Written by Katja Boehm and the CAM-Cancer Consortium.
Updated February 8, 2017


Does it work?


Three reviews exist in the peer-reviewed literature1,2,12, which did not identify a single published clinical trial. The first review, by Kaegi et al.1 discusses the history and safety of Essiac along with laboratory and clinical evidence. The second review by Boon et al.2 reviews the efficacy and safety of various botanical medicines (including Essiac). The third is a systematic review carried out in the USA by researchers at Natural Standard (an international multidisciplinary collaboration including contributors from more than 100 academic institutions) showed a lack of high-quality clinical trials to substantiate any of Essiac's traditional uses12. The results are inconclusive despite indications from preclinical, animal and laboratory data suggesting possible positive effects caused by Essiac application.

Controlled trials

No controlled studies are available.

Epidemiological studies

In a retrospective cohort study of Essiac to ascertain its effects in women with breast cancer in Canada, 510 women with a positive breast cancer pathology report who were diagnosed between 2001 and 2003 responded to a mail survey13. The survey packet included a) the Functional Assessment of Cancer Therapy Breast Cancer Version (FACT-B), b) the Profile of Mood States (POMS), c) the Yale Social Support Index (YALE), d) Patterns of use of Essiac and e) prevalence of general use of complementary and alternative medicine. Overall, 8.1% of the surveyed women were using Essiac. Results showed that there were differences on one of the subscales regarding health-related quality of life (physical well-being) as assessed by the FACT-B scale (p<0.02) between Essiac users and non-users for which Essiac users seemed to score better. However, on all other subscales, women who reported Essiac use consistently had higher scores compared to non-users, meaning that scores for health-related quality of life and mood were generally worse in Essiac users. Furthermore, Essiac seemed to have a negative effect on users as those reported scores indicating a higher burden due to their disease. Dose, frequency of use and brand of Essiac product did not affect disease-specific QoL or various mood states on the POMS. However, the authors of the survey put forward the likely explanation that Essiac use is a marker of physical distress. Only two adverse events were reported in this survey, involving mild gastrointestinal upset and an unpleasant taste.

Case series/reports

A Canadian study collected case reports submitted voluntarily by physicians. This case series included 86 patients with advanced cancers who had been treated with Essiac7. Forty-seven patients received “no benefits”, eight of the reports were impossible to evaluate, 17 patients died, one patient experienced ‘subjective improvement’, five required fewer analgesics, four had an ‘objective response’, and four were in ‘stable condition’. All of the patients also received conventional treatment, which could have explained their improvement.

Pre-clinical studies

Essiac was tested in a mouse sarcoma model in the US by the Memorial Sloan Kettering Laboratories, New York, in 1959 and again from 1973 to 197614,15. Some unpublished preliminary reports suggested some evidence of biological activity. The results of six immunotherapy tests and two chemotherapy tests of Essiac samples as tested on the mouse sarcoma model, showed no activity.

An in-vitro study comparing Essiac® and Flor-Essence® in human breast cancer cells found that both of the teas demonstrated antiproliferative and differentiation inducing properties, but this effect was only observed at high concentrations (1/10 and 1/100)3.
Most of Essiac’s identifiable components have shown anti-cancer properties individually16-24.

In a Canadian animal lab study Essiac was administered orally to rats25. The administration demonstrated a modest gastric protective effect. In 2006 a U.S. study wanted to assess the effect of Flor-Essence® and Essiac® on cell proliferation. Herbal tonics were tested in various types of cancer cells isolated from human breast tumors26. It was found that Flor-Essence® and Essiac® herbal tonics can stimulate the growth of human breast cancer cells in vitro through estrogen receptors mediated as well as estrogen receptors independent mechanisms of action.

A Canadian-Australian research team carried out another in vitro analysis of Essiac® by measuring its activity27. The in vitro analysis showed significant antioxidant and immuno-modulatory properties as well as neoplastic, cell specific cytotoxicity,.
Another Canadian research team evaluated the anti-proliferative effects of Essiac TM on in vitro and in vivo models of prostate cancer compared to Paclitaxel. The investigations showed no marked anti-proliferative effect28.


Katja Boehm, CAM-Cancer Consortium. Essiac [online document]. http://cam-cancer.org/The-Summaries/Herbal-products/Essiac. February 8, 2017.

Document history

Assessed as up to date in February 2017 by Barbara Wider.
Assessed as up to date in April 2016 by Barbara Wider.
Assessed as up to date in January 2015 by Barbara Wider.
Assessed as up to date in February 2013 by Katja Boehm.
Fully revised and updated in December 2011 by Katja Boehm.
Fully revised and updated in August 2009 by Katja Boehm.
Summary first published in May 2005, authored by Katja Boehm and Edzard Ernst.


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