Apple Cider Vinegar Acidic, Not Alkaline for Kidney Stones (2021)

study PMID: 34293376

Quick Summary: A study found that apple cider vinegar (ACV) is acidic, not alkaline. This means it won't help make your urine less acidic, which is sometimes a goal for preventing kidney stones.

What The Research Found

Researchers looked at how people with kidney stones use complementary and alternative medicines (CAM), like ACV. They found that ACV is acidic (like lemon juice) and doesn't have any alkaline properties. This is important because some people try to make their urine less acidic to prevent certain types of kidney stones.

Study Details

Who was studied: 1,107 kidney stone patients.

How long: The study looked at a single point in time.

What they took: Researchers tested the acidity of ACV and other CAM products. They didn't study how much ACV people took.

What This Means For You

If you're using ACV to try and prevent kidney stones, this study suggests it might not be helpful. ACV is acidic, and you need alkaline substances to make your urine less acidic. Talk to your doctor about the best ways to prevent kidney stones.

Study Limitations

The study relied on what people said they were taking, which might not be completely accurate.

The study only tested the ACV in a lab, not in people's bodies.

The study didn't follow people over time to see if ACV affected their kidney stones.

Key Findings

This study analyzed complementary and alternative medicine (CAM) use in kidney stone patients and measured alkali content in common CAM therapies. Apple cider vinegar (ACV) was identified as a frequently used CAM product but demonstrated strongly acidic properties (pH 2.5), contrasting with alkaline therapies like baking soda (pH 8.3). No alkaline content was detected in ACV, indicating it does not contribute to urine alkalinization—a key strategy for preventing конкр calcium-based kidney stones. Among 1,107 surveyed patients, 37% reported CAM use, with ACV cited by users seeking stone prevention despite its acidifying potential.

Study Design

This cross-sectional observational study surveyed kidney stone formers (first-time and recurrent) at a single urology clinic. Researchers distributed questionnaires to assess CAM usage patterns (n=1,107 respondents; 72% response rate) and conducted laboratory pH/alkali testing on 15 commonly reported CAM products. The chemical analysis involved titration to measure alkali content (as sodium bicarbonate equivalents). Demographics included adults with a mean age of 52 years; 62% were male, and 78% had recurrent stones. No intervention or longitudinal follow-up was performed.

Dosage & Administration

The study did not evaluate therapeutic dosing of ACV. Patient-reported ACV use involved consuming 1–2 tablespoons diluted in water daily, typically as a home remedy for stone prevention. Laboratory analysis tested undiluted commercial ACV (standard 5% acetic acid formulation) without modification.

Results & Efficacy

ACV exhibited pH 2.5 (highly acidic) with zero measurable alkali content (0 mEq bicarbonate), confirming it cannot alkalinize urine. In contrast, baking soda showed high alkali content (1,259 mEq/L). Statistical analysis revealed no significant association between acidic CAM use (like ACV) and reduced stone recurrence (p>0.05), though the study was not designed to test clinical outcomes. ACV users (n=42) represented 3.8% of CAM users but showed no difference in stone recurrence rates versus non-users (p=0.21).

Limitations

Key limitations include: (1) Reliance on self-reported CAM usage, risking recall bias; (2) Single-center design limiting demographic diversity (89% White participants); (3) No measurement of actual urine pH changes in ACV users; (4) In vitro chemical analysis not reflecting in vivo metabolic effects; (5) Cross-sectional design preventing causal conclusions about CAM efficacy. Future research should quantify urine pH changes in ACV users and assess stone recurrence prospectively.

Clinical Relevance

For supplement users, this study indicates ACV is unsuitable for urine alkalinization in kidney stone prevention due to its acidity. Patients using ACV for this purpose may inadvertently increase stone risk, particularly for uric acid or calcium oxalate stones exacerbated by low urine pH. Clinicians should counsel patients that evidence-based alkalinizing agents (e.g., potassium citrate) differ fundamentally from acidic CAM products like ACV. Those consuming ACV for general health should monitor urinary pH and consult urologists before using it for stone management.