Key takeaways
- Reishi is heavily researched, but mostly in cells and animals.
- Human studies vary widely; reviews often find the evidence limited.
- Species naming and differing materials make studies hard to compare.
- The evidence doesn’t support specific claims about effects in people.
Reishi has been studied more than almost any other mushroom, yet the evidence is much harder to interpret than the volume suggests. This article explains why, walks through the main human trials and reviews, and sets out what can reasonably be concluded.
Why there is so much Reishi research
Reishi, known as lingzhi in China, has a cultural history stretching back around two thousand years. It appears in the Shennong Bencao Jing, one of China’s oldest botanical texts, and throughout Chinese art as a symbol of longevity and good fortune. See Reishi Through History and Traditional Culture.
That history, combined with two chemically distinct groups of compounds, triterpenes and polysaccharides, has made Reishi a favourite subject for laboratories, particularly in China, Japan, Korea and Taiwan. Reishi is also easy to cultivate, which makes research material readily available. See Reishi Compounds Explained and Triterpenes in Mushrooms Explained.
Why Reishi research is hard to interpret
The naming problem
For decades, the Reishi used in Asia was called Ganoderma lucidum, a name originally given to a European species. DNA work has since shown that much of the cultivated East Asian lingzhi is a different species, now often called Ganoderma lingzhi. Many studies labelled G. lucidum may therefore have used something else, and few studies confirmed their species with DNA testing. See Ganoderma Species Explained.
Different materials
Studies have used the fruiting body, the mycelium, spore powder, spore oil and proprietary polysaccharide preparations. These differ enormously in their chemistry. Triterpenes, for example, are concentrated in the fruiting body and spores, and are drawn out by alcohol rather than water. See How Reishi Is Extracted.
Poor characterisation
Many studies don’t report what their material actually contained, making it impossible to know whether two studies of “Reishi” tested anything alike.
The three tiers of evidence
Laboratory studies of individual triterpenes and polysaccharides are numerous, and animal studies have tested many extracts and fractions. As with all mushrooms, these don’t reliably predict effects in people. See In Vitro, Animal and Human Studies. Human trials exist, and because several have looked at the same outcomes, they have also been pooled in systematic reviews.
The human studies: a closer look
Several of the better-documented Reishi trials have looked at blood sugar, blood pressure and cholesterol, which makes them a useful case study in how the evidence changes as trials get larger and better controlled.
Gao et al., 2004. An early phase I/II study that enrolled 71 people with type 2 diabetes, using a proprietary Reishi polysaccharide product (Ganopoly) for 12 weeks. The researchers reported differences in blood sugar measures. The material was a concentrated polysaccharide preparation, not a whole-mushroom extract, and early-phase studies like this are designed to explore rather than confirm.
Wang et al., 2008 (Taiwan). A randomised, double-blind, placebo-controlled trial of 46 people with type 2 diabetes taking 3 g a day of a dry Reishi extract for 12 weeks. There were no changes in fasting blood sugar or HbA1c, the main long-term measure, though one measure during a meal test differed.
Chu et al., 2012. A double-blind, crossover trial of 23 people with borderline blood pressure or cholesterol, taking a Reishi product or placebo for 12 weeks. The researchers found no significant effect on blood sugar, blood pressure or cholesterol, although some insulin-related measures differed.
Klupp et al., 2016 (Australia). The largest and one of the best-designed trials: 84 people with type 2 diabetes and metabolic syndrome were randomised to Reishi, Reishi with Cordyceps, or placebo, at 3 g a day for 16 weeks. The Reishi treatments had no effect on any of the primary or secondary measures, and there was no overall increase in adverse events. This trial was run by an independent academic institute.
What the systematic reviews say
A 2015 Cochrane review, widely regarded as a gold standard for evidence summaries, pooled five placebo-controlled trials including 398 people with type 2 diabetes. It judged the overall quality of the trials to be poor, and concluded that the evidence does not support using Reishi to treat cardiovascular risk factors in this group. Participants taking Reishi were somewhat more likely to report adverse events, though these were not serious and the difference was not statistically certain. The review authors declared that some of them had run one of the included trials.
The pattern here is common across natural-product research: early, smaller studies, often of proprietary materials, report positive findings, while larger, independent, better-controlled trials tend to find smaller effects or none.
Safety
Reishi is generally well tolerated in trials. However, the US National Institutes of Health’s LiverTox database notes rare single reports of acute liver injury linked to Reishi, while cautioning that other causes were often not properly ruled out, and rates it only a possible rare cause. The best-known reports involved powdered Reishi products. In one case from Thailand, published in 2007, a patient who had taken traditionally boiled Reishi without problems developed fatal liver failure one to two months after switching to a powder, while also taking other medicines. Case reports cannot prove cause and effect, but they are a reason for care.
Anyone with a mushroom allergy should avoid Reishi. If you are pregnant, breastfeeding, taking medication or managing a health condition, speak to your GP or pharmacist before taking any mushroom supplement. Tinctures also contain alcohol.
What we can reasonably conclude
Reishi is a legitimate and active research subject with a remarkable cultural history and distinctive chemistry. But the better-designed human trials have mostly found little or no effect on the outcomes they measured, and the evidence doesn’t support specific claims about what Reishi products do in people. No health claims are authorised for Reishi in the UK.
What remains uncertain
- Which species many studies actually used.
- Which compounds, parts and preparations might matter in people.
- What amounts, if any, would be relevant.
- Whether laboratory findings translate to people at all.
What better evidence would look like
Larger, pre-registered trials using DNA-confirmed species and a fully characterised material, with triterpene and polysaccharide content reported, run independently and measuring outcomes that matter to people.
Our approach
We make our Reishi tincture from UK-grown fruiting bodies, extracted in both hot water and alcohol, and describe it by what it is and how it’s made, not by what it might do. For the wider picture, see The Complete Guide to Reishi.
References
- Gao YH, Lan J, Dai XH, Ye JX, Zhou SF. A phase I/II study of Ling Zhi mushroom Ganoderma lucidum extract in patients with type II diabetes mellitus. International Journal of Medicinal Mushrooms. 2004;6(1):33–39.
- Wang CW, Tschen JSM, Sheu WHH. Ganoderma lucidum on metabolic control in type 2 diabetes subjects: a double blinded placebo control study. Journal of Internal Medicine of Taiwan. 2008;19:54–60.
- Chu TTW, et al. Study of potential cardioprotective effects of Ganoderma lucidum (Lingzhi): results of a controlled human intervention trial. British Journal of Nutrition. 2012;107:1017–1027.
- Klupp NL, Kiat H, Bensoussan A, Steiner GZ, Chang DH. A double-blind, randomised, placebo-controlled trial of Ganoderma lucidum for the treatment of cardiovascular risk factors of metabolic syndrome. Scientific Reports. 2016;6:29540.
- Klupp NL, et al. Ganoderma lucidum mushroom for the treatment of cardiovascular risk factors. Cochrane Database of Systematic Reviews. 2015;(2):CD007259.
- Wanmuang H, et al. Fatal fulminant hepatitis associated with Ganoderma lucidum (Lingzhi) mushroom powder. Journal of the Medical Association of Thailand. 2007;90(1):179–181.
- LiverTox: Clinical and Research Information on Drug-Induced Liver Injury. Lingzhi (Reishi). National Institute of Diabetes and Digestive and Kidney Diseases.
Study titles are reproduced as published and are not claims made by Spore & Bloom.