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Apple cider vinegar for kidney stones: a new trial finds lemon water and coconut water raise urine citrate

In a 20-person trial, a week of apple cider vinegar did not change urine citrate, a kidney stone marker. Lemon water and coconut water raised it.

Published October 2026

Short answer

Vinegar did not change urine in this small trial, which was too small to rule out an effect. Lemon water and coconut water raised citrate, a substance that helps keep stones from forming. Evidence grade C (Limited). One small crossover trial (20 adults, six on vinegar) of urine markers in people without stones; downgraded for small sample and surrogate outcomes.

Key takeaways

  • In 20 adults without kidney stones, a week of daily apple cider vinegar drink did not significantly change 24-hour urine citrate, pH or volume [1].
  • Lemon water raised urine citrate by about 168 mg a day and coconut water by about 274 mg a day, compared with the participants' own starting levels [1].
  • The trial recruited fewer people than planned, and only six drank the vinegar, so it cannot rule out a real effect [1].
  • A 2026 review of stone prevention found low-certainty evidence that more water, a diet with normal to high calcium and low protein and sodium, and alkali treatment may reduce stone recurrence [2].
  • Citrus drinks may cause minor side effects, and anyone with a history of stones should ask a doctor before changing what they drink [2].

What the study did

Researchers tested whether four drinks change the urine chemistry that matters for kidney stones. Twenty adults who had never formed stones were each randomly given two of the four drinks: apple cider vinegar, coconut water, lemon water or diet orange soda. Each person drank one serving a day for one week, waited two weeks, then drank the second drink for a week [1]. The vinegar drink was 30 mL of vinegar diluted to 1 litre with water. Six people drank vinegar, six coconut water, eight lemon water and six diet orange soda [1].

They collected urine for 24 hours before and after each week and looked at citrate, which helps keep stone-forming minerals dissolved, plus urine acidity (pH) and volume [1].

What it found

Apple cider vinegar did not significantly change any of the three measures [1]. Lemon water raised urinary citrate by 167.7 mg a day (95% confidence interval 16 to 319), and coconut water raised it by 273.8 mg a day (95% confidence interval 67.9 to 480). Urine pH and volume did not change significantly with any drink [1]. The trial reported no adverse effects [1].

How it fits

Drinking more fluid is the long-standing advice for stone prevention, and the 2026 systematic review of 31 studies found low-certainty evidence that increased water intake, a diet with normal to high calcium, low protein and low sodium, thiazide medicines, alkali treatment and allopurinol may reduce recurrence in people with calcium stones [2]. Citrus fits the alkali idea. In a 12-person crossover study, 2 litres a day of diet lemonade raised urine citrate and lowered the stone-forming potential of calcium oxalate, while regular lemonade did not raise citrate, and it came with 225 g of sugar a day [3]. A separate trial in 173 people who had had calcium oxalate stones removed found a lime-based supplement cut two-year recurrence to 14% from 45% on placebo [4]. That was a supplement rather than a drink, so it says little about lemon water. None of these studies tested vinegar against stones.

Limits

The authors say the trial missed its recruitment target by a wide margin and should be read as exploratory, so a real effect of vinegar may have gone undetected. Blinding was not done, and the people studied had no history of stones, so the results may not apply to those who do [1]. It measured urine markers for one week, not whether anyone developed stones. The 2026 review noted possibly more minor side effects with lemon juice [2]. The Apple Cider Vinegar topic page covers its safety notes. This article is not medical advice; people with a stone history should talk to their doctor.

Go deeper

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References

  1. Apple cider vinegar for prevention of urinary lithiasis (APUL): a randomized crossover trial.. Int Urol Nephrol, 2026.
  2. Prevention of Recurrent Nephrolithiasis in Adults and Children : A Systematic Review.. Ann Intern Med, 2026.
  3. The Effect of Lemonade and Diet Lemonade Upon Urinary Parameters Affecting Calcium Urinary Stone Formation.. J Endourol, 2019.
  4. Lime-based supplement reduces calcium oxalate stone recurrence: A multicenter randomized controlled trial.. PLoS One, 2025.