Reishi Mushrooms: Health Benefits And Safety Considerations

Reishi mushrooms - discover the health benefits, safety considerations and ways to supplement with this fantastic fungus.

Reishi Mushrooms: Health Benefits And Safety Considerations photo

The Reishi or Lingzhi mushroom, botanical name Ganoderma lucidum, grows in hot and humid, subtropical environments such as China and Japan.1 Reishi mushrooms have a glossy appearance and the caps are a kidney or fan shaped. They are usually a reddish-orange-brown colour, however other mushrooms within the Ganoderma fungi family can be yellow, black and purple.

Knowledge of the medicinal value of the Reishi mushroom has been documented in ancient scripts and it has been recognised for its potential benefits to health and longevity for over two thousand years in Asia.1 Referred to as ‘the mushroom of immortality’, the Reishi or Lingzhi mushroom has traditionally been eaten to increase energy, improve heart health, enhance memory, ease the mind, soothe a cough and asthma, and to delay the effects of ageing.1,2 It is also believed to support the immune system and to reduce the risk of heart disease and cancer.3 However, these claims are typically based on traditional medicine and anecdotal evidence – more studies are required to determine scientifically the effects of the Reishi mushroom on health and wellbeing.

Whilst Reishi mushrooms are primarily consumed for their medicinal properties, nutritionally they also contain minerals such as phosphorus, calcium, sulphur, silica, potassium, selenium and magnesium, which are essential for human health. They also contain protein, and prebiotic fibre to help feed beneficial bacteria in our gut.1

Interest in medicinal mushrooms such as Reishi has grown in recent years and many Reishi dietary supplements are now available on the market in the form of teas, tinctures, powders and capsules. These supplements claim to support a wide range of issues from immune health, stress, liver protection, blood sugar balance, anti-ageing, neurological health, cognition and memory.

Scientific studies have identified numerous bioactive compounds in Reishi mushrooms that include peptidoglycans, triterpenes and polysaccharides such as Beta-Glucans. Researchers have found these compounds to have potential cholesterol-lowering, antioxidant, anti-inflammatory, anti-tumour and immune-stimulating properties, and they may also help to manage blood sugar levels.1 However, a lot of the research has been done on animals or in laboratory cell cultures, therefore more good quality human studies are required to test the effects of Reishi supplementation on human health.

To help you make an informed decision whether to take a Reishi supplement, we discuss some of the health conditions that Reishi might support, along with some tips on how to choose a Reishi supplement and potential safety issues to consider.

Health conditions that Reishi mushroom supplements might support:

Inflammatory conditions

Bioactive compounds, such as GAC1, have been extracted from the Reishi mushroom and studied for their potential to help with inflammatory conditions such as Crohn’s disease and asthma. One study found that the compound GAC1 was able to significantly reduce the production of a key inflammatory molecule associated with Crohn’s disease and asthma.4 Whilst this study revealed positive results, it looked at inflamed human tissues in a cell culture rather than the effects of GAC1 taken internally by individuals as a supplement, so further clinical studies are required.

Anti-ageing

A number of studies have identified antioxidant activity in the bioactive compounds of the Reishi mushroom. This means that these substances have the potential to scavenge for and neutralise unstable molecules in the body called ‘free radicals’, which can cause damage to cells and accelerate the ageing process.

Free radicals are formed from normal biological processes, such as energy production in cells, and also from UV light, smoking, environmental pollutants, stress and inflammation. The body has its own mechanisms for managing free radical production, including producing antioxidants such as glutathione that help to neutralise excess free radicals. However, when there is an imbalance between free radicals and the body’s ability to keep up with their removal, this can cause problems such as accelerated ageing and an increased risk of chronic disease.

One study found that Reishi polysaccharides (complex sugar compounds) have antioxidant activity and can potentially inhibit the production of harmful free radicals in human tissues following UV light exposure (5). Conversely, a trial involving 18 individuals found no significant effect on antioxidant status following Reishi supplementation, however this was a small study that was relatively short.3 It is clear that the evidence is still mixed and larger, more robust human studies are required to look at the long-term effects of Reishi mushroom supplements on the ageing process.

High blood pressure

A number of studies indicate that Reishi may help to reduce high blood pressure by controlling an enzyme involved in blood pressure regulation.6 However, some of these experiments were conducted on animals, and the outcomes of human experiments using Reishi supplements as an intervention for high blood pressure are mixed, with a significant benefit being found in some studies and no benefit found in others.6-9

Diabetes

Bioactive compounds from the Reishi mushroom may help to balance blood sugar levels and lower insulin resistance, which is a key issue in people with pre-diabetes and type 2 diabetes. One study in humans found a significant reduction in HbA1c (a measure of average blood sugar levels over the past 3 months) when participants were given Reishi mushroom capsules for 12 weeks following a Reishi mushroom supplement.10 Reishi supplements should not be used as a replacement for prescribed diabetic medications, however studies show the potential for Reishi mushroom compounds to help with managing blood sugar levels, which could be beneficial for individuals looking to reduce their risk of developing type 2 diabetes.11

Immune support

One of the more well-known properties of medicinal mushrooms is that they appear to have immune-stimulating activity.1 In the case of Reishi mushrooms, studies have found that they may enhance the immune system through increasing levels of white blood cells, which play a key role in fighting infection. Reishi mushrooms may also help to reduce inflammation and potentially inhibit tumour growth. This could be beneficial for people with suppressed immune systems as a result of chronic stress, overworking, poor diet or insomnia. However, due to the immune-stimulating effects of Reishi, caution should be taken if you have an autoimmune disorder and you take immunosuppressant medications, as this could interfere with the treatment and make symptoms worse.

Other studies have identified potential cholesterol-lowering and cognitive-boosting properties of Reishi mushroom compounds, and even the possibility for them to help with neurological health, anxiety and depression. However, most studies have been on animals and there have not been enough studies yet to support this effect in humans.

3 top tips for choosing a Reishi supplement

Reishi dietary supplements can be purchased as tinctures, capsules, powders or teas. With so many different products available, it can be hard to know where to start. If you are looking to buy a Reishi supplement, consider the following options:

  1. Teas are usually less potent and offer a gentler way to try a medicinal mushroom or herbal product to see if your body tolerates it. However, some of the bioactive compounds in the Reishi mushroom may not be water soluble, which could affect its effectiveness.
  2. Tinctures usually contain higher amounts of the active ingredient and are made using alcohol, which helps to extract the bioactive compounds more effectively.
  3. Powders and capsules are also stronger than teas and can be added to smoothies, juices or hot water as per the manufacturer’s instructions. Powders and capsules usually contain more parts of the mushroom, which are ground up and dried.

Choose a trusted supplement manufacturer – do a little research into the company to find out how they create their Reishi mushroom supplement. Some companies will only use the fruiting body of the mushroom since it is more nutrient-rich than the root. Take a look at the product’s ingredient list too. Are there lots of filler and preservative ingredients or is it a relatively pure product consisting of minimal, good-quality ingredients?

Are Reishi mushroom supplements safe to take?

Reishi mushroom supplements appear to be relatively safe to take provided they are created by reputable companies and are sourced from good-quality ingredients without contamination. However, if you have a pre-existing health condition, take medications, or are pregnant or breastfeeding, then it is advisable to speak to your GP to make sure it is safe for you.

The risk for potential interactions with medications should not be underestimated. For example, Reishi supplements can interact with blood-thinning drugs and with medications prescribed for high blood pressure and diabetes. Other herbal medicines and nutritional supplements that can lower blood pressure and blood glucose or those with potential blood-thinning effects (such as garlic) could also interact with Reishi supplements.12

One study highlighted a case of liver injury in two individuals following the consumption of a Reishi mushroom powder for 1-2 months, however this has not been reported in other studies involving more people.3,13

If you are due to have surgery, do not take Reishi supplements for at least two weeks before your surgery.

Summary

In conclusion, the Reishi mushroom is a complex fungus that may support general wellbeing and help in a range of health conditions. Preliminary research suggests that it may be effective for reducing inflammation, supporting cell health, boosting immune function, reducing high blood pressure, and helping to regulate blood sugar levels to reduce the risk of type 2 diabetes. There are many products available such as tinctures, teas, powders and capsules and it can be a good idea to choose a supplement that is made from the fruiting body of the mushroom, since this usually contains more nutrients and bioactive compounds. Reishi mushroom supplements still require more research into their effectiveness and safety, however overall studies indicate they are possibly safe, providing the above safety considerations are taken into account. A good rule of thumb is to avoid taking highly concentrated Reishi supplements long-term, and to follow the dosage recommendations on the individual product.

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  1. Wachtel-Galor S, et al. Herbal Medicine: Biomolecular and Clinical Aspects. 2nd edition. Boca Raton: CRC Press/Taylor & Francis, 2011.
  2. Lloyd A, et al. Identifying the “Mushroom of Immortality”: Assessing the Ganoderma Species Composition in Commercial Reishi Products. Front. Microbiol. [internet] 2018 July. Available from: https://www.frontiersin.org/articles/10.3389/fmicb.2018.01557/full#B51
  3. Wachtel-Galor S, Tomlinson B, Benzie IFF. Ganoderma lucidum (‘Lingzhi’), a Chinese medicinal mushroom: biomarker responses in a controlled human supplementation study. Br. J. Nutr. 2004; 91: 263-269.
  4. Liu C, Dunkin D, Lai J. Anti-inflammatory Effects of Ganoderma Lucidum Triterpenoid in Human Crohn’s Disease Associated with Down-Regulation of NF-κB Signaling. Inflamm Bowel Dis. 2016; 21(8): 1918-1925.
  5. Sheikha AFE. Nutritional Profile and Health Benefits of Ganoderma lucidum "Lingzhi, Reishi, or Mannentake" as Functional Foods: Current Scenario and Future Perspectives. Foods. [internet] 2022 April. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8998036/
  6. Gao YH, et al. A Phase I/II Study of Ling Zhi Mushroom Ganoderma lucidum (W.Curt.:Fr.) Lloyd (Aphyllophoromycetideae) Extract in Patients with Coronary Heart Disease. Int. J. Med. Mushrooms. 2018; 6(4): 327-334.
  7. Rizal, A, et al. Ganoderma lucidum Polysaccharide Peptide Reduce Inflammation and Oxidative Stress in Patient with Atrial Fibrillation. The Indonesian Biomedical Journal. 2020; 12(4): 384-389
  8. Chan SW, et al. The beneficial effects of Ganoderma lucidum on cardiovascular and metabolic disease risk. Pharm Biol. [internet] 2021 Dec. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8409941/
  9. Klupp NL, et al. A double-blind, randomised, placebo-controlled trial of Ganoderma lucidum for the treatment of cardiovascular risk factors of metabolic syndrome. Sci Rep. [internet] 2016 Aug. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4980683/
  10. Gao Y, et al. A phase I/II study of ling zhi mushroom ganoderma lucidum (w.curt.: fr.)Lloyd (aphyllophoromycetideae) extract in patients with type ii diabetes mellitus. Int. J. Med. Mushrooms. 2004; 6(1): 33-39.
  11. Wińska K, et al. Mushrooms of the Genus Ganoderma Used to Treat Diabetes and Insulin Resistance. Molecules. [internet] 2019 Nov. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6891282/
  12. Therapeutic Research Center - Natural Medicines Database. Reishi Mushroom, https://naturalmedicines.therapeuticresearch.com/databases/food,-herbs-supplements/professional.aspx?productid=905
  13. Wanmuang H, et al. Fatal fulminant hepatitis associated with Ganoderma lucidum (Lingzhi) mushroom powder. J Med Assoc Thai. 2007; 90(1): 179-181.