Does a low-sodium diet prevent kidney stones?

Possibly, for people who already make calcium stones, though nobody has tested salt on its own. In a five year randomized trial of 120 men with repeat calcium oxalate stones and too much calcium in their urine, 12 of 60 on a diet with normal calcium, less animal protein and less salt had another stone, against 23 of 60 on a low calcium diet. Salt was one of three changes in that diet, so the trial cannot tell how much of the benefit came from salt.

Unsettled. A meta-analysis of eight randomized trials in 1855 people with past stones found no trial that tested the independent effect of changing dietary sodium on stone recurrence. The newest review, done for the American College of Physicians and covering 26 randomized trials and 5 other studies, says a diet with normal to high calcium, low protein and low sodium may prevent repeat stones, with low strength of evidence. That is where the question stands.

Men who had another stone, out of 60 in each group

Raw counts from one randomized trial in men with recurrent calcium oxalate stones and high urine calcium, so no interval is drawn. The first diet changed salt, animal protein and calcium at the same time. Source: card ev-nakst-06 below.

What the trials found

The five year trial is the only one with stones as the result. The diet gave each man 30 mmol of calcium, 52 g of animal protein and 50 mmol of sodium chloride a day, and it was compared with a low calcium diet rather than with ordinary eating. A Cochrane review counted the same trial by new stones instead of by men who relapsed and got a risk ratio of 0.77, with an interval from 0.61 to 0.98. The Cochrane authors also note that the methods of the trials they reviewed were poorly reported.

Kidney stone risk, relative to the comparison group

Diet trialObservational data

Below 1 means fewer stones. The two trial rows come from the same trial in people who already had stones, measured two ways, and the diet changed more than salt. The observational row is about a first stone and cannot show cause. Sources: cards ev-nakst-01, 06 and 08 below.

A second trial looked at salt alone, over three months, in 210 people with calcium stones and high urine calcium. On the low salt diet urine calcium came back into the normal range in 61.9 percent of patients, against 34.0 percent on the control diet, a difference of 27.9 points with an interval from 14.4 to 41.3. Pooled by Cochrane, the low salt diet cut urinary calcium by 45 mg a day and urinary oxalate by 4 mg a day. Both are urine measurements that predict stones. Nobody counted stones in that trial, and three months is short.

A 2021 meta-analysis of six randomized trials went further and called the effect of a low sodium, normal calcium diet marked. That conclusion rests on the same single five year trial, so it is stronger than the data behind it.

Preventing a first stone

For people who have never had a stone there are only observational data. Pooled across 50 studies and 1.3 million people, those eating the most sodium had a 38 percent higher risk of a first kidney stone, with a relative risk of 1.38 and an interval from 1.21 to 1.56. Sodium in those studies was mostly estimated from questionnaires, and people who eat more salt differ in other ways. An umbrella review of 17 meta-analyses graded dietary sodium as a suggestive causal risk factor. A Mendelian randomization study in FinnGen and UK Biobank found that genes linked to higher urinary sodium may also raise stone risk, and its abstract gives no size for that effect.

Who should be careful

Not for everyone. Swapping table salt for a potassium salt substitute is a common way to cut sodium, and it is the wrong one for some stone formers. The WHO recommendation for these substitutes excludes people with kidney impairment and people taking potassium-sparing diuretics or potassium supplements. It is also not meant for children or pregnant women.

An Italian urology guideline adds a caution for older stone formers. Cutting sodium is still advised, together with more potassium, magnesium and citrate, but older people react more strongly to sodium in their blood pressure and often have lower kidney function, and both need to be taken into account. The guideline gives no numbers for this. If you already have kidney disease or take a diuretic, how far to cut salt is a question for the person treating you.

What expert bodies say

The same Italian working group advises moderate salt restriction to limit urinary calcium, for preventing a first stone and a repeat one, and in children too. It is an expert guideline, and the evidence behind it is low, especially for children. WHO recommends that adults eat less than 2 g of sodium a day, which is 5 g of salt. The US Institute of Medicine set the tolerable upper intake level at 2,300 mg of sodium a day for people aged 14 and over. Both limits were set for blood pressure and the heart, not for stones. They are general limits, not a target tested in stone formers.

For where sodium comes from in food, see salt.

How we searched

Searched: a local copy of the PubMed 2026 baseline, for sodium or salt with kidney stones, nephrolithiasis, urinary calcium and hypercalciuria. The broad query returned 959 records and we screened the top 40. A narrower query for low salt trials in stone formers returned 27, and a query for sodium and urinary calcium in trials and meta-analyses returned 168, of which we screened the top 20. We also searched the WHO guideline layer, an AHRQ evidence report, ClinicalTrials.gov and the open web. Search run on 7 October 2026.

Included: four systematic reviews and meta-analyses of randomized trials, two randomized trials, an observational meta-analysis, an umbrella review, a Mendelian randomization study, an Italian urology guideline and two WHO guidelines. None of the sources has been retracted.

Excluded: a second Mendelian randomization study where the urinary sodium signal held in only one dataset, trials where sodium was not the intervention or stones were not the outcome, and a cross-sectional survey. The 2026 American Urological Association guideline and the European urology guidelines also advise less sodium, but their sites are outside our list of trusted sources, so we did not cite them.

What we read: abstracts for most sources, and the full results sections of two meta-analyses from PubMed Central.

What we could not get: the full texts of the 2026 American College of Physicians review and of both randomized trials. Their abstracts are what this page quotes.

What would change this answer

A randomized trial that cuts salt and nothing else, with new stones as the result. We found none registered in our copy of ClinicalTrials.gov.
A trial in women. The only trial that counted stones recruited men.
A trial that compares a low salt diet with ordinary eating. The five year trial compared it with a low calcium diet, which is itself a poor diet for stone formers.
Trial evidence for preventing a first stone. Today that part of the answer rests on observational data alone.

The rest of the nutrient, in one place. Sodium: what lowering it actually does to blood pressure and to death rates → What it does, how much you need, who runs short, and what too much does, with the evidence level shown on every line.

The food behind this question

Pink salt, sea salt and the iodine you lose — numbers, evidence and safety

The full guide

Sodium: what lowering it actually does to blood pressure and to death rates

The same question for other foods (kidney stones)

Sources

ev-nakst-01 · Meta-analysis or systematic review · Cochrane systematic review of RCTs (data not pooled) · n = 120 participants (1 study); review 5 studies, 379 adults
One study (120 participants) compared a low calcium diet with a normal calcium, low protein, low salt diet for five years. There was a significant decrease in numbers of new stone recurrences in those treated with the normal calcium, low protein, low salt diet (RR 0.77, 95% CI 0.61 to 0.98).
Who: adults with idiopathic hypercalciuria and recurrent calcium stones
Effect: RR 0.77 (95% CI 0.61 to 0.98) for new stone recurrences, normal calcium + low protein + low salt vs low calcium diet
Certainty: Salt here is only one of three components; the isolated effect of salt cannot be separated. The methodology of the studies is poorly described (Cochrane).
Cochrane Database Syst Rev, 2014 · checked 2026-10-07 · we read the abstract
ev-nakst-02 · Meta-analysis or systematic review · Cochrane systematic review of RCTs · n = 210
One study (210 participants) compared a low salt, normal calcium diet with a broad diet for three months. The low salt, normal calcium diet decreased urinary calcium (MD -45.00 mg/d, 95% CI -74.83 to -15.17) and oxalate excretion (MD -4.00 mg/d, 95% CI -6.44 to -1.56).
Who: calcium stone formers with idiopathic hypercalciuria
Effect: urinary calcium MD -45.00 mg/d (95% CI -74.83 to -15.17); oxalate MD -4.00 mg/d (95% CI -6.44 to -1.56)
Certainty: Surrogate endpoints (urine), not the number of stones; 3 months.
Cochrane Database Syst Rev, 2014 · checked 2026-10-07 · we read the abstract
ev-nakst-03 · Meta-analysis or systematic review · systematic review of RCTs and nonrandomized studies (AHRQ/PCORI) · n = 31 studies (26 RCTs, 5 NRSIs)
Increased fluid intake; a diet with normal to high calcium, low protein, and low sodium; thiazides; alkali therapy; and allopurinol may prevent stone recurrence in adults with calcium oxalate or calcium phosphate stones.
Who: adults with calcium oxalate or calcium phosphate stones
Effect: may prevent stone recurrence (low strength of evidence); no separate effect size for sodium
Certainty: The newest synthesis (search to December 2025). Low SOE; salt again only as part of a diet.
Ann Intern Med, 2026 · checked 2026-10-07 · we read the abstract
ev-nakst-04 · Meta-analysis or systematic review · systematic review and meta-analysis of RCTs · n = 8 trials, 1855 participants
No trials examined the independent effect of altering dietary calcium, sodium, animal protein, fruit and fiber, purine, oxalate, or potassium.
Who: adults with a history of nephrolithiasis
Effect: no trial isolated sodium; multicomponent diet with low sodium: recurrence 20% vs 38% (p=0.03)
Certainty: Search up to 2008, but ACP 2026 likewise has no isolated RCT on salt.
Eur Urol, 2009 · checked 2026-10-07 · we read the abstract
ev-nakst-05 · Meta-analysis or systematic review · systematic review and meta-analysis of RCTs · n = 6 RCTs
In conclusion, our study shows that the only low protein with or without fiber does not affect recurrence, but low Na, normal Ca diet has a marked effect on reducing recurrence of calcium stone.
Who: patients with recurrent calcium stones
Effect: low protein with or without fiber alone: RR 2.32 (95% CI 0.42 to 12.85); benefit attributed to low Na plus normal Ca diet (one trial)
Certainty: The conclusion on salt rests on one RCT (Borghi 2002), so "marked effect" is stronger than the data allow.
PLoS One, 2021 · checked 2026-10-07 · we read the abstract
ev-nakst-06 · Randomized controlled trial(s) · randomized controlled trial, 5 years · n = 120
At five years, 12 of the 60 men on the normal-calcium, low-animal-protein, low-salt diet and 23 of the 60 men on the low-calcium diet had had relapses.
Who: men with recurrent calcium oxalate stones and hypercalciuria; diet with 30 mmol calcium, 52 g animal protein and 50 mmol sodium chloride per day
Effect: unadjusted RR 0.49 (95% CI 0.24 to 0.98; P=0.04) for recurrence over 5 years
Certainty: Men only; comparison with a low-calcium diet, not with a usual diet; three changes together.
N Engl J Med, 2002 · checked 2026-10-07 · we read the abstract
ev-nakst-07 · Randomized controlled trial(s) · randomized controlled trial, 3 months · n = 210
Urinary calcium was within the normal range in 61.9% of the patients on the low-salt diet and in 34.0% of those on the control diet (difference: +27.9%; 95% CI: +14.4%, +41.3%; P < 0.001).
Who: patients with idiopathic calcium stone disease and hypercalciuria (>300 mg Ca/d in men, >250 mg Ca/d in women)
Effect: urinary sodium 228 to 68 mmol/d; normal urinary calcium in 61.9% vs 34.0% (difference +27.9%, 95% CI +14.4% to +41.3%)
Certainty: The endpoint is urinary calcium, not stones. 11 of 108 in the diet group dropped out.
Am J Clin Nutr, 2010 · checked 2026-10-07 · we read the abstract
ev-nakst-08 · Observational data · systematic review and meta-analysis of observational studies · n = 50 articles, 1,322,133 participants, 21,030 cases
Prominent risk factors for incident stones were body mass index (1.39,1.27-1.52), dietary sodium (1.38, 1.21-1.56), fructose, meat, animal protein, and soda.
Who: adults without stones at baseline, prospective cohorts and RCTs
Effect: dietary sodium RR 1.38 (95% CI 1.21 to 1.56), highest vs lowest intake
Certainty: Observational data, confounding and sodium estimated by questionnaires; primary prevention, not recurrence.
BMC Nephrol, 2020 · checked 2026-10-07 · we read the abstract
ev-nakst-09 · Observational data · umbrella review of meta-analyses (AMSTAR 2, GRADE) · n = 17 meta-analyses, 46 risk factors
The authors' study demonstrates the suggestive causal (central obesity, type 2 diabetes, gout, dietary sodium, fructose intake and higher temperatures) risk factors of nephrolithiasis.
Who: meta-analyses of risk factors for nephrolithiasis
Effect: dietary sodium: suggestive (GRADE) positive association
Certainty: Synthesis mostly of observational meta-analyses.
Int J Surg, 2024 · checked 2026-10-07 · we read the abstract
ev-nakst-10 · Observational data · two-sample Mendelian randomization with meta-analysis · n = 44 modifiable risk factors tested
The combined results indicated that previous exposures may increase the risk of kidney stones, including sedentary behavior, urinary sodium, the urinary sodium/potassium ratio, the urinary sodium/creatinine ratio, serum calcium, 25-hydroxyvitamin D (25OHD), the estimated creatinine-based glomerular filtration rate (eGFRcrea), GFR estimated by serum cystatin C (eGFRcys), body mass index (BMI), waist circumference, type 2 diabetes mellitus (T2DM), fasting insulin, glycated hemoglobin, and hypertension.
Who: FinnGen discovery and UK Biobank validation datasets
Effect: urinary sodium and urinary sodium/potassium ratio associated with higher risk; size not in the abstract
Certainty: Genetic proxies of urinary sodium; pleiotropy is possible. The effect size is not given in the abstract.
Front Endocrinol (Lausanne), 2023 · checked 2026-10-07 · we read the abstract
ev-nakst-11 · Position of an expert body · society guideline based on a systematic search (CLU Working Group) · n = —
Moderate dietary salt restriction is useful in limiting urinary calcium excretion and thus may be helpful for primary and secondary prevention of nephrolithiasis.
Who: stone formers with hypercalciuria; children with nephrolithiasis
Effect: moderate dietary salt restriction recommended
Certainty: Expert guideline; the level of evidence is low, especially for children.
Arch Ital Urol Androl, 2015 · checked 2026-10-07 · we read the abstract
ev-nakst-12 · Position of an expert body · society guideline (CLU Working Group) · n = —
A restriction of sodium intake in association with a higher intake of potassium, magnesium and citrate is advisable in order to reduce urinary risk factors for stone formation but also to prevent the loss of bone mass and the incidence of hypertension, although more hemodynamic sensitivity to sodium intake and decreased renal function of the elderly have to be considered.
Who: elderly stone formers
Effect: restrict sodium with more potassium, magnesium and citrate, adjusted for age-related sodium sensitivity and renal function
Certainty: Advice without quantitative limits.
Arch Ital Urol Androl, 2015 · checked 2026-10-07 · we read the abstract
ev-nakst-13 · Position of an expert body · WHO guideline (GRADE) · n = —
The recommendation in this guideline is intended for adults in the general population and excludes individuals with kidney impairments or with other circumstances or conditions that might compromise potassium excretion (e.g. those taking potassium-sparing diuretics and potassium supplements).
Who: adults in the general population; excludes kidney impairment, potassium-sparing diuretics, potassium supplements, children, pregnant women
Effect: conditional recommendation for lower-sodium salt substitutes, with exclusions
Certainty: Important for people with stones and CKD who replace salt with potassium salt.
WHO, 2025, Use of lower-sodium salt substitutes: WHO guideline summary · checked 2026-10-07 · we read the section
ev-nakst-14 · Position of an expert body · WHO guideline (NUGAG, GRADE) · n = —
WHO recommends a reduction to <2 g/day sodium (5 g/day salt) in adults (strong recommendation).
Who: adults
Effect: <2 g/day sodium (5 g/day salt), strong recommendation
Certainty: The norm is set for blood pressure and cardiovascular events, not for stones.
WHO, 2012, Guideline: sodium intake for adults and children · checked 2026-10-07 · we read the section
ev-nakst-15 · Position of an expert body · government evidence report citing IOM DRI · n = —
The IOM set the UL for sodium at 2,300 mg per day for people aged 14 years and over, with lower values for those 1-13 years of age.
Who: people aged 14 years and over
Effect: UL 2,300 mg/day sodium; AI 1,500 mg/day (ages 19-50)
Certainty: Since 2019 NASEM replaced the UL with a CDRR of 2300 mg with the same number.
AHRQ, 2018, Sodium and Potassium Intake: Effects on Chronic Disease Outcomes and Risks · checked 2026-10-07 · we read the section

How this page was made. Evidence was extracted from primary sources into cards, every number was re-checked against the source, and the text was written from those cards. Bioma Learn has no human medical reviewer at this time, and we say so rather than invent one. Methodology. This is information, not medical advice.