An April 2012 review published in “Journal of Traditional and Complementary Medicine” stated that there are no apparent side effects recorded with the use of reishi mushrooms. However, a study published in the July 2008 issue of “Canadian Journal of Clinical Pharmacology” demonstrated that while the use of G. lucidum, or reishi mushrooms, in cancer therapy stimulated immune cells, large doses were toxic to these same immune cells. The American Herbal Products Association’s Botanical Safety Handbook lists a summary of known adverse reactions, such as rare allergic reactions to the mushrooms. According to this review, reishi mushrooms appear well tolerated, but there is little data on their long-term safety — as one study links potential symptoms of dizziness, dry mouth and abdominal upset with 3 to 6 months of continual use.
Dietary supplements are not regulated by the U.S. Food and Drug Administration. This means that supplement companies do not need to provide proof a given supplement contains active components or that the dietary supplements provide any benefit at all. The article in “Integrative Cancer Therapies” indicated that some of the supplements tested were low in biologic activity and that consumers should be cautious when choosing a supplement. In addition, the extract of reishi mushrooms is often combined with other herbal compounds, making it difficult to determine which ingredient is responsible for any noted benefits.
Warnings and Precautions
Consult with a doctor before beginning any alternative medicine supplement. Reishi mushrooms can interact with certain medications, and for those on blood thinning medication, reishi mushrooms may increase the risk for bleeding. Reishi mushrooms have the potential to interfere with cancer chemotherapy drugs. Women who are pregnant or breastfeeding should speak with a physician before taking any supplements. There are no specific recommendations on the use of reishi mushrooms for medicinal purposes or for the treatment of any condition. More high-quality human studies are needed to know if supplementation from reishi mushrooms, and at what dosage, is safe and beneficial for human health.