How Do Kidney Stones Form?

Kidney stones are hard deposits formed when minerals and salts in the urine-such as calcium, oxalate, uric acid, phosphate, or cystine-crystallize and accumulate.

Approximately 80% of kidney stones contain calcium, primarily in the form of calcium oxalate or calcium phosphate. The remaining 20% include uric acid stones, infection-related stones (struvite stones), and cystine stones caused by inherited metabolic disorders.

According to experts, kidney stones develop when urine becomes highly concentrated, increasing the concentration of stone-forming substances. Over time, microscopic crystals stick together, forming stone nuclei that gradually enlarge. This process is more likely to occur when the body lacks natural inhibitors of crystal formation, such as citrate and magnesium.

Common Causes of Kidney Stones

Inadequate Water Intake

Insufficient hydration is considered the most important dietary risk factor for kidney stone formation.

When the body does not receive enough fluids, urine volume decreases and becomes more concentrated. As mineral concentrations rise, crystals form more easily and eventually develop into stones.

Excessive Salt Consumption

A diet high in salt, fish sauce, processed foods, canned products, pickled foods, and instant noodles can significantly increase the risk of kidney stones.

Excess sodium causes the kidneys to excrete more calcium into the urine. When calcium combines with oxalate or phosphate, stone formation becomes more likely.

Excessive Animal Protein Intake

Frequent consumption of red meat, organ meats, and purine-rich seafood increases uric acid levels in the urine and makes the urinary environment more acidic.

These conditions promote the formation of uric acid stones and increase the risk of calcium oxalate stones.

Imbalance Between Calcium and Oxalate

Many people regularly consume foods rich in oxalate, including spinach, asparagus, chocolate, nuts, and strong tea.

Conversely, some individuals with kidney stones avoid dairy products and other calcium-rich foods out of concern that calcium may worsen their condition. This is a common misconception.

Insufficient dietary calcium actually increases oxalate absorption from the intestine into the bloodstream, leading to higher oxalate levels in the urine and a greater risk of recurrent stone formation.

Excessive Use of Vitamin C and Vitamin D

Long-term use of high-dose vitamin C supplements (more than 1,000 mg per day) may increase urinary oxalate levels.

Similarly, excessive vitamin D supplementation can enhance calcium absorption and indirectly contribute to kidney stone formation.

Associated Medical Conditions

People with gout, recurrent urinary tract infections, or a family history of kidney stones are also at higher risk.

Dietary Recommendations for Preventing Kidney Stones

Drink Enough Water Every Day

Adequate hydration is the simplest and most effective preventive measure.

Adults should consume approximately 2.5–3 liters of fluids daily to maintain a urine output of at least 2 liters per day.

Plain water should be the primary choice. Fresh lemon or orange juice may also be beneficial because they contain citrate, a natural compound that helps inhibit stone formation.

Limit Salt Intake

Daily sodium intake should remain below 2,000 mg, equivalent to approximately one teaspoon of salt.

It is advisable to reduce the consumption of dipping sauces, processed foods, canned products, pickled foods, fermented shrimp paste, and instant noodles.

Maintain Adequate Calcium Intake

Adults should consume approximately 800–1,200 mg of calcium daily from natural food sources such as milk, yogurt, cheese, and small fish eaten with their bones.

Dietary calcium binds to oxalate in the intestines, reducing oxalate absorption and protecting the kidneys from excess oxalate exposure.

Moderate Animal Protein Consumption

Red meat, organ meats, and purine-rich seafood should be consumed in moderation.

Replacing part of the animal protein intake with plant-based proteins from beans and legumes may help maintain a healthier urinary environment.

Limit High-Oxalate Foods

Foods that should be consumed in moderation include spinach, asparagus, chocolate, strong tea, almonds, cashews, and peanuts.

When consuming these foods, pairing them with calcium-rich foods may help reduce oxalate absorption.

Vegetables such as cabbage, broccoli, cauliflower, chayote squash, and green peas, along with fruits such as pears and plums, are generally better choices.

Increase Potassium- and Magnesium-Rich Foods

Bananas, avocados, dragon fruit, and green leafy vegetables are excellent sources of potassium and magnesium.

These minerals help reduce urinary calcium excretion and inhibit crystal formation.

Avoid Unnecessary High-Dose Vitamin C Supplementation

People should avoid prolonged use of high-dose vitamin C supplements unless prescribed or recommended by a healthcare professional.

Personalized Nutrition Is Key to Preventing Recurrence

Experts emphasize that there is no single diet suitable for all kidney stone patients. Different types of stones develop through different mechanisms and require individualized nutritional strategies.

Therefore, patients are encouraged to bring their 24-hour urine test results, stone composition analysis reports, and medical records when consulting a clinical nutrition specialist. Personalized dietary guidance can significantly reduce the risk of recurrence and help protect long-term kidney health.