New dietary approach may help prevent kidney stones

“I’d rather give birth to an elephant.”

That kind of imagery sticks in your mind. I know it stuck in mine.

That was the description my colleague Pat used to convey the pain of a kidney stone. I included it in the e-Alert I sent you on November 20 about this excruciating condition. Back then, I was writing to tell you about a new study that showed the essential fatty acid eicosapentaenoic acid (EPA) could help prevent kidney stones. But ever since, I’ve been on the look-out for more information. I just couldn’t get Pat’s description out of my mind – and I wanted to be able to help her, and the tens of thousands of other people like her.

Now, a new study reports the kidney-stone-prevention diet that doctors have been recommending for years doesn’t work. That’s the bad news. But the good news is, the same study reveals what DOES work to reduce the urinary markers of kidney stones and reduce your risk of recurrence.
Does a low calcium diet REALLY help prevent kidney stones?

First, a bit of background: there are several different kinds of kidney stones, but 70 to 80 percent are composed of calcium and oxalate (also called oxalic acid). Oxalate is type of salt found in certain foods, like walnuts, spinach, rhubarb, parsley, and chocolate. Consequently, doctors have long advised kidney stone sufferers to lower their calcium intake to help prevent recurrences. But long-term research failed to show a benefit from this approach – and kidney stone recurrence rates remained right around 50 percent.

Some limited research had suggested that animal protein and salt intake might have more to do with kidney stones than calcium. So in this study, the researchers set out to compare the two dietary approaches. They recruited a group of 120 men with a history of calcium oxalate kidney stones; the participants had to have urinary calcium excretion greater than 300 mg per day and at least two documented kidney stone events. Then they divided the men into two equal groups. One group followed a traditional low-calcium diet, with only about 10 mmol of calcium intake each day (about 400 mg).

The other group followed a low-protein, low-salt diet, with normal-to-high intake of calcium. Low protein was defined as 15 percent of total calories, or about 90 grams of protein for a 2500 calorie diet. Sodium was restricted to 50 mmol per day or less (about 2000 mg). Both groups were told to avoid foods rich in oxalate, and to increase water intake to two liters a day in cold weather and three liters a day in warm weather. Each man’s urine was evaluated at baseline, one week after randomization, and then once a year for five years (or until he had a recurrence.)
Dietary approach cut kidney stone recurrence rate in HALF

Over time, the low-protein, low-salt approach produced dramatic results. In the low-calcium diet group, 23 of the 60 participants had a recurrence. But in the low-protein group, only 12 of the 60 had another stone incident. That’s HALF the recurrences, just from a dietary change.

Ironically, the low-protein group showed as much reduction in urinary calcium excretion as the low-calcium group – even though they consumed normal to high levels of calcium. But the low-protein group also decreased its excretion of oxalate, the other component of most kidney stones. In fact, in the low-calcium group, the oxalate excretion actually INCREASED.

As I mentioned, I’ve written about kidney stones before. And I’ve told you about two available options to prevent them: EPA, which is readily available in health food stores, and chanca piedra, the Amazonian herb extract, available from Raintree Nutrition (www.rain-tree.com or 800-780-5902). Now, here’s another approach that you can adopt, either alone or in conjunction with these supplement therapies. If you know someone who lives in fear of their next kidney stone attack, please pass this information along.

Source:
New England Journal of Medicine 2002; 346:77-84

Copyright 1997-2002 by Institute of Health Sciences, L.L.C.