Kidney Stones: Types & Prevention

Kidney stones are hard deposits that form in the kidneys when high levels of certain minerals bind together and create crystals in the urine.

Types of Kidney Stones

There are four main types:

• Calcium oxalate or calcium phosphate — the most common (70–80%)
• Uric acid stones
• Struvite stones (about 10%)
• Cystine stones (less than 1%)

Prevalence is estimated at 10–20% in Asia and 15–18% in Western countries. While kidney stones were previously more common in men, the gender gap has narrowed.

Signs and Symptoms

• Severe pain in the side, back, lower abdomen or groin
• Burning or painful urination
• Frequent urination of small amounts
• Cloudy, foul-smelling, pink, red or brown urine
• Nausea, vomiting, fever or chills in more severe cases

Small stones may pass with little or no pain. Larger stones can block urine flow and cause intense pain that may require medication or, in severe cases, surgery.

Dietary Management

General daily targets include:

• Sodium: less than 2300 mg
• Calcium: 800–1200 mg
• Oxalate: 40–50 mg
• Protein: 0.8–1.4 g per kg body weight
• Fluid: more than 2.5 litres
• Vitamin C: keep supplements under 1000 mg

Reduce Sodium

Limit salt to no more than 1 teaspoon per day. Use herbs and spices instead of salt, and reduce high-sodium foods such as canned items, processed meats, sauces and fast food.

Manage Oxalate

Limit high-oxalate foods such as spinach, beetroot, rhubarb, certain nuts, chocolate and wheat bran. Pair oxalate-rich foods with a calcium source (for example, chocolate with milk or almonds with yoghurt) so that calcium can bind oxalate in the gut and reduce absorption.

Get Adequate Calcium

Cutting calcium is a common misconception. Adequate calcium intake actually helps reduce calcium-oxalate stone risk by binding oxalate in the intestine. Choose lower-salt dairy or non-dairy sources such as chia seeds, broccoli, chickpeas and kale.

Moderate Protein

High animal protein (especially organ meats and certain fish) can increase uric acid and make urine more acidic. Favour more plant-based proteins such as beans, lentils and peas while keeping animal protein moderate.

Drink Enough Fluid

Aim for at least 2.5 litres of fluid daily, preferably plain water. Adding lemon juice is fine. Avoid sugar-sweetened drinks.

Avoid Excess Vitamin C Supplements

High-dose vitamin C can increase oxalate production. Prefer food sources of vitamin C over large supplements.

Diet Tips by Stone Type

• Calcium stones: Lower sodium and oxalate, adequate calcium, moderate protein, high fluid, avoid high-dose vitamin C.
• Uric acid stones: Limit high-purine foods (red meat, organ meat, certain fish and shellfish), sugar-sweetened drinks and alcohol; maintain high fluid intake.
• Struvite and cystine stones: Usually require medical or surgical treatment rather than diet alone.