Coumadin is a blood-thinning prescription drug administered by doctors to people who have thick blood. Anyone prescribed with this drug will be informed by their doctor to avoid consuming foods that are high in vitamin K since this vitamin is responsible for thickening the blood naturally as a way to heal wounds. Too much vitamin K in the diet can counteract the blood-thinning effects of Coumadin.
Green Tea and Coumadin
The issue of taking green tea while using Coumadin has been raised because green tea leaves contain high levels of vitamin K. However, this should not scare Coumadin users away from drinking green tea and receiving its many and well documented benefits for health. Even though the actually leaves contain lots of vitamin K, only minimal amount of this vitamin actually make it into the brew. Vitamin K is a fat soluble nutrient, not water soluble. The Journal of the American Dietetic Association reported in 1995 that 3.5 fluid ounces of green tea contains just 0.03 mcg of vitamin K. Such a small amount is practically negligible.
Coumadin and Green Tea Extract
Taking green tea extract is a different story to drinking the tea since we are now dealing with solids. Even so, we are talking about an extract, and not eating the whole leaf. It is primarily the polyphenol antioxidants that are extracted, but other nutrients will be present also. The problem is that it is hard to find out solid information about how much vitamin K is actually in green tea extracts, and the amount will vary between the extraction methods of one company compared with another. So, it is probably advisable to avoid mixing Coumadin and green tea extract unless the product you are using clearly states the amount of vitamin K that it contains. Always better to be safe!
One great option for green tea extract is a supplement called EGCG Ultra by Dr. Ronald Hoffman. It is one of the highest quality green tea extract supplements available and contains no vitamin K and no caffeine. Additionally, this product does not contain any starch, yeast, corn, egg, wheat, soy, dairy, salt, sugar, artificial coloring, flavorings or preservatives. Learn more about this product here.