Reishi Mushroom: What the Evidence Shows on Health Benefits and Safety

What Is Reishi Mushroom?

Reishi mushroom (Ganoderma lucidum), known in traditional Chinese medicine as Ling Zhi ("Spirit Plant") and long revered as the "Mushroom of Immortality," has been used in East Asian wellness traditions for over 2,000 years. It grows on hardwood trees in humid, temperate climates and is distinguished by its distinctive kidney-shaped cap with a glossy, reddish-brown surface.

What makes Reishi scientifically interesting — and distinct from marketing claims about most supplements — is the depth of its research base. Reishi has been the subject of multiple Cochrane systematic reviews, randomized controlled trials, and comprehensive phytochemistry analyses. The picture that emerges is of a multi-mechanistic botanical with well-characterized active compounds and reassuring short-term human data, alongside important gaps in long-term safety data and in clinical evidence.

This article reviews what the peer-reviewed literature actually shows across Reishi's primary areas of research: immune modulation, antioxidant and anti-inflammatory activity, cardiovascular and metabolic effects, and its role as an adaptogenic stress support.

The Active Compounds: β-Glucans and Triterpenoids

β-Glucans — Immune Architecture

The most clinically studied compounds in Reishi are its polysaccharides — primarily β-1,3/1,6-glucans. These complex carbohydrates interact directly with immune receptors (particularly Dectin-1 and toll-like receptors) on macrophages, dendritic cells, and natural killer cells, triggering a cascade of immune activation and regulation.

β-glucans are described as immunomodulatory, meaning they can influence immune activity in laboratory studies. How Reishi affects people with autoimmune conditions, or people taking immunosuppressant medicines, has not been well studied⁶, so those groups should check with their doctor before use.

Triterpenoids — Anti-inflammatory and Adaptogenic

Reishi contains over 140 distinct triterpenoid compounds — particularly ganoderic acids — that are unique to Ganoderma species and not found in other medicinal mushrooms. These compounds have been reported to have anti-inflammatory and adaptogenic properties, mostly in laboratory research⁶. They are responsible for Reishi's characteristic bitter taste and much of its adaptogenic character — the ability to help the body modulate its response to physiological and psychological stress.

Immune System Support: The Strongest Evidence

Randomized Controlled Trial — T-Cell and NK Cell Activation

The strongest human clinical evidence for Reishi's immune effects comes from a 2023 randomized controlled trial published in Foods (Chen et al.), which evaluated β-1,3/1,6-glucan derived from Ganoderma lucidum in healthy adult volunteers.

The trial reported significant increases in multiple immune cell populations in the Reishi group compared to placebo:

• CD3+ T-lymphocytes — total T-cell population supporting both cellular and humoral immunity
• CD4+ helper T-cells — the coordinators of immune response, directing other immune cells
• CD8+ cytotoxic T-cells — responsible for directly eliminating infected or abnormal cells
• Natural Killer (NK) cells — innate immune defenders that identify and destroy threatening cells without prior sensitization

The trial reported changes in immune cell counts, immunoglobulin A levels and natural killer cell activity in healthy adults over 84 days. These are laboratory markers, and the published summary does not report whether they lead to fewer infections or other health benefits, so the practical benefit is not yet established¹.

Cancer Adjunct Therapy — Cochrane Review

A 2016 Cochrane systematic review (Jin et al.) examined Reishi mushroom supplementation in cancer patients receiving conventional therapy. The review pooled five trials, and its authors described the methodological quality of those trials as generally unsatisfying. Alongside standard treatment, Reishi was associated with modest increases in CD3, CD4 and CD8 cell percentages (about 2 to 4 percentage points), and four studies reported relatively improved quality of life. No trial recorded long-term survival⁴.

Reishi should not be considered a replacement for established cancer therapies. The reviewers did not find sufficient evidence to justify Reishi as a first-line cancer treatment and advised that use of Reishi extract should be judicious⁴. Anyone considering Reishi alongside cancer treatment should discuss with their oncologist first, as individual circumstances vary significantly.

Antioxidant and Anti-inflammatory Activity

Oxidative stress and chronic low-grade inflammation are underlying drivers of most age-related chronic conditions. Reishi mushroom has one of the most extensively studied antioxidant profiles among medicinal mushrooms.

A comprehensive 2018 review published in Molecules (Cör et al.) synthesized evidence across Reishi's bioactive activities and documented significant antioxidant, antimicrobial, antitumor, antifungal, antiviral, and anti-inflammatory effects. The mechanisms involve both the triterpenoid compounds (which inhibit key inflammatory signaling pathways, including NF-κB) and the polysaccharides (which support antioxidant enzyme systems).

A 2023 review in Food Function (Swallah et al.), covering Reishi research from 2010–2022, further confirmed these findings and highlighted Reishi's potential to support cellular protection against oxidative damage — particularly relevant as an adjunct to the oxidative load of modern lifestyle stress.

Cardiovascular and Metabolic Effects: Where Evidence Is Mixed

Reishi is frequently marketed for cardiovascular and blood sugar benefits. It is worth being precise about what the evidence actually shows here — including where it is limited.

A 2015 Cochrane systematic review (Klupp et al.) specifically examined Reishi's effects on cardiovascular risk factors in type 2 diabetes patients and found insufficient evidence to confirm significant effects on blood glucose, lipid profiles, or blood pressure at the time of review. This is the rigorous standard, and intellectual honesty about mixed evidence is more useful than overclaiming.

More recent research has added nuance. A 2021 review published in Pharmaceutical Biology (Chan et al.) described blood-sugar-lowering effects in people with type 2 diabetes or high blood glucose as the most compelling evidence so far, but called the overall clinical evidence inconsistent and said larger controlled studies are needed³.

The current evidence does not support Reishi as a primary intervention for cardiovascular disease or diabetes management, and those conditions require physician-directed treatment². Because blood-sugar-lowering effects have been reported in some studies³, people taking diabetes medicines should check with their prescriber or pharmacist before adding Reishi.

Adaptogenic and Stress Support Properties

One of Reishi's most compelling yet least-discussed research areas is its adaptogenic character — the ability to help the body modulate its physiological stress response. The triterpenoid compounds in Reishi have demonstrated activity on the HPA (hypothalamic-pituitary-adrenal) axis, the central stress regulation pathway that governs cortisol production.

This positions Reishi alongside Ashwagandha and Rhodiola as a legitimate evidence-based adaptogen — with the added benefit of its immune-modulating properties, which Ashwagandha and Rhodiola do not share. For individuals experiencing stress-related immune suppression (a well-documented phenomenon), Reishi's dual action on stress pathways and immune function is particularly compelling.

Safety Profile

In short clinical trials, Reishi has generally been well tolerated. A 12-week trial in healthy adults found no significant change in kidney or liver blood tests¹, and a Cochrane review of five trials in people with cancer reported no major toxicity⁴. However, a 2021 review notes that clinical data on long-term use, interactions with foods and drinks, and teratogenicity (harm to a developing baby) are missing⁶, and case reports describe liver injury in people taking Reishi (see the cautions below).

• Generally well tolerated in the short trials reviewed^1,2,4
• Long-term (chronic use) human safety data is lacking⁶
• Mild side effects such as nausea and insomnia were reported in one cancer trial⁴. In a Cochrane review of trials in type 2 diabetes, adverse events were reported more often with Reishi than with placebo over four months, although the difference was not statistically significant and the events were not serious²
• No major toxicity was reported in the trials reviewed^1,2,4. Separately, case reports describe liver injury, including one fatal case, in people taking Reishi products^8,9,10

Important cautions to be aware of:

• Liver: Case reports describe liver injury associated with Reishi (lingzhi) products. Reports from Hong Kong and Thailand describe liver toxicity after taking a Reishi formulation or powder, one of them fatal (fulminant hepatitis), and the authors note that the patients had also taken other therapeutic agents^8,9. A 2023 report describes acute hepatitis, which resolved within two weeks, in a man who had consumed Reishi powder and alcohol¹⁰. Because these are isolated case reports, how often this happens is unknown. People with liver disease, and anyone who drinks alcohol or takes other medicines that can affect the liver, should check with their doctor before use, and anyone who notices signs of liver problems (such as yellowing of the skin or eyes) should seek medical advice.
• Blood thinners and surgery: In laboratory tests, a Reishi extract reduced platelet aggregation¹¹, but a 4-week trial in 40 healthy volunteers found no impairment of blood clotting or platelet function¹². We did not find studies of Reishi in people taking warfarin or antiplatelet medicines, so anyone taking these medicines, and anyone facing surgery, should speak to their doctor or pharmacist before use
• Immunosuppressant medications and autoimmune conditions: A trial in healthy adults found changes in immune cell measures with a Reishi β-glucan¹, and we did not find studies of Reishi in people taking immunosuppressants or with autoimmune disease. Those groups (including organ transplant recipients) should consult their doctor before use
• Mushroom allergy: Anyone with known mushroom or mold allergies should avoid Reishi
• Pregnancy and nursing: Insufficient safety data; avoid during pregnancy