Does reishi support the immune system? Reishi has more human immune research than most medicinal mushrooms, but read closely, it's mostly about blood test changes, not fewer infections. Trials in healthy adults, children, athletes and people with cancer have found shifts in immune cell counts and activity after reishi or its beta-glucans. No trial has shown that reishi prevents colds, flu or other infections. Here's what each human trial measured, what it found, and how to use reishi sensibly if you want to try it.
Reishi's human immune evidence is real but indirect. In a 12-week placebo-controlled trial in healthy adults, reishi beta-glucan raised T-cell and natural killer (NK) cell counts and NK cell activity (Chen 2023). A similar trial in children aged 3 to 5 found higher lymphocyte counts with beta-glucan-enriched yogurt (Henao 2018). A Cochrane review of five cancer trials found small increases in CD3, CD4 and CD8 cells, but rated the studies' quality as poor (Jin 2016). A 10-day safety trial in healthy adults found no significant immune change (Wicks 2007). None of these measured how often people got ill. Reishi changes immune markers; whether that means fewer infections is untested.
This article is for healthy adults curious about reishi. If you have an immune condition, cancer or an autoimmune disease, or take immune-suppressing medicine, talk to your doctor before using it.
What Is Reishi?
Reishi (Ganoderma lucidum), known as lingzhi in China, is a hard, glossy, reddish-brown bracket fungus that grows on hardwood trees. It's too tough and bitter to eat, so it's taken as a tea, powder, extract or tincture. It's one of the most traditional medicinal mushrooms in East Asia.
Its two main groups of active compounds are polysaccharides, especially beta-glucans, and bitter compounds called triterpenes. Beta-glucans are the ones linked to immune effects. Hot water extracts them well, while triterpenes need alcohol. Our guide on how to read a reishi label explains why this matters when you're comparing products.
How Might Reishi Affect the Immune System?
Beta-glucans are large sugar molecules found in the cell walls of fungi. Immune cells in the gut lining recognise them through specific receptors. In lab and animal studies, this recognition activates immune cells such as macrophages, NK cells and T cells, and changes the signalling molecules they release.
This is often called "immunomodulation" rather than "immune boosting". The effect isn't simply turning the immune system up. It's a set of shifts in different cell types and signals, and their real-world meaning depends on the person.
What Did Trials in Healthy People Find?
Healthy adults (Chen 2023). In a randomised, double-blind, placebo-controlled trial in Taiwan, healthy adults aged 18 to 55 took reishi beta-glucan or placebo daily for 84 days. Compared with placebo, the reishi group had higher counts of several T-cell types (CD3, CD4 and CD8), a better CD4 to CD8 ratio, more NK cells, higher NK cell activity and different immunoglobulin A levels. Liver and kidney tests didn't change (Chen 2023).
Young children (Henao 2018). In Colombia, children aged 3 to 5 ate yogurt with or without reishi beta-glucans daily for 12 weeks. The beta-glucan group had higher counts of total lymphocytes and several T-cell types. The yogurt was well tolerated, with no abnormal liver or kidney tests (Henao 2018). Don't give reishi supplements to children without medical advice, though; our article on mushroom supplements for children explains why.
Safety trial (Wicks 2007). In 16 healthy volunteers, 2 g of reishi extract twice a day for 10 days caused no adverse effects. NK cell markers rose during the study and returned to baseline afterwards, but the change wasn't statistically significant, and other immune cells didn't change (Wicks 2007). Ten days may be too short to see much.
Football players (Zhang 2008). Forty male football players took part in a 28-day altitude training programme. The hard training lowered a T-cell ratio that's often used as a marker of immune strain. The group taking the higher dose of reishi capsules showed a trend towards a smaller drop, but the difference wasn't statistically significant (Zhang 2008).
What About Trials in People With Cancer?
Most reishi immune research has been done in cancer patients, often in China, using a polysaccharide extract called Ganopoly.
In one study, 34 people with advanced cancer took 1,800 mg of Ganopoly three times a day for 12 weeks, and 30 were assessed. NK cell activity, some signalling molecules and NK cell numbers rose compared with their own starting levels (Gao 2003). There was no placebo group, so it's hard to know how much was due to reishi.
A similar open study in advanced lung cancer found no significant change in average immune markers, although some individual patients responded strongly (Gao 2005).
The Cochrane review pooled five randomised trials in cancer patients. Reishi taken alongside chemotherapy or radiotherapy was linked to small increases in CD3, CD4 and CD8 cells, and to better quality of life in four studies. But the reviewers rated the trials' methods as generally unsatisfactory, and found no evidence on long-term survival. They concluded that reishi isn't justified as a first-line cancer treatment (Jin 2016).
If you're being treated for cancer, don't take reishi without telling your oncology team. Our guide on reishi side effects and interactions explains why.
Is Reishi Safe for Immune Use?
It's generally well tolerated in trials of up to a few months. The most common side effects are dry mouth, stomach upset and, sometimes, skin rash. Some points to watch:
- Bleeding. Reishi may reduce platelet clumping. Take care with blood thinners, and stop it about two weeks before surgery.
- Liver. Rare cases of liver injury have been reported, including one after reishi powder combined with alcohol (Guedikian 2023). Stop if you notice yellow skin, dark urine or abdominal pain.
- Autoimmune conditions. Because reishi affects immune activity, its effect in autoimmune disease is uncertain. See our article on mushrooms and autoimmune conditions.
- Immunosuppressants. After an organ transplant or with immune-suppressing drugs, don't take reishi without medical advice.
- Pregnancy and breastfeeding. There's not enough safety data.
How Should You Take Reishi for Immune Support?
The positive trials used beta-glucan products taken daily for about 12 weeks. That suggests two practical points.
First, form matters. Beta-glucans dissolve in hot water, so look for a hot water or dual extract, or brew dried reishi as a tea. Raw powdered reishi releases fewer beta-glucans. Our comparison of reishi powder vs capsules vs tincture explains the trade-offs.
Second, consistency matters more than timing. The trials ran for months, not days. A single dose at the first sign of a cold has no evidence behind it. Our reishi dosage guide covers typical amounts, and our reishi capsules contain a dual extract made from the fruiting body.
Is Reishi the Best Mushroom for Immunity?
It depends what you mean by evidence. Turkey tail has stronger trial data in cancer care, but those trials used specific prescription extracts. Reishi has more trials in healthy people. Our comparison of turkey tail vs reishi for immune support weighs this up, and our guide to the best mushrooms for immunity covers other options.
No mushroom replaces vaccination, sleep, physical activity and a varied diet, which have far better evidence for preventing infections.
Frequently Asked Questions
Does reishi prevent colds and flu?
That hasn't been tested. Trials show reishi beta-glucans change immune cell counts and activity, but none has measured how often people catch colds or flu.
How long does reishi take to affect the immune system?
The positive trials ran for about 12 weeks. A 10-day trial found no significant change. If you try it, plan on taking it daily for at least two to three months.
Is reishi an immune booster?
It's better described as an immune modulator. It shifts several immune cell types and signals rather than simply turning immunity up, and the meaning of those shifts for health isn't fully known.
Can I take reishi with an autoimmune disease?
Ask your doctor first. Reishi affects immune activity, and there are no trials showing it's safe or helpful in autoimmune conditions.
Which form of reishi is best for immunity?
A hot water or dual extract, or reishi brewed as a tea, because the immune-active beta-glucans dissolve in hot water. The trials used beta-glucan-rich extracts.
Related Articles
- Turkey Tail vs Reishi for Immune Support
- Reishi Side Effects and Drug Interactions
- Reishi Dosage Guide
- How to Read a Reishi Label
- Reishi vs Chaga
Sources
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- Henao SLD, Urrego SA, Cano AM, Higuita EA. Randomized clinical trial for the evaluation of immune modulation by yogurt enriched with β-glucans from lingzhi or reishi medicinal mushroom, Ganoderma lucidum, in children from Medellin, Colombia. Int J Med Mushrooms. 2018;20(8):705-716. PubMed 30317947
- Wicks SM, Tong R, Wang CZ, et al. Safety and tolerability of Ganoderma lucidum in healthy subjects: a double-blind randomized placebo-controlled trial. Am J Chin Med. 2007;35(3):407-414. PubMed 17597499
- Zhang Y, Lin Z, Hu Y, Wang F. Effect of Ganoderma lucidum capsules on T lymphocyte subsets in football players on "living high-training low". Br J Sports Med. 2008;42(10):819-822. PubMed 18048435
- Gao Y, Zhou S, Jiang W, Huang M, Dai X. Effects of ganopoly (a Ganoderma lucidum polysaccharide extract) on the immune functions in advanced-stage cancer patients. Immunol Invest. 2003;32(3):201-215. PubMed 12916709
- Gao Y, Tang W, Dai X, et al. Effects of water-soluble Ganoderma lucidum polysaccharides on the immune functions of patients with advanced lung cancer. J Med Food. 2005;8(2):159-168. PubMed 16117607
- Jin X, Ruiz Beguerie J, Sze DM, Chan GC. Ganoderma lucidum (reishi mushroom) for cancer treatment. Cochrane Database Syst Rev. 2016;4:CD007731. PubMed 27045603
- Guedikian R, Kim B, Singh G, Alexander R. Ganoderma lingzhi (reishi mushroom)-induced acute liver injury in the setting of alcohol use: a case report and review of the literature. Cureus. 2023;15(9):e45953. PubMed 37885515