Diet for kidney stone prevention

The core dietary pattern

For the large majority of patients (mostly calcium stone formers) the recommended pattern is:^{1, 2}

• High fluid - urine output of 2.5 L a day (see hydration).
• Normal calcium - about 1,000-1,200 mg a day, from food rather than supplements where possible, and spread across meals.
• Low sodium - less than about 2,300 mg/day (roughly one teaspoon of salt), including hidden sodium in processed and takeaway foods.
• Moderate animal protein - about 0.8-1.0 g/kg/day (for many adults, around a single palm-sized portion of meat or fish a day).
• Modest oxalate - avoid extreme intakes (very large servings of spinach, rhubarb, beetroot, certain nuts, strong tea) but do not attempt a strict oxalate-free diet.
• Plenty of fruit and vegetables - natural sources of citrate and potassium.

Why "low calcium" is the wrong advice

Counter-intuitively, a low-calcium diet increases the risk of calcium oxalate stones. This is because dietary calcium normally binds oxalate in the gut so that it is passed in the stool rather than absorbed. With less calcium in the meal, more oxalate is absorbed, more appears in the urine, and stones are more likely to form.¹ A classic randomised trial (Borghi et al.) showed this directly - a normal-calcium, low-sodium, low-protein diet halved the recurrence rate compared with a low-calcium diet.

Sodium - the hidden driver

Dietary sodium is the main driver of urinary calcium. Every excess gram of sodium leads to a rise in urinary calcium excretion, which is why a low-sodium diet is consistently effective for calcium stone formers.¹ Practical steps:

• Reduce added salt in cooking and at the table.
• Read labels - processed foods often have very high sodium content.
• Limit takeaway and commercially-prepared meals.
• Be cautious with salty condiments - soy sauce, fish sauce, stock cubes.

Animal protein

High intakes of red meat, poultry, and fish increase urinary calcium and uric acid and reduce urinary citrate - all of which favour stone formation. Moderation rather than vegetarianism is the aim:¹

• One palm-sized portion a day is a reasonable target for most adults.
• Plant-based protein sources (legumes, tofu, dairy) are a good alternative.
• Uric acid stone formers benefit most from reducing animal protein, particularly organ meats and shellfish.

Oxalate - sensible, not extreme

Oxalate is found in many healthy foods. An oxalate-free diet is neither possible nor necessary. What is sensible:

• Avoid very large daily intakes of spinach, rhubarb, beetroot, chocolate, nuts, and strong black tea.
• Eat oxalate-rich foods with a calcium-containing food (a handful of nuts with yoghurt; spinach with cheese) so that oxalate is bound in the gut.
• Keep dietary calcium adequate - this is the best oxalate strategy.

Citrate - the natural inhibitor

Citrate in the urine inhibits calcium crystal formation and is a marker of a stone-friendly diet. Dietary citrate comes mostly from fruit and vegetables, particularly citrus fruits.

• Include citrus fruits or diluted fresh lemon or lime juice in daily fluid.
• Evidence from randomised trials on citrus juices is modest but the mechanism is clear.³
• For patients with persistently low urinary citrate, prescription potassium citrate is better evidenced.

Diet tailored to stone type

Calcium oxalate

The core pattern above. Attention to sodium, protein, and normal dietary calcium.

Calcium phosphate

Same core pattern. Because these stones form in alkaline urine, extremely high citrate intake may be counter-productive; individualised advice from a renal physician is useful.

Uric acid

Reduce purine-rich foods (red meat, offal, shellfish, anchovies, sardines). Weight reduction if obese. Ample fluid. Urinary alkalinisation with potassium citrate is central - see the uric acid stones page.

Struvite

Diet is less central - the driver is persistent urinary infection. Strategy is to eradicate infection and remove all stone material. See the struvite stones page.

Cystine

Very high fluid intake, modest animal protein, moderate sodium, and alkalinisation with potassium citrate. Specialist metabolic clinic input is essential. See the cystine stones page.

Working with a dietitian

For recurrent stone formers, a single appointment with a renal-trained dietitian is often more useful than any general pamphlet. The 24-hour urine results guide which of the levers - calcium, sodium, protein, oxalate, citrate, fluid - most need pulling for you individually. Dr Kooner's metabolic pathway includes access to experienced dietitians through partner renal physician clinics.

Patient brochure

Dietary advice for recurrent stone formers PDF - BAUS patient brochure

Related pages

References

1. Skolarikos A, et al. EAU Guidelines on Urolithiasis. 2025.
2. Qaseem A, et al. Dietary and pharmacologic management to prevent recurrent nephrolithiasis: a systematic review. Annals of Internal Medicine. 2026.
3. Nabi R, et al. Citrus juice in reducing calcium kidney stone risk. African Journal of Urology. 2025;31:70.