Essiac Tea: Is It a Real or Fake Cancer Cure?

Hands holding a cup of tea leaves.

Rumors of a cancer-curing tea originating in the forests of Ontario, Canada, began circulating in the 1920s.

The tea’s ingredients were kept secret. Canadian nurse Rene M. Caisse held the only recipe, and she fervently protected it until just before her death.

Caisse said the herbal recipe came from an English miner’s wife who claimed a Native American Indian healer from Ontario had cured her of breast cancer with the tea 20 years earlier. Caisse named the tea Essiac (the reverse spelling of her last name) and reportedly gave it to cancer patients for free.

Not only are its origins and healing properties steeped in mystery, Essiac tea is also linked to federal restrictions on its use, a report of toxicity and a death.

Today, thousands of people with cancer, including some with mesothelioma, use Essiac tea as an alternative medicine hoping it will help them reach remission. A survey from 2000 found 15 percent of Canadian women with breast cancer use Essiac. A separate U.S. survey of 5,051 Essiac users found 22 percent had breast cancer.

The human research conducted on Essiac hasn’t held much clout in scientific communities. Though some laboratory studies have published results, peer-reviewed scientific journals have not published any clinical trial involving humans. Results of human studies completed in the 1970s were kept hidden.

Homemaker's Magazine article with Rene Caisse

Homemaker’s Magazine article on Rene Caisse from 1977.

Caisse alleges she observed an 80 percent survival rate among all cancers with Essiac treatment, a figure that’s never been backed by records or scientific study.

Despite a furtive history, the herbs in Essiac may offer some health benefits.

Herbs Pack Antioxidant Punch

The original herbal ingredients of Essiac eventually became known: Burdock root, rhubarb root, sheep sorrel and slippery elm bark.

Research on these herbs show they have compounds that protect DNA from damage and can influence the immune system.

Roots of burdock and rhubarb show anti-cancer properties in test tube and rat studies; however, they also contain carcinogenic properties.

A Chinese study showed rhubarb extract significantly reduced pulmonary toxicity among lung cancer patients receiving radiation therapy.

Slippery elm bark contains mucilage, a gelatinous substance that may relieve coughs and throat irritation. It may offer relief to pleural mesothelioma patients coping with pulmonary symptoms.

A 2007 Canadian study conducted in a lab with no human test subjects revealed Essiac contains more antioxidant properties than red wine or green tea. No antibacterial effects were observed, but Essiac did stimulate several immune system cells and enzymes.

The National Institute for Occupational Safety and Health examined the antioxidant power of Essiac in a 2006 study and found it effectively protected DNA from free radical damage. This DNA-protective effect won’t repair damage that already led to cancer, but it could have a preventative effect with long-term use.

Reported side effects of Essiac include nausea, vomiting, frequent urination, increased bowel movements, swollen glands, headaches, flu-like symptoms and skin blemishes.

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Secret Recipe Brews Controversy

The origins of the formula are debated because several of the herbs are not indigenous to North America and reportedly hadn’t yet made it to the Americas through trade routes when Caisse first promoted the tea.

Originally, Caisse brewed three of the herbs into a tea and injected the other herb intramuscularly. No one but Caisse knew which herbs were brewed and which one was injected.

Rene Caisse discusses Essiac tea.

The fact that the formula and preparation was kept secret became a road block to scientific research and a source of controversy in later investigations.

Caisse provided Essiac to cancer patients at the Bracebridge Cancer Clinic in Ontario starting in 1935. Evidence of a reported death and one report of toxicity caused the Cancer Commission of Canada to investigate the clinic in 1938. Although the Canadian government shut down the clinic in 1941, Cassie continued to provide Essiac to cancer patients from her home.

During the ’60s and ’70s, Caisse worked with American physician Dr. Charles Armao Brusch to modify the Essiac recipe and promote its use. Brusch also served as President John F. Kennedy’s personal doctor.

Brusch and Caisse performed clinical and laboratory studies, but they never published the results. They expanded the recipe with four additional herbs: Blessed thistle, kelp, red clover and watercress. The pair named the new blend Flor-Essence. This new formula contained the formerly injected herb and with its inclusion, Caisse stopped providing injections.

In 1977, a year before her death, Caisse sold the original, four-ingredient Essiac recipe to a Canadian corporation. That company filed a preclinical new drug submission with the Canadian Department of National Health and Welfare (CDNHW). The company received approval and began clinical studies of Essiac in cancer patients. But in 1982, the CDNHW learned the study wasn’t being conducted as planned and stopped the research.

The secret Essiac recipe was sold again, this time to Essiac Products Inc., which currently makes and sells a variety of Essiac supplements. Flor-Essence is manufactured in British Columbia, and Brusch was reportedly involved in its production before his death. Today, several companies manufacture more than 40 different Essiac formulas and sell them worldwide.

Some promoters of Essiac say it should not be taken alongside traditional cancer treatments like chemotherapy. If cancer patients take Essiac as a first-line treatment or instead of traditional cancer treatment, they run the risk of their cancer progressing to the point that traditional treatment will no longer be effective.

Dr. Andrew Weil, a widely-known supporter of natural medicine, warns, “[S]ome Essiac promoters irresponsibly advise against chemotherapy and other conventional treatments when using the tea to help it work effectively. This is a reckless and dangerous recommendation. There is no clinical evidence that either Essiac or Flor-Essence has any anti-cancer activity. My advice? Avoid it.”

Research on Essiac

Scientific research on Essiac has yielded conflicting results.

All human clinical trials were either stopped by government authorities or kept hidden from the public.

An unpublished 1977 report of a Phase II clinical study of Essiac in cancer patients found the tea did not affect survival or shrink tumors.

The tea contains antioxidants, which help to counteract the effects of aging and exposure to toxins like asbestos, and it slowed growth of certain cancer cells in test tubes. However, one study showed it stimulates breast cancer growth and another found no effect on prostate cancer cells.

Overall, research has confirmed Essiac’s antioxidant power and presented no evidence that it can cure cancer.

In 2009, the U.S. Food and Drug Administration cited a brand of Essiac tea on a list of fake cancer cures that consumers should avoid.

Consumption of Essiac is unlikely to cause serious side effects among people with mesothelioma when used as directed. The antioxidant potential in Essiac may be the tea’s most noteworthy health benefit.


Joining the team in February 2008 as a writer and editor, Michelle Whitmer has translated medical jargon into patient-friendly information at for more than eight years. Michelle is a registered yoga teacher, a member of the Academy of Integrative Health & Medicine, and was quoted by The New York Times on the risks of asbestos exposure.

18 Cited Article Sources

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