Reishi has been recognized as one of the most powerful cancer fighting food worldwide. It has a long history of use in the treatment of cancer and is credited with many cases of spontaneous remission.
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There are many published studies on its anti-cancer effects in various human and mouse tumor cell lines. Although the evidence from well-designed clinical trials is not available yet, there is considerable evidence to support the immune stimulating activities of Reishi through increased cytokine production and enhancement of immunological effector cells according to Herbal Medicine: Biomolecular and Clinical Aspects. 2nd edition.

Reishi polysaccharide beta-glucan has the most profound impact on the immune system. The level of anti-cancer activity is related to its degree of branching and to solubility in water, with higher solubility and greater degree of branching being associated with higher activity. Ganoderic acid, a Reishi triterpene, also has significant anti-cancer properties. When Reishi was used as a single agent on metastatic cancer patients, significant enhancement of cellular immunity was noted with high plasma concentrations of interleukin-2 and interferon-gamma, and natural killer (NK) cell activity according to the article "A Phase I/II Study of a Ganoderma lucidum (Curt.: Fr.) P. Karst. Extract (Ganopofy) in Patients with Advanced Cancer".
Another study in advanced lung cancer showed improvement of total T cells and NK cells in 65% of patients taking Reishi extract.​
Research on Reishi & Cancer