Are Astringent Tree Barks Harmful?
Answered by: Susan Eagles
Question from: Maureen
Posted on: September 15, 2006

My husband had a colonoscopy yesterday. There were blackened areas which the doctor claims are from the tree bark derivatives in his colon cleanser and other herbal supplements. Since I also use these supplements, I am wondering how much truth there is to this and since the doctor didn’t seem concerned, is there really any danger in the tree bark stains?

I haven’t heard of a colonoscopy showing dark stains due to herb barks. Since the doctor did not seem concerned, he may be referring to a stain caused by tannins, like a tea stain. Tannins are substances in all tree barks, in nearly all digestive herbs, in tea and coffee and certainly in all herbal colon cleansers. Tannins act to astringe the area they come into contact with, reducing secretions including bleeding, and reducing inflammation. These stains are not harmful, but it is not desirable to be astringed on a constant basis. Herbs should be used short term to correct a condition. Then the condition should be reassessed for current needs.

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