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Skipping stones: how to avoid kidney stones.


I felt like I had been shot," remembers 59-year-old Bethesda, Maryland, writer Ron Collins. "One moment I was standing, then all of a sudden I was lying on the floor in agony. I had no idea what was going on. I was absolutely helpless."

In excruciating pain in his lower abdomen, Collins was rushed by his wife to the hospital emergency room, where he was diagnosed with a kidney stone and admitted for treatment.

"The experience humbled me very quickly," he says. "I'll never forget it."


About one in seven men and one in 15 women will be diagnosed with kidney stones during their lifetime. On a typical day, more than 1,300 of them will wind up in hospital emergency rooms.

And the number of people with stones is rising, according to kidney stone expert Gary Curhan, an associate professor of medicine at Harvard Medical School. The incidence of kidney stones jumped roughly 35 percent between 1980 and 1994, the most recent year studied.

"At least part of the rise may be explained by the growing number of Americans who are overweight," notes Curhan.

And more people are getting ultra sounds and CAT scans for other reasons, adds David Goldfarb, clinical chief of the nephrology division at the New York University Medical Center. Those tests can reveal (often-harmless) "silent" stones that wouldn't otherwise have been noticed.



A kidney stone is a solid mass that forms in the kidneys from substances normally found in the urine typically calcium combined with oxalate or phosphate.

If the crystals remain small enough, they can pass out of the body in the urine without causing discomfort. But some stones become as large as pearls, or even golf balls, and some have jagged surfaces.

If they get stuck somewhere along the urinary tract, they can cause serious pain. "If you get recurring kidney stones, you may end up with an infection and kidney damage," notes Curhan.

Men are twice as likely to be diagnosed with kidney stones as women. Rates peak in a man's 40s or early 50s, while "our data suggest that rates are higher for women in their 20s and 30s," says Curhan.

Family history matters. Men were two and a half times more likely to have stones if a parent or sibling had them, according to a study of 38,000 men from the Health Professionals Follow-Up Study. (1)

Where you live may also count. In one study, residents of the southeastern United States had roughly a 20 percent greater likelihood of being diagnosed with kidney stones than people in other parts of the country. (2) Some researchers have dubbed the Southeast the "Stone Belt."

What's the connection? One hypothesis: warm weather makes you sweat, which makes your urine more concentrated if you don't compensate by drinking more fluids. And concentrated urine is a breeding ground for kidney stones.

"When people relocate from areas of moderate temperature to areas with warmer climates, there is evidence that the risk of stones increases," notes urologist Margaret Pearle of the University of Texas Southwestern Medical Center in Dallas.

Gender and family and, sometimes, geography you can't choose. Here are two factors that you may be able to do something about:

* Overweight, The effect of weight on kidney stones is compelling, says Gary Curhan. He and his colleagues tracked the 46,000 men in the Health Professionals Follow-Up Study, the 94,000 older women in the Nurses' Health Study I, and the 102,000 younger women in the Nurses' Health Study II.

"In all three studies, the more people weighed, the greater their risk of kidney stones," says Curhan.

In fact, women who gained more than 35 pounds since young adulthood were about 75 percent more likely to get kidney stones than women who didn't gain weight, and men who gained more than 35 pounds were about 40 percent more likely. (3)


That's no surprise. Researchers know that overweight people excrete more calcium and oxalate in their urine, which increases the risk of stones.

* Diabetes. In the two Nurses' Health Studies, women who had been diagnosed with diabetes were 30 to 60 percent more likely to develop kidney stones than women who hadn't been diagnosed. (4)

"We don't know for certain why," says Curhan, "but a lot of things happen when people become insulin resistant and diabetic. The ability of the kidneys to excrete acid changes, which affects the acidity of the urine, for one thing. And that could affect the formation of stones."


"Most people will pass their kidney stones spontaneously and won't wind up in the operating room," says NYU's David Goldfarb, who is also director of the Kidney Stone Prevention Program at Saint Vincent Medical Center in New York.

"And although having kidney stones may be intensely painful, inconvenient, and expensive, it's not life-threatening in most instances."

But stones may be a warning of more serious problems.

"People who develop kidney stones have a greater risk of developing hypertension later," says Curhan. "We don't know why. It's possible that both have the same underlying cause." It's also possible that some treatments for stones damage the kidneys and lead to higher blood pressure.

"People with kidney stones are also more likely to suffer from osteoporosis," says Curhan. "They often are losing excessive calcium in their urine, and that calcium tends to come from their bones."

Bottom line: kidney stones may not be an isolated problem.

"I tell my patients that the kidney stones which brought them to my office may be the least of their problems, and that the stones are a harbinger of their increased risk for diabetes, high blood pressure, and osteoporosis," says Goldfarb. "Having a first kidney stone is often a reason to be screened for those other diseases."



"Once someone has suffered a kidney stone, they should recognize that much can be done to prevent more from forming," says Curhan.

"First, you should find a urologist or nephrologist who's willing to make a long-term investment in trying to prevent you from getting recurrent kidney stones and who has experience in doing that." Most plans include one or more of the following:

* Drink lots of fluids. "Crystals form when the urine gets too concentrated," says Curhan. "If people drink too little, their urine becomes more concentrated and they're more likely to have stones."

Among 200 Italians who had been diagnosed with a first kidney stone, those who were counseled to drink eight eight-ounce glasses of water a day were less than half as likely to have more stones over the next five years as those who weren't told to drink more. (5)

Maryland author Ron Collins started drinking more fluids after his harrowing experience. "Ten years after my first and only stone, I still faithfully drink lots of liquid and always have a bottle of water next to my bed."

* Don't cut calcium. Kidney stones are mostly calcium, so it's no surprise that, for years, doctors told their patients with stones to consume less calcium.

"That was wrong," says Curhan, who was the first researcher to find that the calcium in food actually reduces the risk of stones, at least in men under 60 and in women. (It seems to have no effect in older men.) (6)

In a five-year trial in Italian men (average age: 45) who had had at least one kidney stone, those who were assigned to a diet containing 1,200 milligrams of calcium a day were half as likely to be diagnosed with a new stone as those who ate a daily diet containing 400 mg of calcium. (7) (The National Academy of Sciences' Institute of Medicine recommends that men and women over 50 consume 1,200 mg of calcium a day.)

Calcium supplements don't appear to reduce kidney stone risk for anyone, and, in one study, slightly increased the (low) risk in women over 50. (8)

The calcium in food may lower the risk of stones by binding oxalate in the GI tract. The bound oxalate is excreted in the stool, which leaves less oxalate to be absorbed into the blood and later excreted in the urine.

Getting more calcium may not help as much, though, if you consume more salt.

"The more salt you eat, the more calcium you excrete in your urine," says Goldfarb. And cutting salt isn't easy, he notes. "Relying on processed foods and restaurant foods, which a lot of my patients in New York City do, makes it difficult."

* Coffee, yes. Grapefruit juice, no.


"The epidemiological studies consistently show that coffee drinkers have fewer stones," says Goldfarb. "We did a study of twins in which we found that if one twin had a kidney stone, that twin was much less likely to be a big coffee drinker." (9)

With one exception, citrus juices also help, because they increase the citrate content and reduce the acidity of the urine, both of which lessen the chances of stones forming, says Goldfarb.

"But the epidemiological studies consistently show that both men and women who drink a lot of grapefruit juice have more kidney stones," he adds. Researchers don't know why.

Soft drinks don't seem to have an impact, but cranberry juice does. And you won't see that mentioned in Ocean Spray ads. "Cranberry juice has oxalate in it," says Goldfarb, "so we don't recommend it to patients." The most common type of kidney stone is calcium bound to oxalic acid.

(According to analyses by Curhan's lab, high-oxalate foods include spinach, rhubarb, almonds, baked potato with skin, bulgur, beets, and navy beans.)

* Don't overdo vitamin C. Oxalic acid also explains why some kidney stone experts recommend against taking megadoses of vitamin C. Some of the vitamin is metabolized to oxalic acid in the body.

In three studies that gave a total of 139 people either 1,000 or 2,000 milligrams a day of vitamin C for three to six days, those taking 2,000 mg had higher oxalate levels in their urine, whether or not they had a history of kidney stones. (10)


Since last fall, close to 300,000 Chinese babies have been sickened--and at least six have died--after drinking formula made with milk contaminated with the industrial chemical melamine. Many had kidney stones.


Apparently, unscrupulous Chinese manufacturers added the melamine to make watered-down milk appear higher in protein. (Melamine is rich in nitrogen, and tests for protein often measure nitrogen.)

Melamine can crystallize in the kidneys and clog the tiny tubules that filter the blood. That can lead to stones, kidney failure, and death. Infants are especially vulnerable because formula is their main source of food, and because their tiny bodies get more melamine per pound of body weight.

Inspectors have found traces of melamine in imported Chinese foods in more than a dozen countries. In the United States, as of mid-November, melamine had turned up in a small number of foods--milk drinks, instant coffee, candy, and biscuits--sold mostly in Asian groceries. Officials suspect that it came from the foods' dairy ingredients. (For an updated list of recalled products and the latest government advisories, go to www.fda .gov/oc/opacom/hottopics/melamine.html.)

Most experts believe that those foods pose little risk. In fact, there

have been no reports of illnesses in children outside China or in adults in any country, including China.

But as a precaution, last November the U.S. Food and Drug Administration started detaining at the border all Chinese foods containing dairy ingredients until the manufacturers or buyers have them tested to show that they're free of melamine.

The Bottom Line

* If you're overweight or have diabetes, you're more likely to develop kidney stones. So try to lose (or avoid gaining) excess weight and keep physically active.

* If you've had a kidney stone, it may be a sign that you have an increased risk of diabetes, hypertension, and osteoporosis.

Throwing Stones

If you suffer from kidney stones, here are a handful of Web sites to stay away from.

* We'll Pass. "3 Grocery Items Painlessly Dissolve Kidney Stones," promises the Internet ad that directs you to And you can learn "how to get rid of the stones for good" by going to

Click on those ads, or others like them, and you'll find entrepreneur Joe Barton. "I have discovered and perfected a safe and natural home remedy that has helped thousands of other kidney stone sufferers dissolve their kidney stones into small, sand-like particles, and then pass them without pain," goes his pitch. Order Barton's "Kidney Stone Removal Report" from ($19.95) or from ($33.97) and the pain may shift from your kidneys to your wallet.

Barton is a South Dakota accountant who self-publishes some two dozen books dispensing medical advice on subjects ranging from depression to female hair loss. His "report" consists of a thin 40 pages of folklore about cures for stones. As it turns out, the "safe and natural home remedy" that Barton says he discovered ("it begins working immediately") can be found all over the Internet: consume a mixture of Coca-Cola, blenderized asparagus, and water.

There! And you don't even owe us a dime for the advice. Good thing, because you'd be overpaying. "Calcium stones will not dissolve, so any Internet claim about dissolving them is hogwash," says kidney stone expert David Goldfarb.


* A Household No-Name. "Is There a Way You Can Dissolve Your Kidney Stones And Become Pain Free With This Household Item You Already Use Every Day?" asks, which invites you to shell out $29 for a copy of the "Kidney Stones Guide."

What you'll get for your money from the unknown author is 54 pages of basic information about kidney stones--some of it outdated--that's available for free all over the Internet. That includes repeated advice to drink plenty of water. (Apparently, that's the magical "household item," though the guide never says so explicitly.)

* Clinically Shifty, "Quickly Disintegrate Your Kidney Stones And Find Relief Immediately Without Risky Surgery," promises "Uriflow is the only product that has over 20 independent clinical studies supporting its effectiveness."


Except that there aren't 20 studies of the 10 herbs in Uriflow, the most widely advertised kidney stone supplement on the Internet. We couldn't find a single one. And Uriflow's marketer, BioNeutrix Healthcare, wouldn't give us a list of the studies.

The company probably isn't looking for attention. In November 2006, the Food and Drug Administration warned BioNeutrix that it was making unapproved--and therefore illegal-drug claims for Uriflow on its Web site ( For example, the company claimed that Uriflow "has specific ingredients that are targeted to cause the stone's tiny particles to separate by micro-pulverization and dissolve back into your urine."

Not a problem. BioNeutrix simply shut down and shifted its operations to Two years later, kidneysite is still littered with dodgy claims...and the FDA has yet to catch on.

(1) J. Am. Soc. Nephrol. 8: 1568, 1997.

(2) J. Urol. 151: 838, 1994.

(3) J. Am. Med. Assoc. 293: 455, 2005.

(4) Kidney Int. 58: 1230, 2005.

(5) J. Urol. 155: 839, 1996.

(6) J. Am. Soc. Nephrol. 15: 3225, 2004.

(7) N. Engl J. Med. 346: 77, 2002.

(8) N. Engl J. Med. 354: 669, 2006.

(9) Kidney Int. 67: 1053, 2005.

(10) J. Nutr. 135: 1673, 2005.
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Title Annotation:SPECIAL FEATURE
Author:Schardt, David
Publication:Nutrition Action Healthletter
Article Type:Clinical report
Geographic Code:1USA
Date:Jan 1, 2009
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