Reishi Benefits: What Studies Show, Side Effects and Who Should Avoid It

3 min read By Mataye

In brief

Reishi is linked to sleep, stress and immunity, but the human evidence is small and mixed. What the studies found, side effects and who should avoid reishi.

Reishi Benefits: What Studies Show, Side Effects and Who Should Avoid It

Reishi (Ganoderma lucidum) is used in traditional Chinese medicine for rest and general wellbeing, and today it is sold for sleep, stress and immune support. Human studies are small and mixed: a few report modest effects on urinary symptoms in men, blood fats, blood sugar and anxiety, while well-run trials on heart risk factors and fibromyalgia found no benefit. Here is the evidence claim by claim, and the safety points, which matter more with reishi than with most mushrooms. For what reishi is and how it tastes, see our reishi mushroom guide.

Evidence by claim

Claim What studies found Strength in people
Sleep and relaxation Traditional use, animal studies Little direct evidence
Stress and anxiety Small clinical study reported lower anxiety Limited
Immune support Lab, animal and small human studies Limited, mostly in people with cancer
Urinary symptoms in men Clinical studies reported improvement Limited
Blood sugar and blood fats Mild effects in some studies Mixed; trials in type 2 diabetes did not support reducing heart risk factors
Fibromyalgia Randomised trial No effect found
Alzheimer's disease Pilot study of spore powder Not helpful

Summary based on Memorial Sloan Kettering Cancer Center's review of the clinical studies.

Reishi for sleep

Reishi is often sold as an evening mushroom. The idea comes from traditional use and animal studies; good trials in people are lacking. Interestingly, insomnia is listed as a possible side effect. If you want reishi for sleep, choose a caffeine-free reishi tea, not a mushroom coffee.

Reishi and the immune system

Reishi contains beta-glucans and triterpenes that affect immune cells in the lab. A Cochrane review of reishi in people having cancer treatment found only small trials, all in China and of uneven quality. In them, adding reishi extract was linked with a better response to chemotherapy or radiotherapy and a better quality of life. On its own, it did not shrink tumours. That is not evidence for healthy people taking reishi to "boost immunity", and reishi is not a cancer treatment.

Reishi side effects

  • Nausea and insomnia (Memorial Sloan Kettering).
  • Liver injury has been reported, mostly with concentrated powders. If you have a liver condition, avoid it unless your doctor agrees.

Who should avoid reishi

  • People on blood thinners such as warfarin, or before surgery: reishi can increase the risk of bleeding.
  • People on immunosuppressants: reishi can enhance immune response.
  • People taking medicine for blood pressure or diabetes: it may add to their effect.
  • Pregnant or breastfeeding women: not enough safety data.
  • Anyone allergic to mushrooms.

How to take reishi

  • Tea: simmer dried slices for 30 minutes or more. Bitter.
  • Capsules or powder: check the dose and whether it is fruiting body, extract or spore powder.
  • In coffee: the bitterness disappears. Mataye Mushroom Coffee has 700 mg of reishi fruiting body per cup, with lion's mane, cordyceps, chaga and shiitake. Read our mushroom coffee guide or compare with lion's mane benefits.

Reishi, blood sugar and cholesterol

A Cochrane review of 5 trials (398 people, 1.4 to 3 g a day for 12 to 16 weeks) found no significant effect on HbA1c, total cholesterol or LDL (Klupp et al., 2015). A 16-week trial in 84 people with type 2 diabetes and metabolic syndrome, at 3 g a day with or without cordyceps, found no effect either (Klupp et al., 2016). See also mushroom coffee side effects.

Read next: ganoderma coffee compared.

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