What Is Reishi Good For? What the Trials Measured

Reishi (Ganoderma lucidum) has been tested in people for fatigue, immune markers, blood sugar, cholesterol and as an add-on in cancer care: in 132 patients with neurasthenia, 5.4 g a day of a reishi polysaccharide extract for eight weeks cut a fatigue score by 28% against 20% on placebo; in 398 people with type 2 diabetes or cardiovascular risk factors, 1.4 to 3 g a day for 12 to 16 weeks left HbA1c, cholesterol and weight unchanged; immune-cell counts rose in one healthy-volunteer trial and did not move in another; and the 2016 Cochrane review of reishi in cancer found five trials, none recording survival.^{1, 3, 5, 6, 7} No trial has measured sleep, memory or anxiety in otherwise healthy adults, and no mushroom holds an authorised health claim in Great Britain. This is the reishi evidence page of do mushroom supplements work?; side effects, the liver case reports and who should avoid it are in how you feel after taking reishi.

What is reishi good for? What the trials measured

Reishi is a hard, glossy, reddish-brown bracket fungus, lingzhi in China, too woody to eat as food, so it is taken as a hot-water decoction, a powder or an extract. Put "what is reishi good for?" to the trial record rather than to a label and the answer is a short list: fatigue in two trials, immune-cell counts in one of two, physical fitness in one fibromyalgia trial, and nothing for blood sugar, cholesterol, weight, mood or quality of life where those were measured. For sleep, memory, anxiety and stress there is no placebo-controlled trial in otherwise healthy people. Each result below carries its n, dose and duration, because a result from 5.4 g of extract says nothing about a 500 mg capsule.

What does reishi do for the brain?

No human trial has measured cognition, memory, neuroinflammation, brain plaque or mood as a primary outcome with reishi. The "neuroinflammation", "neuron-protecting", adrenal and cortisol claims come from laboratory and animal work. The nearest human data are secondary outcomes. In the 48-patient fatigue pilot in breast cancer, anxiety and depression scores were lower on reishi at four weeks, with no placebo for comparison.⁴ In women with fibromyalgia, six weeks of 6 g a day did not change happiness, depression, life satisfaction or quality of life against placebo.¹⁰ Among mushrooms, lion's mane has most of the placebo-controlled cognition trials, in older adults with mild impairment; reishi has none. So anyone taking reishi for anxiety or memory is outside what has been tested. The cortisol and stress trials that exist are of ashwagandha: does ashwagandha lower cortisol and stress, and what ashwagandha does for the brain.

Can reishi improve energy or fatigue?

Fatigue is where reishi has its best-designed result. Tang and colleagues randomised 132 Chinese patients with neurasthenia, a diagnosis of persistent tiredness and poor concentration, to 1,800 mg of a reishi polysaccharide extract three times a day (5.4 g a day) or placebo for eight weeks. In the 123 assessed, the sense-of-fatigue score fell by 28.3% on reishi and 20.1% on placebo, and clinician-rated severity by 15.5% against 4.9%.³ A 2012 pilot gave 48 women with breast cancer on endocrine therapy reishi spore powder for four weeks and recorded better fatigue scores and lower TNF-alpha and IL-6, two inflammation markers; it had no placebo.⁴ In 64 women with fibromyalgia, 6 g a day of micro-milled reishi for six weeks improved aerobic endurance, flexibility and walking speed; a carob comparator did not.⁹ None of these groups was a healthy adult feeling tired, and the Great Britain register lists reishi's claim "stimulates the body in exhaustion" as non-authorised because "physical well-being" was judged not sufficiently defined.¹² An absent claim is a statement about the register, not proof of no effect.

Is reishi good for immunity? What the immune-marker trials measured

In the laboratory, reishi beta-glucans bind to receptors on immune cells. In people, the measured changes are in cell counts. In an 84-day placebo-controlled trial of healthy adults aged 18 to 55, a daily reishi beta-1,3/1,6-glucan raised CD3+, CD4+ and CD8+ T-cell counts, natural-killer cell counts and activity, and serum IgA.⁵ In a four-week crossover trial of 18 healthy adults, 1.44 g a day of encapsulated reishi changed no immune, inflammation, antioxidant or DNA-damage marker.⁶ No reishi trial has measured an infection: nobody has counted colds, flu days or antibiotic courses against placebo. The register rejects every immune claim for mushrooms and for yeast beta-glucan, so a marker change stays a marker change.¹²

Does reishi lower blood sugar or cholesterol?

This is reishi's clearest answer, and it is a null. The 2015 Cochrane review pooled five randomised trials, 398 participants with type 2 diabetes or cardiovascular risk factors, taking 1.4 to 3 g of reishi a day for 12 to 16 weeks. HbA1c changed by -0.10% (95% confidence interval -1.05 to 0.85), total cholesterol by -0.07 mmol/L (-0.57 to 0.42) and LDL by +0.02 mmol/L; body mass index did not change.⁷ The same group then randomised 84 people with type 2 diabetes and metabolic syndrome to 3 g a day of reishi, with or without cordyceps, or placebo for 16 weeks: HbA1c differed by 0.13% (-0.35 to 0.60), fasting glucose by 0.03 mmol/L, and adverse events were no more frequent than on placebo.⁸ A 2025 pooled analysis of 17 trials and 971 participants, at 200 to 11,200 mg a day for one to 24 weeks, found no change in cholesterol, glucose or blood pressure and rated the certainty very low; the one exception is a 12-week trial of 110 people with raised lipids taking reishi spore oil, a different preparation, which reported lower total cholesterol, triglycerides and LDL.^{13, 14} So "reishi lowers blood sugar" and "reishi lowers cholesterol" have been tested at supplement doses and not found.

Does reishi help you sleep?

Reishi's reputation as a sleep mushroom is traditional: five PubMed searches for reishi and sleep in people without another condition found no placebo-controlled trial, and none of the fatigue or fibromyalgia trials recorded sleep. Animal studies measured sleep time, the source of the "calming" descriptions. Stress: no cortisol measurement in people exists.

What does the Cochrane review say about reishi and cancer?

Reishi's history as an add-on in cancer care in China and Japan is real, and so is what the trials show. The 2016 Cochrane review found five randomised trials of reishi preparations in cancer patients. None recorded long-term survival; the outcomes were tumour response, natural-killer cell activity, T-cell subsets and a quality-of-life scale, the methodological quality was "generally unsatisfying", and only one trial reported adverse events.¹ A 2023 systematic review of 39 clinical studies of 12 mushroom preparations in cancer found survival signals for two other preparations and none for reishi.² Reishi is not a cancer treatment. Anyone receiving chemotherapy, immunotherapy or hormone therapy asks their oncology team before taking any mushroom supplement, because reishi is taken for its effect on immune markers and that combination has not been studied.

What form of reishi did the trials use?

Almost every trial used the fruiting body, the bracket itself: a polysaccharide extract for fatigue, micro-milled powder in fibromyalgia, encapsulated powder in the crossover trial, spore powder in the cancer pilot. A label that states the part used, the extraction (hot water for beta-glucans, alcohol for triterpenes, "dual" for both) and a beta-glucan percentage tells you more than a 10:1 ratio, and quality varies: of 19 reishi supplements bought in the United States, only five matched their labels for triterpenes and polysaccharides.¹¹ Reishi mycelium, the root-like network often grown on grain, is different in law: EU consultation documents record the fruiting body as eaten before May 1997 and so not a novel food, and dehydrated reishi mycelium powder as a novel food needing authorisation. Great Britain applies the same test under its retained novel-food regulation, so the GB position is inferred from those documents rather than from a published FSA ruling. The Advertising Standards Authority adds that there are no authorised claims for mushrooms themselves. Three published liver-injury cases involved reishi powder; the safety page sets them out.

Frequently asked questions

What is the main benefit of reishi?

Measured in people, fatigue: a 28% fall in a fatigue score against 20% on placebo in one 132-person, eight-week trial at 5.4 g a day of extract.³

Is reishi mushroom good for anxiety?

Untested as a primary outcome: lower anxiety scores in a 48-patient pilot without a placebo, no change in a placebo-controlled fibromyalgia trial.^{4, 10}

What are reishi and cordyceps good for?

One supplier-funded trial combined them: 3 g a day with cordyceps changed no glucose measure in 84 people; what cordyceps does for the body has its own trials.⁸

How much reishi did the trials use?

1.4 to 3 g a day for 12 to 16 weeks, 5.4 g of extract a day for eight weeks, 6 g a day for six weeks; weight did not change in any of them, and no trial has measured belly fat.^{3, 7, 9}

Is reishi a psychedelic?

No. Its triterpenes and polysaccharides are not psychoactive and no trial reported intoxication; does lion's mane get you high? covers both mushrooms.

Sources

1. Jin X, et al. Ganoderma lucidum (Reishi mushroom) for cancer treatment. Cochrane Database of Systematic Reviews, 2016. PubMed 27045603.
2. Narayanan S, et al. Medicinal mushroom supplements in cancer: a systematic review of clinical studies. Current Oncology Reports, 2023. PubMed 36995535.
3. Tang W, et al. A randomized, double-blind and placebo-controlled study of a Ganoderma lucidum polysaccharide extract in neurasthenia. Journal of Medicinal Food, 2005. PubMed 15857210.
4. Zhao H, et al. Spore powder of Ganoderma lucidum improves cancer-related fatigue in breast cancer patients undergoing endocrine therapy: a pilot clinical trial. Evidence-Based Complementary and Alternative Medicine, 2012. PubMed 22203880.
5. Chen SN, et al. Evaluation of immune modulation by beta-1,3;1,6 D-glucan derived from Ganoderma lucidum in healthy adult volunteers, a randomized controlled trial. Foods, 2023. PubMed 36766186.
6. Wachtel-Galor S, et al. Ganoderma lucidum ("Lingzhi"), a Chinese medicinal mushroom: biomarker responses in a controlled human supplementation study. British Journal of Nutrition, 2004. PubMed 14756912.
7. Klupp NL, et al. Ganoderma lucidum mushroom for the treatment of cardiovascular risk factors. Cochrane Database of Systematic Reviews, 2015. PubMed 25686270.
8. Klupp NL, et al. A double-blind, randomised, placebo-controlled trial of Ganoderma lucidum for the treatment of cardiovascular risk factors of metabolic syndrome. Scientific Reports, 2016. Supplier-funded. PubMed 27511742.
9. Collado Mateo D, et al. Ganoderma lucidum improves physical fitness in women with fibromyalgia. Nutrición Hospitalaria, 2015. PubMed 26545669.
10. Pazzi F, et al. Ganoderma lucidum effects on mood and health-related quality of life in women with fibromyalgia. Healthcare, 2020. PubMed 33265969.
11. Wu DT, et al. Evaluation on quality consistency of Ganoderma lucidum dietary supplements collected in the United States. Scientific Reports, 2017. PubMed 28798349.
12. Department of Health and Social Care. Great Britain nutrition and health claims (NHC) register. gov.uk.
13. Jafari A, et al. The nutritional significance of Ganoderma lucidum on human health: a GRADE-assessed systematic review and meta-analysis. Food Science and Nutrition, 2025. PubMed 40510787.
14. Wang X, et al. Clinical evaluation of Ganoderma lucidum spore oil for triglyceride reduction. Nutrients, 2025. PubMed 40077714.