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Diet and Nutrition

Kidney Stones and Foods High in Oxalates

09/17/1999

Question:

What foods are high in oxalates? I am looking for a possible link to kidney stone formation, as mine was analyzed to be calcium oxalate. Are there any links to kidney stone formation between lactose intolerance or diabetes?

Answer:

Oxalate is a type of acid found naturally in foods primarily of plant origin (such as green leafy vegetables, beans, celery, beets, chocolate, coffee, tea, and peanuts*). It is not essential to life. Once we eat oxalate, it is sent through our body and is excreted in the urine unchanged. When too much oxalate is excreted into the urine, "kidney stones" are formed (in fact, 75% of all kidney stones in the U.S. are oxalate stones).

Researchers believe that oxalate stones may be caused by:

Certain diseases (especially intestinal disease, chronic kidney infections, or bypass surgery),

Metabolic disturbances, Hormone imbalances (overactive parathyroid glands)

Inadequate fluid intake

Lesions that block the flow of urine, and

Large doses of vitamin C (>4 grams per day) taken regularly

In addition, recent studies have shown that calcium is no longer considered a cause of stones. Researchers are finding that people who eat the most calcium develop 1/3rd fewer stones than others. Calcium may aid actually in flushing the oxalates from the body. So, as a lactose intolerant person, you may want to make sure you are getting enough calcium.

The primary treatment for oxalate stones is to use medication. Diet is also used as a preventative measure to lower your risk of developing future stones. In general, these guidelines are recommended:

1. avoid large amounts of foods high in oxalates*

2. eat a low fat diet (people with oxalate kidney stones absorb and digest fat poorly)

3. drink at least 3 quarts of fluid daily. This helps keep the concentration of oxalate in the urine down and reduces the chance of stones forming.

4. Avoid vitamin C supplements over the RDA (recommended dietary allowance). Vitamin C is converted to oxalate by the body in some people

5. Cut down on protein (especially meat)

6. Increase your intake of potassium-rich fruits and vegetables (potassium protects against kidney stones)

7. Eat plenty of complex carbohydrates

*More foods that are high in oxalate include: beans (baked, wax, dried, green) tofu, beets, greens (dandelion, collards, mustard, swiss chard, escarole, kale, spinach), chive, eggplant, leeks, okra, parsley, peppers, sweet potatoes, summer squash, watercress, berries (blue, black, dew, goose, raspberries, strawberries), concord grapes, red currants, fruit cocktail, lemon or lime peel, orange peel, rhubarb, tangerine, grits, white corn, wheat germ, pecans, cocoa, pepper (over 1 tsp. per day), vegetable soup, tomato soup, and beer.

If this "foods to avoid" list seems overwhelming, please contact a Registered Dietitian (RD) in your area. The RD can individualize a diet specific to your needs and preferences. Best of Health to you!

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Response by:

Jane   Korsberg, MS, RD, LD Jane Korsberg, MS, RD, LD
Senior Instructor of Nutrition
School of Medicine
Case Western Reserve University