As with many alternative remedies, the exact composition of essiac is unclear, but it reportedly contains burdock (Arctium lappa), Indian rhubarb, sheep sorrel (Rumex acetosella), and slippery elm bark (Ulmus rubra). Some formulations may also contain watercress, blessed thistle, red clover, and kelp. From the 1920s through the 1970s, essiac was promoted as a cancer treatment by Rene Caisse, a Canadian nurse, who claimed that it had been given to her by a patient and that the recipe derived from an Ontario Ojibwa medicine man. The name "Essiac" is Caisse's surname spelled backwards. Today, Essiac is often sold with apparatus (such as bottles as infusers) for making the tea, and is sometimes promoted with untrue claims that scientific studies have shown it to be effective.
In 1977, Caisse sold the essiac formula and trademark rights to Respirin Corporation (a Canadian company and predecessor in title to Essiac Products Inc.), which attempted to commercialize the product. However, the company was unable to show any efficacy of essiac against cancer. Repeated laboratory tests showed that essiac failed to slow tumor growth and, in large doses, killed test animals. In a number of studies, essiac actually increased the rate of cancer growth. As a result both the U.S. and Canadian governments refused to approve essiac as a medical treatment. Essiac was instead marketed by Essiac Products Inc. and others as a dietary supplement, subject to much looser regulation and not required to show any proof of effectiveness.
Essiac's purported effect on cancer has been reviewed by several major medical and scientific bodies, including the U.S. Food and Drug Administration, the National Cancer Institute, and the American Cancer Society. The American Cancer Society state that "Reviews of medical records of people who have been treated with Essiac do not support claims that this product helps people with cancer live longer or that it relieves their symptoms." The NCI states "Essiac and Flor Essence have not reported clear evidence of an anticancer effect" and The U.S. FDA described essiac as a "Fake Cancer 'Cure' Consumers Should Avoid". Researchers at Memorial Sloan-Kettering Cancer Center have written that Essiac continues to be a popular cancer therapy despite unsubstantiated claims of its effectiveness.
Cancer Research UK also notes that there is "no scientific evidence that Essiac can help to treat cancer or control its symptoms" and cautions that "Essiac may interact with some types of cancer treatment so it is very important to tell your doctor if you are thinking of taking Essiac."
- Barrett, Stephen (July 27, 2010). "Questionable Cancer Therapies: Essiac". Quackwatch. Retrieved July 5, 2011.
- "Essiac tea". American Cancer Society - Complementary and Alternative Medicine. American Cancer Society. Retrieved 24 May 2011.
- "Questions and Answers About Essiac and Flor Essence". National Cancer Institute. February 19, 2013. Retrieved May 6, 2013.
- "Patient Information: Essiac/Flor Essence". National Cancer Institute. July 21, 2010. Retrieved July 5, 2011.
- "Essiac". Cancer Research UK. Retrieved Agugust 2013.
- "187 Fake Cancer "Cures" Consumers Should Avoid". Guidance, Compliance & Regulatory Information. USFDA. Retrieved 24 May 2011.
- "Essiac/Flor Essence". Retrieved August 7, 2013.
- "Essiac". Memorial Sloan-Kettering Cancer Center. March 10, 2011. Retrieved December 15, 2012.