Life Extension Magazine®

Issue: Mar 2000

K in the Tea

Vitamin K in Tea, I3C vs. Tamoxifen.

Scientifically reviewed by: Dr. Gary Gonzalez, MD, on January 2021.


Q: Recently, I came across a health columnists who said that green tea has a lot of vitamin K, and that people like me who take Coumadin shouldn't drink it. Is this true?

A: The information you read appears to be outdated. According to researchers at Tufts University, brewed tea and coffee do not have sufficient vitamin K to worry over. However, green tea capsules may. If you are taking a blood thinner, inform your doctor if you would like to take green tea capsules, as your dose may need to be adjusted to account for the vitamin K.

Q: Is there any affiliation between Life Extension and Durk Pearson & Sandy Shaw, authors of the book Life Extension? How can I learn more about Durk and Sandy's research?

A: In the past, Durk and Sandy have contributed to some of our newsletters and to Life Extension magazine. Life Extension is also licensed to manufacture several of their unique formulations. You may find some of their written contributions by clicking here.

Q: Your I3C article in the October issue of Life Extension magazine doesn't appear to discuss the questions of the use of I3C vs. tamoxifen when used as adjuvant therapy for patients with known breast cancer. Can you provide scientific backup/references for your conclusions as written in your article, of interest to medical oncologists who are currently prescribing tamoxifen for their breast cancer patients as adjuvant therapy after mastectomy?

A: We do not intend to impart the distinction that I3C is a tamoxifen replacement for patients with existing cancers. The information presented was solely to inform the reader of the possible benefits of I3C as a preventative and the possible role it may play as an adjuvant item. In fact, we recommend that most breast cancer patients consider two years of tamoxifen drug therapy if their physician prescribes it.

Here are a few supportive references regarding I3C:


  • Cancer Res 1999 Mar15;59(6):1244-51
  • Curr Med Chem 1998 Dec;5(6):469-91
  • J Cell Biochem Suppl 1997;28-29:111-6
  • J Biol Chem 1998 Feb 13;273(7):3838-47
  • Anticancer Res 1997 Nov-Dec;17(6D):4333-7
  • Cancer Lett 1997 Sep 16;118(1):87-94
  • J Natl Cancer Inst 1997 May 21;89(10):718-23