Essiac, also marketed as flor essence and pitched as "the medicine man's cure for cancer", is an alternative cancer therapy invented from whole cloth by Rene Caisse around 1920 (the name is her surname reversed), claimed to have been a recipe derived from an Ojibwa medicine man.
As Cancer Research UK succinctly puts it: "There is no scientific evidence to show that Essiac can treat, prevent or cure cancer or any other serious illness in humans."
In 1977 Caisse gave the formula to a Canadian company, which attempted to commercialize the product but was unable to show any efficacy against cancer. Repeated laboratory tests showed that essiac failed to slow tumor growth and, in large enough 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 as a dietary supplement, which avoided the tedious necessity of showing any proof of effectiveness.
Essiac was investigated by Memorial Sloan-Kettering Cancer Center and NCI from the 1950s to the 1980s in animal models, and was found to have no real effect. While it showed some antioxidant and even cytotoxic properties in vitro it stimulated growth of human breast cancer cells both via estrogen receptor (ER)-dependent and ER-independent pathways. Individual case reports claim benefit, but larger studies (e.g., in breast cancer patients) show no benefit, making it more likely that the individual reports are merely coincidence based on the natural variability of cancer.
Essiac consists of parts of 4 herbs that grow wild in Ontario, Canada:
- Greater burdock (Arctium lappa) — root
- Slippery elm (Ulmus rubra, a.k.a, U. fulva) — inner bark
- Sheep sorrel (Rumex acetosella')
- Indian rhubarb (Rheum officinale) — root