For thousands of years, mushrooms have been used worldwide for their medicinal properties, especially in Asia. The earliest known reference for medicinal mushrooms was around 3,000 BCE. The largest known organism in the world is a honey mushroom mat in eastern Oregon which is 890 hectares (almost 2,500 acres!) and more than 2,000 years old. There are an estimated 150,000 mushroom species on earth, but thus far, only about 270 species have been reported to have medicinal properties.

Mushrooms have a multitude of medicinal actions including anti-inflammatory, anti-microbial, anti-diabetic, cardio and liver-protective, immune-modulatory and anti-cancer properties. Mushrooms have been studied for their anti-cancer affects in multiple types of cancer, with the majority of the studies on breast cancer. A 2021 systematic review of 17 observational studies found that higher mushroom consumption was associated with a lower risk of breast cancer. Most of the research so far are cell line studies, animal tumor models and a few clinical/human studies.

I am going to touch on three commonly studied mushrooms for breast cancer: turkey tail, reishi and maitake. Many of the studies use polysaccharide extracts such as ß-Glucan, PSK, and D-Fraction. These extracts exhibit immunomodulatory effects as well as tumoricidal and antiproliferative activities in cancer patients through the stimulation of natural killer cells, neutrophils, monocytes, macrophages and T-cells. Basically, these constituents can help the body activate the immune system to recognize and remove the tumor, in a BALANCED manner.

Trametes versicolor or coriolus versicolor (turkey tail). PSK, an extract of turkey tail, slowed down tumor growth when used alone, and increased cancer cell death in combination with trastuzamab, a HER-2 targeted monoclonal antibody.

Ganoderma lucidum (reishi). ß-Glucan isolated from reishi significantly improves survival post radiation in mice. Ganoderic acid A, another isolate, worked with cisplatin to increase breast cancer cell death. Reishi spore powder was found to significantly improve cancer related fatigue and quality of life in breast cancer survivors on endocrine (hormone blocking) therapy.

Grifolia frondosa (maitake). In mouse models, D-Fraction, a constituent of maitake, was able to slow tumor growth and reduce metastasis in triple negative breast cancer. In a 2009 Phase I/II clinic trial of post-menopausal breast cancer survivors, a ß-glucan extract showed immune balancing effects, not just immune-stimulatory effects.

Note that whole plants and fungi have hundreds of constituents working synergistically, so the exact mechanisms of action are not fully understood and are still being studied.

It is difficult to translate dosing from studies to human consumption as most of the studies don’t use the whole mushroom. In the small number of human studies, specific mushroom extracts were used in large doses, anywhere from 1-6 grams daily, which could be cost prohibitive. High quality mushroom supplements from trusted brands and distributors can be expensive. As mushrooms have immune modulatory affects, they may have interactions with other supplements and drugs that we do not yet know about.

Even with the increased interest in mushrooms as potential treatments for cancer, there still needs to be more research in this growing field.

Safety and sourcing notes: mushrooms can sequester heavy metals, so know where and how your mushrooms are grown. This should also go without saying, do not pick and eat strange mushrooms; many mushrooms look the same, and some can be lethal. Do not start a new supplement or medication without consulting a knowledgeable, qualified doctor.

Dr. Sonja Fung is a primary care naturopathic doctor with a focus on integrative cancer care and regenerative joint injections at Live Well Clinic in La Quinta. Her clinic offers B vitamin injections, IV nutrients, and functional lab testing for a personalized health plan. For more information, call (760) 771.5970 or visit www.livewellclinic.org.

References available upon request.