabetes and Digestive and Kidney Diseases.

Posted: April 2009


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