Calcium Oxalate Stone (Kidney Stone) Prevention
Most Kidney Stone are Oxalate stones.
So what can you do to minimize getting these?
Read on to find out.
Keep taking calcium
Calcium restriction was once the advice given to stone formers, and you may hear this even today. This is no longer recommended because:
- Cutting down on calcium increases the risk of stone formation.
Most calcium in the diet remains in the gut where it binds to oxalate from food and the liver. The bound oxalate cannot be absorbed and is excreted in the faeces. This means it never enters the bloodstream or the kidneys and never causes stones.
- Calcium is an essential nutrient
A low calcium diet can lead to osteoporosis, a crippling bone disease seen in many elderly men and women. Osteoporosis is preventable in many people by taking a high calcium diet.
Oxalate is common in foods, and it is not difficult to consume a large amount of oxalate within an otherwise healthy diet. This can increase the risk of developing stones.
Please keep in mind that you still have to eat. You will never have a perfect diet and any of the above in moderation are fine for stone formers. It is excessive intake which is the problem in a few people.
Below is a list of common foods high in oxalate:
Tops, Roots, Greens
Chard, Swiss Chive
Soybean curd – (Tofu)
Grits, white corn
Juices containing berries
Mixed beverage mixes (Milo, Ovaltine)
A high sodium (salt) diet is one of the strongest contributors to stone disease in western society. Sodium exchanges for calcium in the kidney. A diet high in salt puts more calcium into the urine. The obvious way to reduce salt intake is not to add it to your cooking and remove the salt shaker from the table. Restriction of salty foods like preprocessed or take-away foods is also very helpful.
The western diet is high in protein. This creates a large amount of acid in the body which the kidneys must excrete. Long term this results in extra calcium in the urine and the depletion of bone calcium, which causes osteoporosis. Food high in protein include all meats, nuts, soy and dairy products. You can try having vegetarian pasta or pizzas with low fat cheese instead of the typical meat and three vegetables meal.
There is no doubt that water intake is important to stone formers. Stones can develop within a few minutes in the laboratory if the components are found in a high enough concentration. In the body stones may progressively grow during favorable times i.e. after a high oxalate / protein load on a hot day. If you can consistently drink enough water to keep your urine a pale to transparent colour you will significantly reduce the risk of stones.
Vitamin supplementation is becoming more popular. Vitamin C has been recommended in very high doses by some. Vitamin C is broken down in the liver into oxalate. 40% of body oxalate comes from this source normally. Studies in normal people have shown conflicting evidence on the effect of vitamin C on urinary oxalate. Most vitamin C is in the form of sodium ascorbate, giving a high dose of salt also. Whilst vitamin C appears safe it may contribute to stones in a few people, with the high doses of sodium another negative.
Citrate is an important naturally occurring inhibitor of calcium stone formation in urine. Citrate attaches to calcium in the urine, preventing the formation of mineral crystals that can develop into kidney stones.
Citrate also prevents the urine from becoming too acidic. This helps prevent uric acid or cystine kidney stones from forming.
Foods that are high in citrate include:
orange juice, bananas, boiled chard, mushrooms, raw, fennel (bulb), romaine lettuce, raw celery, boiled mustard greens, raw cauliflower, raw broccoli, all varieties of summer and winter squash, ripe tomatoes, cooked turnip greens, raw carrots, boiled collard greens, raw cabbage, eggplant, cantaloupe, boiled beets, papaya, snap and string green beans, yam, fresh kale, and Brussels sprouts.
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About Dr. Tan
Dr. Tan graduated from the National University of Singapore in 2001. His residency was in the two largest public hospitals in Singapore; Tan Tock Seng Hospital and Singapore General Hospital.