Frequently Asked Questions

Can green tea capsules increase chance of bleeding and bruising for any type of surgery?

You have asked a very good question.

The process leading to blood clotting is complex with multiple steps involved. One concern comes from the high vitamin K content of green tea leaves, which in excess amounts could potentially interfere with the clotting mechanism, causing bleeding or bruising. This is not usually a concern when people drink a moderate amount of green tea because vitamin K is a fat soluble vitamin and is not extracted into the tea in an appreciable amount by the brewing process with water.

However, as with everything, the dose is the poison. There is one case report of a gentleman consuming 1/2 to 1 gallon of green tea each day with lab tests indicating that it took his blood a longer time to clot than desired (Ann Pharmacother. 1999 Apr;33(4):426-8. Probable antagonism of warfarin by green tea. Taylor JR, Wilt VM). If one were actually ingesting the green tea leaves, in addition to the tea, then the potential for prolonged clotting time leading to bruising or bleeding would be increased even more.

In addition, an animal study has shown that the components of green tea called catechins (the main catechin is called (-)-epigallocatechin gallate or EGCG) also can prolong bleeding time by interfering with the function of platelets. (Thromb Res. 1999 Nov 1;96(3):229-37. Antithrombotic activities of green tea catechins and (-)-epigallocatechin gallate. Kang WS, Lim IH, Yuk DY, Chung KH, Park JB, Yoo HS, Yun YP.)

However, one human study using green tea extract capsules of 3 grams per day (equivalent to 10 cups of tea per day) for 4 weeks did not show any changes in coagulation indicators compared to those receiving the placebo. (Eur J Nutr. 1999 Jun;38(3):149-57. Green tea extract decreases plasma malondialdehyde concentration but does not affect other indicators of oxidative stress, nitric oxide production, or hemostatic factors during a high-linoleic acid diet in healthy females. Freese R, Basu S, Hietanen E, Nair J, Nakachi K, Bartsch H, Mutanen M.)

The American College of Anesthesiologists does advise stopping all herbs and other dietary supplements 2 weeks before surgery when possible, which is the prudent thing to do. They have a brochure that may be downloaded from their website discussing several common herbs and potential complications during anesthesia and surgery. It is very important to remember that combinations of various dietary supplements may produce unexpected and deleterious effects, also.

Please discuss this information with your physicians and disclose to them all of the various dietary supplements you are currently taking. Please also read the information I have in an another Q&A about herbs that may potentially interfere with clotting.

FAQ posted 8/03

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Back to Main QandA Page Tea Does decaffeinated green tea still have the health promoting phytochemical called Epigallo-catechin-gallate (EGCG)? posted 1/01 What other teas are healthful to drink in addition to green tea? Is white tea better than green tea for cancer patients? posted 2/03 Can green tea capsules increase chance of bleeding and bruising for any type of surgery? posted 8/03 Is it safe to drink green tea if I have a port for administration of my chemotherapy? posted 1/04 Can drinking tea reduce the absorption of iron, contributing to low red cell counts and iron-deficiency anemia? posted 8/04 Do flavored green teas have the same anti-cancer activity as plain green tea? posted 10/04 Should I be avoiding all caffeine to help fight my breast cancer? posted 11/04  Does adding milk to tea reduce its anti-cancer benefit? posted 11/04 What you think about the Jason Winters tea? posted 5/05 Should I stop drinking green tea during chemotherapy to avoid consuming too many antioxidants? posted 7/05

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These questions and answers are intended to be of a general informative nature. Please consult with the Registered Dietitian in your cancer center or your health care provider for nutritional advice that can be individualized to your specific medical condition.