Ganoderma lucidum

Ganoderma lucidum (Curtis) P.Karst (Ganodermataceae) is a mushroom that grows on decaying trees. G. lucidum has been used in Asia for thousands of years to increase energy, stimulate the immune system, maintain health and promote longevity.¹ The colour of G. lucidum varies from orange and red through to brown and black, and the shape of the fruiting body can vary from a common mushroom shape to a branched (‘antler’) form.

Common names

Many, including: ganoderma; reishi, mannentake (Japan); lingzhi (China).

Preparations

Traditional preparations of G. lucidum include liquid dosage forms, such as teas and tonics. Contemporary preparations typically are formulated as fluid extracts, or capsules containing powdered dried extracts, or simply as powders, sometimes flavoured (with, for example, cocoa) for adding to beverages and foods. G. lucidum preparations are produced from different parts of the mushroom, including mycelia, spores and the fruiting body. Single- and multi-ingredient products (comprising herbal and non-herbal ingredients) are widely available.

Manufacturers’ claims

G. lucidum products are promoted/marketed by manufacturers for supporting the immune system and ‘heart health’, for helping improve blood glucose concentrations in people with diabetes or prediabetes, aiding sleep, supporting longevity, and as an adaptogen, for supporting physical and mental well-being, including helping the body cope with stress, among many other claims. Some products available for purchase online are promoted as having anti-inflammatory, antioxidant, antimicrobial and/or antitumour properties.

Active constituents

The main bioactive constituents of G. lucidum are considered to be the polysaccharides and triterpenoids.^2,3 The constituents are not uniform throughout the different parts of G. lucidum, for example, some compounds occur only in the spores. The polysaccharide constituents (which include a series of beta-glucans, among others) have anticancer, immunomodulatory, and hypoglycaemic effects in preclinical studies.³ The triterpenoid components, which include a series of ganoderic acids, have anticancer, hypoglycaemic, hypotensive, and cholesterol-lowering properties, and inhibit platelet aggregation.³ Other constituents include peptidoglycans and several bioactive proteins.

Efficacy

Many pharmacological effects, including anticancer, cholesterol-lowering, anti-diabetic, anti-obesity, hepatoprotective, immunomodulatory, anti-inflammatory, antibacterial, neuroprotective, antiepileptic, and other activities have been described for G. lucidum extracts and/or isolated constituents, or groups of constituents, following preclinical (in-vitro and/or animal) studies.²

Clinical research with preparations of G. lucidum has explored several of the activities reported in preclinical studies, particularly anticancer, cardioprotective and antidiabetic effects. However, at present, there is no definitive evidence for efficacy of G. lucidum in these or other conditions. A Cochrane systematic review included five randomised controlled trials (RCTs) of G. lucidum for the treatment of various cancers, and examined its impact on long-term cancer survival rates and quality of life.¹ The review concluded that G. lucidum could have synergistic potential with cancer chemotherapy and radiotherapy in patients with lung cancer, but that it is not known if this would improve long-term survival. Importantly, the review found no evidence to support the use of G. lucidum alone as a cancer treatment, as its antitumor effect was found to be negligible when used as a sole treatment. In addition, the methodological quality of the RCTs identified was poor and there was substantial heterogeneity among the included studies.¹

Another Cochrane systematic review included five RCTs of G. lucidum preparations, or a polysaccharide extract, for the treatment of pharmacologically modifiable risk factors of cardiovascular disease; three trials involved patients with type 2 diabetes mellitus and provided data suitable for analysis.⁴ No effect of G. lucidum was found on the primary endpoints: HbA1c; fasting blood glucose concentration; triglycerides and cholesterol profile; blood pressure.⁴

These systematic reviews included trials investigating any type of preparation (eg teas, powders, solid-dose forms) of G. lucidum and its polysaccharide constituents, originating from any of its parts (mycelium, stem, root, spore), and used at any dose and dosage. Both reviews found deficiencies in the quality of reporting of the trials.

Large, robust trials of well-characterised G. lucidum preparations are required; trial reports should follow standard reporting checklists, including providing comprehensive descriptions of G. lucidum preparations tested, including whether the product meets accepted standards for pharmaceutical quality.

Adverse effects

RCTs included in Cochrane systematic reviews of G. lucidum preparations provided very limited data related to safety aspects. One trial reported nausea and/or insomnia in three patients who received a multi-ingredient product containing G. lucidum extract.¹ Another trial reported an increase in anticipated mild gastrointestinal adverse effects (nausea, diarrhoea, and constipation) among participants taking G. lucidum, but this was reported as not being statistically significant.⁴ In the scientific literature, there are isolated reports of hepatotoxic reactions occurring in people who had been exposed to G. lucidum in single- or multiple-ingredient products. These cases include reports of deranged liver enzymes, cholestatic liver injury and fulminant hepatitis; however, causality has not been definitively established in these cases, and reports often lack comprehensive information on the products (and medicines) consumed.

There is a lack of reliable information on effects of G. lucidum preparations in children, pregnant and breastfeeding women; until further information is available, a cautious approach is to avoid use in these population groups. Also, due to the potential immunomodulatory effects of G. lucidum, it should probably be avoided in individuals with autoimmune diseases.⁵

Interactions

There is little published evidence about possible drug or food interactions with G. lucidum. In vitro, a methanol extract of G. lucidum inhibited the metabolism of lapatinib (a tyrosine kinase inhibitor, not available in New Zealand), but the clinical relevance of this is not clear. Given the range of pharmacological effects reported for G. lucidum – at least in preclinical studies – caution is advised in relation to use of G. lucidum by patients taking immunosuppressant, anticancer, antiplatelet, anticoagulant, antidiabetic, and/or antihypertensive medications.

Data availability

Data sharing is not applicable as no new data were generated or analysed for this article.

Conflicts of interest

JB is a co-author/co-editor of books on scientific aspects of herbal medicines and receives/has received royalties from Pharmaceutical Press, Elsevier, and SpringerNature/MacMillan Education.

Declaration of funding

This research did not receive any specific funding.