Patient Perceptions of Dietary Supplement Use and Kidney Stone Disease

~20% of kidney stone patients use cranberry extract or ACV; 87% believe them safe, almost none heard about them from a physician

Journal: Nutrients | Published: 2026-05-07 | Type: Cross-sectional survey | PMID: 42196941 Authors: Kim DD, Prochaska ML, Weiss A, Zisman AL, Worcester EM, Reynolds LF (University of Chicago Medical Center, urology and nephrology) Funding/COI: NIH HHS. No conflicts of interest declared.

Summary

A survey of 95 kidney stone patients at a single academic center found substantial use of apple cider vinegar, cranberry extract, and turmeric — three supplements with no established benefit and some potential for harm in stone disease. The vast majority believed these supplements to be safe, and they got that impression primarily from friends, the internet, and social media rather than their clinicians. The evidence base for any of these supplements in stone prevention is either absent or actively conflicting.

Claims

• 18.9% of patients reported using ACV, 20% reported using cranberry extract, 11.6% reported using turmeric
• 87.4% believed ACV to be "probably" or "definitely" safe; 94.8% believed cranberry extract safe; 87.4% believed turmeric safe
• Top information sources: friends/family (26.3%), online websites (22.1%), social media (15.8%)
• Only 11.6% reported receiving supplement information from a physician or healthcare professional
• 41.1% had never heard of these supplements being used for kidney stones at all — yet many of them still used them
• 62.1% of the cohort were recurrent stone formers; median age 64; 57.9% female; 47.4% identified as Black or African American

Study Quality

This is a descriptive cross-sectional survey of 100 patients at a single institution (5 excluded for reporting multiple racial identities, leaving n=95). The study uses only descriptive statistics — frequencies and proportions — with no inferential analysis. There is no comparison group, no longitudinal follow-up, and no data on stone type, dietary habits, or clinical outcomes. Surveys were paper-based, administered in English only, and conducted in-person at outpatient clinic visits, which introduces selection bias toward patients engaged enough in their care to show up for consultations. The survey instrument was developed with institutional support and IRB-approved, which is appropriate, but not validated against any external measure.

The study is honest about what it is: exploratory, descriptive, hypothesis-generating. It makes no causal claims. The analysis matches the design.

Red Flags

• n=95 at a single academic center in Chicago — findings may not generalize to other regions, demographics, or practice settings
• English-only surveys exclude non-English-speaking patients, a meaningful gap in a diverse urban cohort
• No data on which stone type patients had (calcium oxalate, uric acid, struvite) — critical context given that cranberry juice is specifically implicated in oxalate stone formation
• No data on dose, frequency, or duration of supplement use
• "Heard of" and "used" are conflated in some places in the analysis; the paper does not report what fraction used supplements specifically believing they helped with stones
• Five patients excluded for reporting multiple racial identities — unusual exclusion criterion that deserves more explanation

Strengths

• Fills a genuine gap: supplement use in stone patients is common but understudied
• IRB-approved, prospectively designed survey with standardized instrument
• Racially diverse cohort (47.4% Black/African American) — unusual for a stone disease study, which historically skews White
• Accurately characterizes the evidence on ACV, cranberry, and turmeric: either absent or conflicting, with turmeric's high oxalate content flagged as a specific lithogenic risk
• No overreach in conclusions — the paper correctly calls for further research rather than making efficacy claims

Verdict

This is a small, single-site, descriptive survey — no hypothesis testing, no outcomes data. By strict methodological standards, it proves nothing. What it does do is document a concrete, clinician-relevant problem: patients with recurrent kidney stones are regularly using supplements with unknown or potentially harmful effects on stone pathophysiology, they overwhelmingly believe these supplements are safe, and they are getting this belief from social media rather than the physicians treating them. The paper's value is situational awareness, not evidence synthesis. Worth two minutes of your attention if you treat stone patients; not worth citing in a clinical guideline.