Reishi (Ganoderma lucidum): The “Mushroom of Immortality” in the Light of Research

Reishi, or lingzhi (Ganoderma lucidum), is one of the most famous medicinal mushrooms in the world. In traditional Chinese and Japanese medicine it has been called the “mushroom of immortality” for centuries, and today you will find it in capsules, powders, extracts and teas. Does modern science back up its reputation? Below I have gathered what reviews of clinical studies say, with links to the sources so that you can check them yourself.

What reishi is

Reishi (Ganoderma lucidum) is a tough, woody mushroom with a shiny cap that looks as if it has been varnished, growing on the trunks and roots of broadleaved trees. In the wild it occurs mainly in warm, humid regions of Asia, and in Poland it is a very rare species. According to a 2015 Polish scientific review^[5] it is strictly protected in Poland, so do not pick it in the forest. Fruiting bodies from cultivation are used for medicinal purposes.

Reishi is not suitable for eating like an ordinary mushroom: it is hard and very bitter. It is usually taken as powdered fruiting body, a water or alcohol extract, or capsules containing an extract. The names Ganoderma lucidum and Ganoderma lingzhi are sometimes used interchangeably in publications and on packaging.

What it contains

The potential effects of reishi are attributed mainly to compounds from two groups: polysaccharides (including beta-glucans), which are thought to influence the immune system, and triterpenes, which give the mushroom its bitter taste. It also contains sterols, nucleotides and phenols. The composition depends on the strain, the growing method, the part of the mushroom (fruiting body, mycelium, spores) and the extraction method, so two supplements labelled “reishi” can be very different.

How strong is the evidence?

Online, reishi is often described as a miracle cure for everything. Yet the best independent reviews (Cochrane) paint a more cautious picture: the effects are small or unconfirmed, and the studies are often small and of poor quality. In laboratory and animal studies reishi shows many interesting properties, but results from a test tube or a mouse do not always translate to humans. Below I discuss what has been studied in people.

Immunity and cancer

This is the most common reason people turn to reishi. A 2016 Cochrane review^[1] included five randomised trials involving 373 people from China. Its conclusions were as follows:

• adding reishi to chemotherapy or radiotherapy was associated with a slightly higher response rate, but the mushroom on its own, given without standard treatment, did not shrink tumours,
• in patients taking reishi some immune markers rose slightly (CD3, CD4 and CD8 lymphocytes), while NK-cell activity changed only marginally,
• four of the studies pointed to improved quality of life,
• none of the studies reported survival data, so it is not known whether reishi prolongs patients’ lives.

The review authors concluded that the evidence is insufficient to recommend reishi as a cancer treatment. At most, it could be considered as a complement to standard therapy, agreed with the oncologist, and never as a replacement for it. The quality of the studies was rated as unsatisfactory.

Heart, cholesterol and blood sugar

Another Cochrane review (Klupp et al., 2015)^[2] examined whether reishi helps with risk factors for heart disease. The analysis included three trials in 157 people with type 2 diabetes who took 1.4 to 3 g of reishi a day for 12 to 16 weeks. No significant effect was found on:

• blood pressure,
• total cholesterol, LDL cholesterol and triglycerides,
• glycated haemoglobin (HbA1c) and fasting glucose.

The results for blood sugar after meals were inconclusive. The authors concluded that the current evidence does not support using reishi to treat cardiovascular risk factors in people with type 2 diabetes. If you have diabetes or high blood pressure, reishi will not replace your medication.

Fatigue, mood and the large intestine

Besides immunity, reishi has been studied for fatigue and well-being. The results are promising, but these are mostly small studies:

• Neurasthenia. In a randomised, double-blind, placebo-controlled trial, 132 patients with neurasthenia (a condition with fatigue, irritability and aches and pains) took a reishi polysaccharide extract (Ganopoly) or a placebo for 8 weeks. Fatigue fell by 28.3% in the reishi group compared with 20.1% in the placebo group, and 51.6% of participants achieved more than minimal improvement compared with 24.6% on placebo.^[6]
• Fatigue after breast cancer. In a pilot study, 48 breast-cancer patients on hormone therapy who suffered from fatigue took reishi spore powder for 4 weeks. In the study group, measures of fatigue and physical well-being improved, there was less anxiety and depression, and TNF-α and IL-6 levels were lower. No serious adverse effects were recorded. The authors stress that this was a pilot study.^[7]
• Colorectal adenomas. In a Japanese controlled study without random assignment, taking a water extract of reishi mycelium for 12 months was associated with a reduction in the number of adenomas (precancerous lesions) by an average of 0.42, while in the control group their number rose by 0.66. The total size of the lesions decreased by 1.4 mm, while in the control group it increased by 1.7 mm.^[8]

There are also reports of antioxidant effects: reishi performs well in the laboratory, but there is no hard evidence that this translates into health benefits in humans. All the studies listed were small, and some were not randomised, so larger, better-designed trials are needed.

Forms and doses

The dose depends on the form of the product. According to the LiverTox database^[3], typical intake is around 500 mg to 3 g a day, and clinical studies have used doses such as 1.4 g a day. However, the content of active ingredients varies between products: raw fruiting-body powder, a water extract and a concentrated extract have completely different strengths. Always stick to the dose on the package, do not increase it on your own and check which form you are buying. Choose products that clearly state the species, the part of the mushroom and the amount of extract, ideally from reputable manufacturers.

Safety and side effects

In short clinical studies reishi was usually well tolerated. The most commonly reported complaints were mild, such as nausea, diarrhoea or constipation; in the Cochrane review on the heart there were slightly more adverse events than in the placebo group, although the difference was not statistically significant and the symptoms were not serious.

Particular attention is paid to the liver. LiverTox rates reishi as a possible, rare cause of liver injury (category D).^[3] Isolated cases have been described, usually after 1 to 2 months of use, ranging from a mild rise in liver enzymes to severe hepatitis, and in one case from Thailand ending in death. The quality of these reports is limited, as other causes, such as other herbs, medicines or alcohol, were often not ruled out. After stopping the product, the liver returned to normal within 1 to 3 months in most patients. A 2023 case report (a man taking large amounts of reishi powder together with alcohol)^[4] highlights that combining it with alcohol may be particularly risky.

If you develop severe tiredness, dark urine, jaundice or pain under the right ribs while taking reishi, stop the product and see a doctor.

Who should be careful

The recommendations below are precautionary. For some of them good studies are lacking, so it is safer to talk to a doctor before using reishi:

• pregnant and breastfeeding women: there are no safety data,
• people with liver disease and those who drink alcohol regularly,
• people with bleeding disorders or taking anticoagulants,
• people preparing for surgery,
• people with low blood pressure or taking medication for high blood pressure and diabetes, to avoid overlapping effects,
• people with cancer who are undergoing treatment: tell your oncologist about every supplement.

Reishi is not a medicine, and dietary supplements are not subject to the same controls as medicines. Do not give it to children.

Growing reishi in brief

Reishi can be grown on hardwood logs or in bags of sawdust, in a warm, humid room. The cycle is long and takes patience, and the result is hard, woody fruiting bodies which, once dried, are used to make infusions. I described similar principles for inoculating logs in the article on shiitake (in Polish), and you can read about another medicinal mushroom that can be grown on a plot in the article on lion’s mane.

Frequently asked questions

Can reishi be eaten like ordinary mushrooms?

No. It is too hard and bitter. It is used as an infusion (simmered for a long time), a powder or an extract.

Does reishi cure cancer?

There is no evidence for this. Studies suggest at most some benefits as a complement to standard therapy, and always after consulting a doctor.

How long can it be taken?

Studies usually lasted from a few weeks to a few months. There are no good data on use over many years, so it is worth taking breaks and having your liver function checked with longer use, especially if you have liver disease.

Summary

Reishi is a fascinating mushroom with a long tradition, but modern science does not yet confirm most of the benefits attributed to it. The best reviews point to possible small supportive effects on immunity and quality of life in patients, and small studies suggest relief from fatigue and a possible effect on colorectal adenomas, with no effect on blood pressure, cholesterol or blood sugar. If you decide to take it, choose reputable products, stick to the doses and consult your doctor, especially if you have health conditions or take medication.

Sources

1. Jin X., Ruiz Beguerie J., Sze D.M., Chan G.C. (2016). Ganoderma lucidum (Reishi mushroom) for cancer treatment. Cochrane Database of Systematic Reviews. DOI.
2. Klupp N.L. et al. (2015). Ganoderma lucidum mushroom for the treatment of cardiovascular risk factors. Cochrane Database of Systematic Reviews. Cochrane summary.
3. LiverTox (NIDDK, National Institutes of Health): Lingzhi / Reishi (Ganoderma).
4. Ganoderma lingzhi (Reishi Mushroom)-Induced Acute Liver Injury in the Setting of Alcohol Use: A Case Report and Review of the Literature (2023). PMC10599861.
5. Siwulski M., Sobieralski K., Golak-Siwulska I., Sokół S., Sękara A. (2015). Ganoderma lucidum (Curt.: Fr.) Karst. – właściwości prozdrowotne. Praca przeglądowa. Herba Polonica (in Polish). DOAJ.
6. Tang W. et al. (2005). A randomized, double-blind and placebo-controlled study of a Ganoderma lucidum polysaccharide extract in neurasthenia. Journal of Medicinal Food 8(1):53–58. DOI: 10.1089/jmf.2005.8.53.
7. Zhao H., Zhang Q., Zhao L., Huang X., Wang J., Kang X. (2012). 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. PubMed.
8. Oka S., Ito M. (2010). A Water-soluble Extract from Culture Medium of Ganoderma lucidum Mycelia Suppresses the Development of Colorectal Adenomas. Hiroshima Journal of Medical Sciences 59(1):1–6. Hiroshima Univ..

This article was originally written in Polish and has been translated into English.

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This article comes from my blog Laboratorium Natury (“Nature Lab”), where I write about my garden plot in Poland and a more self-sufficient life. Full version with photos: https://jaworznia.pl/en/2026/10/28/reishi-ganoderma-lucidum-mushroom-of-immortality/