For patients prone to recurrent kidney stones, dietary prevention can be effective if no other chronic conditions are contributing to the presence of kidney stones (nephrolithiasis). Certain foods and drugs may contribute towards preventing kidney stones but it is important to first consult with your doctor to confirm/exclude other contributing factors.
Calcium and Kidney Stones
Contrary to popular belief, a normal calcium intake may play a role in preventing kidney stones. While calcium oxalate stones are by far the most common type of kidney stone, it is the high oxalate output that is one of the predisposing factors for kidney stones. Calcium binds with oxalate in the gastrointestinal tract thereby lowering the absorption and excretion.
A normal calcium diet does not mean that the calcium level in the blood will be high. The body regulates the calcium levels in the blood but in certain conditions, this may be disrupted thereby leading to hypercalcemia (high calcium levels in the blood) even if the dietary calcium intake is low. Any cause of hypercalcemia or hypercalciuria (high calcium levels in the urine) may increase the risk of developing kidney stones. This should not be confused with dietary calcium and a diet low in calcium may result in the formation of oxalate stones.
Unused calcium is passed out of the body through the urine. It can combine with a number of other substances and waste products, like oxalate, to form kidney stones. Even in normal amounts, calcium in the urine may form kidney stones by binding to other substances.
Kidney Stones Diet
Fluid intake is important for the prevention of kidney stones. Water is the best option and any person who is at risk of developing kidney stones should consume 2 to 4 litres of water a day. Avoid drinks that may contribute to dehydration like coffee, alcohol and caffeinated soft drinks. The fluid intake should be spread out during the course of the day.
List of Foods to Avoid
Most kidney stones are calcium oxalate stones (75% to 80%). Struvite stones (10% to 15%) are a result of repeated infections which affect the pH of the urine – dietary changes are insignificant in preventing the formation of these stones. Uric acid stones constitute some 5% of kidney stone cases and dietary changes can be beneficial for preventing the formation of these stones.
Calcium Oxalate Stones
Reducing the intake of foods rich in oxalate is essential in preventing these types of kidney stones. Spinach and rhubarb are two vegetables that are very high in oxalate compared to other foods.
Other foods include :
Vegetables, Fruits and Grains
- Green pepper
- Red raspberries
- Sweet potatoes
- Swiss chard
- Wheat bran
- Wheat germ
High meat intake should be avoided. This includes red and white meat and fish. Offals (example : liver) should be avoided altogether.
Processed and Prepared Foods
- Bran muffins, cereals
- Cakes with fruit
- Peanut butter
- Soybean foods
- Cola drinks
- Certain energy drinks
- Vitamin D supplements should be avoided as it increases calcium absorption.
- High intake of vitamin C supplements (mega doses) increases oxalate excretion through the kidneys.
Uric Acid Stones
Many of the dietary changes for the prevention of calcium oxalate stones may also be helpful for uric acid stones.
- Alcohol should be avoided.
- Caffeinated drinks should be limited.
- Legumes like lentils should be limited or avoided altogether.
- Meat intake, especially offals, should be reduced.
- Dairy intake should be moderate.
Any dietary supplement that can make urine more alkaline like sodium bicarbonate may be helpful for uric acid stones as they are more soluble at a pH levels higher than 6.