Oxalic Acid in Fruits and Vegetables: Something to Worry About?

Sara Lovelady Mar 26, 2014

Juice Plus+ recently received this customer inquiry:

“Can we please see something about oxalate risks & veg. contents? I've found sites saying kale is low & others fairly high. what to believe? Can high oxalate cause joint knee pain? Oddly, since ramping up my raw kale intake ive experienced this. is there a connection? ”

Ask and you shall receive!

Oxalic acid is formed naturally by the body and is also present in many vegetables. Because it binds with calcium, when consumed in large quantities, oxalic acid can interfere with your ability to absorb calcium and can also form a compound called calcium oxalate. Kidney stones are the health problem most commonly associated with calcium oxalate, but in rare cases, similar small crystals of calcium oxalate can form in the synovial fluid of joints and cause pain.[1]

It’s important to note that most people don’t need to restrict their oxalic acid consumption. But for those prone to kidney stones, the University of Pittsburgh Medical Center recommends a low-oxalate diet of no more than 40-50 mg per day.[2]

Different websites do provide conflicting information about the oxalate content of various vegetables — kale in particular. Apparently, this is because using different analytical techniques to measure oxalate can produce widely divergent results.

But according to a report published by The General Clinical Research Center at the University of California San Diego Medical Center— the most authoritative source I could find — raw kale contains a moderate amount of oxalic acid, defined as 2-10 mg per serving.[3] Foods high in oxalate include: spinach, rhubarb, cocoa, chocolate, tea, beer, peanut butter, green beans, beets, Swiss chard, collards, eggplant, sweet potatoes, blueberries, Concord grapes, raspberries, wheat products (especially bran), and certain nuts.

If you’re concerned about oxalic acid, here are three ways to limit your intake:

  • Cut down on certain foods. If you’re thinking of avoiding all the foods in the list above, don’t! (That is, unless you have kidney stones.) The sad truth is that most Americans don’t eat nearly enough fruits and vegetables. Increasing your produce consumption is one of the best steps you can take to improve your overall health. Cut down on non-essential high-oxalate foods like cocoa, chocolate, beer, peanut butter, and wheat bran instead.
  • Cook (at least some) of your vegetables. Cooking vegetables that are high in oxalic acid releases any calcium bound to the substance, making the calcium available for your body to use and preventing the formation of calcium oxalate.[4] It’s fine to eat a kale salad every now and then, just don’t eat raw kale for breakfast, lunch, and dinner.
  • Eat a varied diet. It’s always a good idea to vary the types of vegetables you eat and not to binge on any one. Not only will this strategy avoid excess oxalic acid, it will maximize your consumption of all the health-giving nutrients that different vegetables contain.

“What about Juice Plus+?” you’re probably wondering. Juice Plus+ has been independently tested for oxalic acid content, and the news is good. Taking two capsules each of the Fruit, Vegetable and Berry blends provides less than 20 mg of oxalic acid, a fairly low amount when you consider it adds the nutrition of 25 different fruits, vegetables, and grains to your diet.

Have any additional inquiries about the health benefits of fruits and vegetables? Let us know your burning questions in the comment section below.


[1] Lorenz EC, et al. Update on oxalate crystal disease. Curr Rheumatol Rep. 2013 Jul;15(7):340.

[2] Low oxalate diet may help prevent kidney stones. UPMC. 2014.

[3] Brezinski E, et al. Oxalate content of selected foods. The General Clinical Research Center, University of California, San Diego Medical Center. 1996:1-52, in: Fugh-Berman A. The 5-Minute Herb & Dietary Supplement Consult. Philadelphia: Lippincott Williams & Williams. Philadelphia, 1996: 454-456.

[4] Beck L. Is spinach more nutritious raw or cooked? Globe and Mail. 2010 Dec 8 (updated 2012 Aug 23).

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