What Causes Kidney Stones, and How Can Diet Help Prevent Them?

Once you have had a kidney stone, the condition tends to come back. Breaking up or passing the stone solves the immediate problem, but if the conditions that led to the stone do not change, new stones can form. In this article we explain why kidney stones form and what you can pay attention to in your daily diet.

How do kidney stones form?

Urine naturally contains dissolved substances such as calcium, oxalate, uric acid and phosphate. When urine becomes too concentrated, or when the substances that prevent stone formation (such as citrate) are reduced, these substances form crystals. Over time, the crystals join together and turn into a stone.

The most common type is the calcium oxalate stone. Uric acid, calcium phosphate, infection (struvite) and cystine stones are also seen. The type of stone directly determines which measures should be taken.

What causes kidney stones?

Usually several factors come together in stone formation:

• Drinking too little: This is the most important risk factor that can be changed. The more concentrated the urine, the more easily crystals form.
• Hot climate and heavy sweating: Fluid loss increases in summer, during heavy physical work and during sport.
• Too much salt: Salt increases the amount of calcium passed in the urine.
• Too much animal protein: Red meat, offal and processed meats increase uric acid and lower citrate.
• Obesity, diabetes and metabolic syndrome.
• Gout and high blood uric acid levels.
• Family tendency: The risk is higher in people with a family history of stones.
• Recurrent urinary tract infections: Certain bacteria pave the way for infection stones.
• Anatomical causes such as narrowings in the kidney and urinary tract.
• Diseases of the parathyroid glands and certain bowel diseases.
• Certain medicines and high-dose vitamin C supplements.

Who gets kidney stones more often?

They are more common in men than in women and mostly appear in middle age. Because of its hot climate and dietary habits, Turkey is one of the regions where stone disease is common. Having passed a stone before is one of the strongest predictors of a new stone.

How should you eat to prevent kidney stones?

The general advice below applies to most patients with calcium oxalate stones. If your stone type is known, the advice is tailored accordingly.

1. Drink more. Drink about 2.5–3 litres of fluid, spread throughout the day. The aim is pale urine. Drink more in hot weather and when you sweat.
2. Cut down on salt. Not putting a salt cellar on the table and limiting pickles, brined foods, crisps, processed meats and ready meals is an effective start.
3. Eat animal protein in moderation. Cut down on red meat, offal and processed meats and have more vegetable-based meals.
4. Do not cut out calcium. Getting a normal amount of calcium from foods such as milk, yoghurt and cheese can lower the risk of stones.
5. Be moderate with oxalate-rich foods. Spinach, chard, cocoa, chocolate, nuts and very strong tea contain oxalate. Rather than banning them completely, it is enough not to overdo them.
6. Eat more fruit and vegetables. Citrus fruits in particular are rich in citrate, which helps prevent stones.
7. Limit sugary and fizzy drinks. Drinks containing fructose can increase the risk of stones.
8. Keep your weight under control.

Does the diet depend on the type of stone?

Yes. The advice above applies to the most common calcium oxalate stones; other types of stone need additional measures:

• Uric acid stones: Red meat, offal, some fish such as anchovies and sardines, alcohol and especially beer are limited. These stones can often be dissolved with medicines that make the urine less acidic.
• Infection (struvite) stones: The main goal is to clear the stone completely and to prevent urinary tract infections.
• Cystine stones: These are due to an inherited condition; a much higher fluid intake and special medication may be needed.

For this reason, rather than following general diet lists from the internet, it is better to follow advice based on the analysis of your own stone.

What are the common myths about kidney stones?

• “Calcium-rich foods cause stones.” On the contrary, calcium from food can be protective by binding oxalate in the gut.
• “Beer helps you pass stones.” Alcohol dehydrates the body; water is always the better choice.
• “Hard water causes stones.” What matters is the amount of water, not the type.
• “The stone has passed, so there is no problem any more.” Stone disease can recur. Having the passed stone analysed guides the next steps in prevention.
• “Herbal teas dissolve stones.” Apart from uric acid stones, it is generally not possible to dissolve stones with medicines or herbs. Herbal mixtures taken without guidance can harm the kidneys.

Why are stone analysis and metabolic assessment important?

Laboratory analysis of a stone that has been passed or removed surgically shows what type of stone it is. For patients who pass stones frequently, who had stones as a child, or who have stones on both sides or large stones, a metabolic assessment with blood tests and a 24-hour urine collection is recommended. This allows dietary advice and, if necessary, medication to be tailored to the individual.

For treatment options for an existing stone, see the kidney stone treatment and laser kidney stone surgery (RIRS) pages.

When should you see a urologist?

See a urologist if you have pain spreading from your back to your groin, blood in your urine, or frequent and burning urination, or if you have passed a stone before. If stone pain comes with fever and shivering, or the amount of urine you pass has dropped noticeably, go to the emergency department without waiting.

Op. Dr. Mücahit Kabar sees patients in Bursa (Nilüfer), Turkey, at Özel Medicabil Nilüfer Hastanesi (weekdays 08:30–12:00, +90 444 8 112) and Özel Jimer Hastanesi (weekdays 13:00–17:00, +90 444 45 67). Appointments are booked through the hospitals’ online booking pages or appointment lines. Consultations are held in English or Turkish; the hospitals’ international patient departments can arrange interpreters for other languages. For questions or to share reports and scans before your visit, you can send a WhatsApp message to +90 541 622 54 82. Further details are on the contact page.