Kidney Stones Diet — What to Eat & Avoid

Calcium oxalate stones (80%): focus on fluids, normal calcium, low oxalate, low sodium, normal protein. Calcium phosphate stones (10–15%): similar but also watch alkali load and consider thiazide diuretics if recurrent. Uric acid stones (5–10%): reduce purines (red meat, offal, shellfish, anchovies), limit alcohol especially beer, and alkalinise urine with fruit/vegetables. Cystine stones (1–2%): very high fluid intake (aim for 3–4 litres urine output), urine alkalinisation, and specialist care. Struvite stones (infection-related): treat the underlying urinary tract infection — diet plays a smaller role.

Diluting urine is the cornerstone of stone prevention. Aim for 2.5–3 litres of urine output daily, which usually means drinking 2.5–3.5 litres of fluid depending on climate and activity. Water is best. Citrus-flavoured water adds citrate. Tea and coffee count but watch oxalate in black tea. Limit sugar-sweetened drinks. Spread intake through the day — a jug-based routine helps.

When you eat less calcium, more oxalate is absorbed from the gut into the blood, then excreted in urine — raising oxalate concentration and stone risk. Normal dietary calcium (700–1,000 mg/day from milk, yoghurt, cheese, fortified alternatives, tinned fish with bones) should be maintained. Pair high-oxalate foods with calcium at the same meal — for example, a small amount of cheese with a spinach-containing dish. Calcium supplements taken without meals can spike urinary calcium — avoid unless prescribed and always take with food.

You do not need a zero-oxalate diet. The goal is to avoid very high-oxalate foods in large amounts. Spinach is the highest-oxalate food commonly eaten — a spinach smoothie can deliver more oxalate than a sensible day's limit. Beetroot, rhubarb, almonds, dark chocolate (70%+ cocoa), wheat bran, soy flour, and black tea are also significant. Lower-oxalate alternatives: cauliflower, cabbage, cucumber, grapes, apples, pears, white rice, and pasta.

High sodium (salt) increases calcium in urine. Most UK adults eat 8–9 g salt per day — nearly double the recommended maximum. Processed and restaurant foods are the main sources. Animal protein in large amounts increases uric acid and reduces citrate in urine. Aim for moderate portions: a palm-sized serving of meat/fish/poultry per meal, not steak-house portions. Plant proteins (beans, lentils, tofu) have a lower stone risk profile.

All first-time stone formers should have stone analysis and basic blood tests. Recurrent stone formers (more than one stone) should have 24-hour urine testing for calcium, oxalate, citrate, uric acid, sodium, and volume. A nephrologist or urologist can then tailor diet and medication — for example, thiazide diuretics for hypercalciuria, potassium citrate for hypocitraturia, or allopurinol for hyperuricosuria.