Presentation Authors: Kevin Koo*, Tareq Aro, Brian Matlaga, Baltimore, MD
Introduction: An increasing number of dietary supplements have recently been brought to market with the purported benefit of kidney stone risk reduction. These products may be purchased without a prescription and carry claims to reduce or even prevent kidney stone formation. However, the evidence for these claims is not clear. We performed a study to assess the scientific evidence supporting commercially available dietary supplements for patients with urinary stone disease.
Methods: The online marketplace Amazon.com was queried for dietary supplements to treat, alleviate, or prevent stone disease. A Google search was similarly performed to capture products not available on Amazon. Product labels were reviewed to compile specific stone-related claims and non-pharmacological active ingredients (ie, excluding vitamins and ion salts) in each supplement. The cost of a 30-day course of recommended treatment was assessed. We queried Google Scholar with all non-pharmacological active ingredients to assess the scientific evidence from published and lay sources. Non-English studies and conference proceedings were excluded. Two investigators independently performed the searches and analysis.
Results: Of 113 products reviewed in the searches, 27 dietary supplements containing 56 non-pharmacological active ingredients were analyzed. Products made a variety of claims: 12 (44%) claimed to dissolve stones, 7 (26%) claimed to prevent stone formation, 6 (22%) claimed to reduce stone symptoms, and the majority (19, 70%) could be used to support kidney health. The mean 30-day cost was $32 (range $4-$189), and 10 (37%) products offered a money-back guarantee. Nearly all products were highly rated, with 21 products receiving â‰¥4 stars on a 5-star scale (mean 4.2, range 3.4-5.0). Of the 56 non-pharmacological ingredients, 9 (16%) had any published studies for use in stone disease, and 5 (9%) had exclusively studies supporting their use. A total of 18 scientific publications about the ingredients were identified, of which 6 showed mixed or no benefit for stone disease. In the other 12 publications supporting use in stone formers, only 5 were human studies. Overall, among the 27 supplements, 18 (67%) contained ingredients with conflicting, refuting, or absent evidence of benefit in stone disease.
Conclusions: In this analysis of commercially available dietary supplements claiming to treat or prevent kidney stones, two-thirds contained ingredients with conflicting or no scientific evidence to support their claims. These findings may assist clinicians in counseling stone formers about the use of these unregulated products.