Essiac Tea for Mesothelioma

Fact Checked

Essiac is a blend of herbs, usually consumed as tea, promoted as an alternative treatment for cancer. Scientific research does not support claims that Essiac cures cancer. But Essiac does contain antioxidants that protect against DNA damage.

Essaic tea leaves

Rumors of a cancer-curing tea originating in the forests of Ontario, Canada, surfaced in the 1920s. The tea’s ingredients remained secret for decades. Canadian nurse Rene M. Caisse held the only recipe, and she protected it until just before her death.

Caisse said the herbal recipe came from an English miner’s wife. The wife claimed a Native American 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 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 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. In 2006, a separate U.S. survey of 5,051 Essiac users found 22 percent had breast cancer.

The research conducted on Essiac in humans hasn’t held much clout in scientific communities. Results of human studies completed in the 1970s were kept hidden. Some studies of the effect of Essiac on cancer cells in test tubes or in animals have been published, but no peer-reviewed scientific journal has published any clinical trial of Essiac in humans.

Caisse alleges she observed an 80 percent survival rate among all cancers with Essiac treatment. This claim has never been backed by records or scientific study.

Despite its secretive history, the herbs in Essiac may offer some health benefits.

Homemaker's Magazine article with Rene Caisse
Homemaker's Magazine article on Rene Caisse from 1977.

What are the Ingredients and Benefits of Essiac Tea?

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 have shown anti-cancer effects in test tube and rat studies. But these roots also contain carcinogenic compounds that cause and promote cancer.
  • 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. The study found Essiac 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.

What Are the Side Effects of Essiac Tea?

Reported side effects of drinking Essiac tea include:

  • Nausea
  • Vomiting
  • Frequent urination
  • Increased bowel movements
  • Swollen glands
  • Headaches
  • Flu-like symptoms
  • Skin blemishes Mesothelioma Guide

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What Drugs Interact with Essiac?

The following drugs may negatively interact with the ingredients of Essiac tea:

  • Diuretic drugs
  • Diabetic drugs
  • Birth control pills
  • Hormone replacement drugs
  • Drugs that affect the kidneys and liver
  • DX-8951f (experimental chemotherapy drug)

Rene Caisse discusses Essiac tea.

Secret Recipe Brews Controversy

The origins of the recipe 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.

The secrecy of the recipe and preparation became a road block to scientific research and a source of controversy in later investigations.

Clinic Closed by Canadian Government

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 closed the clinic in 1941, Cassie continued to provide Essiac to cancer patients from her home.

Unpublished Clinical Trials

During the 1960s and 1970s, 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. With its inclusion, Caisse stopped providing injections.

Secret Recipe Sold

In 1977, a year before her death, Caisse sold the original, four-ingredient recipe for Essiac 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.

Promoters Discourage Traditional Treatment

Some promoters of Essiac say it should not be taken alongside traditional cancer treatments such as chemotherapy.

If cancer patients take Essiac as a first-line treatment, they run the risk of their cancer progressing to the point that traditional cancer treatment will no longer be effective.

Dr. Andrew Weil, a widely known supporter of natural medicine issued a warning about Essiac.

Dr. Andrew Weil

“Some 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.

Nonhuman studies have found evidence that Essiac both slows and promotes the growth of different cancers. Some studies found Essiac had no positive or negative impact on cancer.

  • Mid-1970s: A study conducted by Memorial Sloan Kettering Cancer Center (MSKCC) tested Essiac on mice with cancer. It found Essiac did not boost the immune system or impact cancer growth.
  • 1980s: MSKCC continued testing Essiac on animals with cancer. They conducted 17 studies in the 1980s and found no anti-cancer effect with Essiac.
  • 1983: The National Cancer Institute tested Essiac in mice with leukemia and found no anti-cancer effect. High doses of Essiac killed test animals in this study.
  • 2004: In a study published in Oncology Reports, Essiac slowed the growth of certain leukemia and breast cancer cells in test tubes.
  • 2004: Another 2004 study published in The Journal of Alternative and Complementary Medicine reported Essiac slowed prostate cancer cell growth in test tubes.
  • 2006: A study published in Breast Cancer Research and Treatment showed Essiac stimulates breast cancer growth.
  • 2007: A study published in Nutrition and Cancer found Essiac had no effect on prostate cancer cells.

Evidence on Essiac as a Cancer Cure Is Anecdotal

The claims that Essiac cures cancer are anecdotal, meaning self-reported and not proven by research. Scientific research has not found evidence that Essiac can cure cancer. But research has found it high in antioxidants.

  • A 2006 study published in the Journal of Ethnopharmacology shows Essiac contains antioxidants that protect against DNA damage. Antioxidants also help to counteract the effects of aging and exposure to toxins such as asbestos.
  • A 2007 study published in Anticancer Research reported Essiac has greater antioxidant properties than red wine, green tea and cocoa.

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

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

The FDA has not approved Essiac or Flor-Essence to treat cancer or any other medical condition. Companies sell Essiac and Flor-Essence as herbal dietary supplements, which the FDA does not regulate.

Consumption of Essiac is unlikely to cause serious side effects among people with mesothelioma when used as directed. Report any changes in your health to your doctor after taking herbal supplements.

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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.

Walter Pacheco, Managing Editor at
Edited by

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Last Modified September 10, 2019

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