Most supplements for stones not backed by science

Kidney stone patients take a variety of dietary supplements that claim to treat or prevent kidney stones. While consumer reviews for the supplements tend to be positive, most of the supplements and their ingredients have conflicting or no scientific evidence to support the claims, according to a recent study.

“Patients have been asking my colleagues and me about supplements on the market claiming to treat or prevent kidney stones. What we didn’t know was how many of them there are and what a huge variety of ingredients they contain,” said first author Kevin Koo, MD, MPH, MPhil, instructor of urology and fellow in endourology and minimally invasive urologic surgery at Johns Hopkins University School of Medicine, Baltimore.

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“These supplements are readily available at health food stores and online. Online marketplaces like Amazon and Google have made it easier than ever for patients to do a quick search for a supplement or herbal remedy, order it, and start using it without ever really talking to their urologists about it or its expected benefits or risks,” added Dr. Koo, who presented the findings at the 2019 World Congress of Endourology and SWL in Abu Dhabi. The study was subsequently published in the Journal of Endourology (Jan. 13, 2020 [Epub ahead of print]).

Johns Hopkins researchers studied the kidney stone supplement landscape, including marketing tactics used to entice consumers’ use. They also assessed the evidence for ingredients in the supplements to help urologists give patients evidence-based recommendations.

They analyzed a total of 56 nonpharmacologic active ingredients contained in 27 supplements that made specific claims related to kidney stones.

“Many of these supplements claimed to dissolve kidney stones, prevent new stones from forming, or reduce stone-related symptoms,” Dr. Koo said.

Nineteen, or 70%, of the supplements studied claimed they could be used to support kidney health. The average 30-day cost for taking a supplement was $32, and ranged from $4 to $189.

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They found that nearly all the products were highly rated, with 21 products having 4- or 5-star ratings (out of 5). Users giving reviews often claimed their stones dissolved or stone pain went away when they took specific supplements. Based on the reviews, patients thinking about using a supplement could think it would be highly effective, Dr. Koo said.

But scientific evidence of their effectiveness was largely nonexistent. The authors’ literature review revealed that of the 56 ingredients studied, 84% had no published studies for use in stone disease; 16%, or nine ingredients, had any published studies for use; and only 9% had studies supporting their use.

In the 18 scientific publications about the ingredients that the authors identified, six showed mixed or no benefit for stone disease; the other 12 publications supported the ingredients’ use in stone formers. Only five were human studies.

Chanca piedra/Phyllanthus niruri showed some evidence of efficacy and was the most studied active ingredient, with human and animal studies. Cranberry, green tea leaf, pomegranate, Tribulus terrestris, and citric acid followed as ingredients with human studies for treating stone disease.

But Dr. Koo said he is hesitant to recommend any supplemental ingredients based on the quality of science available today.

“Even when studies were available, they were often studies done in animals or humans where the outcomes were biochemical changes in the serum or urine-not specifically changes in stone formation or stone recurrence,” Dr. Koo said. “So even with studies that concluded that there might be useful or effective biochemical changes that would potentially lead to decreased stone formation, we don’t know for sure in the vast majority of cases whether consuming that particular ingredient actually results in meaningful changes for our patients.”

Overall, there is very limited evidence, but there are a lot of supplements on the market and patients need to have real expectations of what these supplements may or may not do regardless of their claims, according to Dr. Koo.

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“We need to remind our patients that the absence of scientific evidence does not mean an absence of potential harm. In these cases, we simply don’t have definitive studies that allow us to say for sure that using these supplements or using specific ingredients is expected to lead to meaningful changes in stone recurrence or stone formation risk,” he said.

Another message from the study is that urologists should include dietary supplement use when asking patients about other medications they’re taking or have tried for their stone disease.

“We should remind ourselves as clinicians that stone disease is a chronic disease and that the medical and surgical management of stone disease can be very challenging and burdensome for patients. There’s a reason patients look for dietary supplements to help them with their symptoms or with their stone recurrence: Stone disease can create a lot of morbidity and anxiety,” he said. “I think including dietary supplements in our routine counseling can open up an opportunity for a dialogue with the patient about what works, what might work, what doesn’t work, and the evidence behind all the different strategies that our patients might be trying.”

One possible explanation for the positive product reviews is that many supplement labels instruct people to take the products three times per day with 12 ounces of water each time. That’s almost 40 ounces of water, which is about half of what urologists would typically recommend for stone patients to be drinking for fluid intake.

“It’s possible that increased fluid intake is what’s driving some of the user-reported benefits,” Dr. Koo said.