Reishi mushroom (Ganoderma lucidum) ranks among the most revered herbs in traditional Chinese medicine. For over two thousand years, practitioners have prescribed it for longevity, vitality, and what ancient texts describe as “nourishing the spirit.” The mushroom’s Chinese name, lingzhi, translates roughly to “divine mushroom” or “mushroom of immortality.”

But does modern science support these ancient claims? The short answer is: somewhat, but with important caveats. Most research on reishi consists of small trials, animal studies, or laboratory experiments. While some findings look promising, I wouldn’t bet the farm on reishi being a miracle cure for anything.

What Is Reishi Mushroom?

Reishi is a hard, woody fungus that grows on dead or dying hardwood trees, particularly oak, maple, and plum. Wild specimens are rare, which historically made them extraordinarily valuable. The Chinese emperors reportedly paid fortunes for specimens believed to grant immortality.

Modern cultivation techniques have made reishi widely available as a supplement. You’ll find it in capsules, powders, teas, and tinctures. The mushroom itself is too tough and bitter to eat directly, so processing is necessary.

The two main bioactive compounds in reishi are:

Polysaccharides (particularly β-glucans): These complex carbohydrates may modulate immune function. β-glucans from various sources have been studied for their effects on immune cells.
Triterpenes (ganoderic acids): These bitter compounds give reishi its characteristic taste and may have liver-protective, anti-inflammatory, and blood pressure-lowering properties.

How Is Reishi Mushroom Taken?

Since reishi isn’t approved for treating any medical condition, there’s no officially recommended dosage. The doses used in clinical trials vary widely, from around 1,000 mg to 5,400 mg daily.

Common preparation methods include:

Dried powder or capsules: The most convenient form. Typical doses range from 1.5 to 9 grams daily of dried mushroom equivalent.
Hot water extract: Traditional preparation involves simmering sliced reishi in hot water for hours. This extracts the water-soluble polysaccharides but leaves behind the triterpenes.
Alcohol (ethanol) extract: This pulls out the triterpenes that water cannot dissolve.
Dual extraction: Combines both methods to capture the full spectrum of compounds.

If you’re considering reishi supplements, quality matters enormously. The supplement industry is poorly regulated, and products vary wildly in their actual content. Look for products that specify the extraction method and have third-party testing.

What Does the Research Say? 9 Potential Benefits

Let me be clear upfront: most reishi research comes with significant limitations. Small sample sizes, short durations, and lack of standardised preparations make it difficult to draw firm conclusions. That said, here’s what the science shows so far.

1. May Support Liver Health

The liver handles an enormous workload: metabolising nutrients, producing bile, synthesising proteins, storing vitamins, and detoxifying harmful substances. Given this complexity, liver damage can cascade into serious health problems.

A 6-month randomised, double-blind, placebo-controlled crossover study followed 42 healthy middle-aged volunteers with mild liver dysfunction (elevated GOT, GPT, and fatty liver on ultrasound). Those taking reishi extract showed significantly increased total antioxidant capacity, plasma thiols, and glutathione levels compared to placebo 1.

More importantly, liver enzymes GOT and GPT decreased over time, and abdominal ultrasound showed some participants’ livers reverting from mild fatty liver to normal appearance.

My take: This is one of the more robust reishi studies, with a proper control group and reasonable duration. The antioxidant improvements were statistically significant. Still, 42 people isn’t a large sample, and we’d need bigger trials to confirm these findings. If you’re concerned about fatty liver, reishi might be worth discussing with your doctor, but don’t expect dramatic results.

2. May Modulate Immune Function in Athletes

Intense training stresses the immune system. Athletes often experience a temporary dip in immune function following heavy exercise, which is why many report catching colds after marathons or particularly gruelling training blocks.

A randomised controlled trial gave reishi extract to 40 male footballers undergoing high-altitude training (living high, training low protocol) for 28 days. Those taking reishi showed better maintenance of their CD4+/CD8+ ratio compared to controls 2.

The CD4+/CD8+ ratio is a marker of immune balance. When it drops too low, it can indicate immune suppression.

Worth noting: This study specifically looked at elite athletes under extreme physiological stress. Whether reishi would benefit sedentary individuals or recreational exercisers remains unclear. The mechanism might involve the β-glucan polysaccharides, which have documented effects on immune cell activity in laboratory studies.

3. Does Not Appear to Help Alzheimer’s Disease

I’m including this because it’s important to know what reishi doesn’t do, not just what it might do.

A preliminary randomised controlled trial gave reishi spore powder capsules to 42 Alzheimer’s patients for 6 weeks. Compared to placebo, there were no significant improvements in Alzheimer’s disease symptoms (measured by the Alzheimer’s Disease Assessment Scale), quality of life (WHO questionnaire), or neuropsychiatric symptoms 3.

The honest truth: If you’re hoping reishi might help a loved one with dementia, I’d look elsewhere. This trial was small and short, but the complete lack of any positive signal is discouraging. The ancient claims about reishi “nourishing the mind” don’t seem to translate to modern dementia treatment.

4. May Reduce Seizure Frequency in Epilepsy

A retrospective study followed 18 people with epilepsy who took reishi spore powder for 8 weeks. Compared to their pre-treatment baseline, participants experienced significantly fewer seizures per week 4.

However, the duration of individual seizures and quality of life measures didn’t significantly improve.

The catch: This wasn’t a controlled trial. Without a placebo group, we can’t separate the reishi effect from placebo effect, natural variation in seizure frequency, or other factors. Anyone with epilepsy should absolutely not adjust their medications based on this single, uncontrolled study.

5. May Support Cancer Treatment (as an Adjunct)

Cancer is an area where reishi has attracted considerable research interest, but the results require careful interpretation.

A Cochrane Review examined 5 randomised controlled trials involving 373 cancer patients and concluded there’s no clear evidence that reishi alone improves long-term survival or should be used as a first-line cancer treatment 5.

However, the same review noted that when reishi was added to conventional chemotherapy or radiotherapy, patients showed improved treatment response rates and better immune function markers. Some patients also reported improved quality of life.

In practice: Reishi is not a cancer treatment. Full stop. But for patients already receiving conventional treatment, adding reishi might help reduce some treatment side effects and support immune function. This should only be done with oncologist approval, as reishi could potentially interact with chemotherapy drugs.

6. Does Not Significantly Affect Cardiovascular Risk Factors

Given reishi’s reputation in traditional medicine, you might expect it to improve heart health markers. A Cochrane Review analysing 5 randomised controlled trials with 398 participants found otherwise 6.

Reishi did not produce significant effects on:

Glycated haemoglobin (HbA1c)
Total cholesterol
LDL cholesterol
Triglycerides
Body mass index
Fasting blood glucose
Blood pressure

My assessment: This is disappointing for those hoping reishi would be a cardiovascular tonic. If you’re managing heart disease risk factors, focus on proven interventions: diet, exercise, and medications as prescribed. Fish oil has stronger evidence for cardiovascular benefits.

7. May Improve Male Lower Urinary Tract Symptoms

Lower urinary tract symptoms affect a staggering proportion of men over 50, with some estimates suggesting up to 90% experience problems like frequent urination, weak stream, incomplete emptying, or nocturia. Common causes include benign prostatic hyperplasia, detrusor muscle dysfunction, and chronic prostatitis.

A randomised, double-blind controlled study gave reishi extract to 88 men with mild to moderate lower urinary tract symptoms for 12 weeks. Those taking reishi showed significant improvement in their International Prostate Symptom Score (IPSS) compared to placebo 7.

However, objective measures didn’t budge: maximum urine flow rate, mean flow rate, residual urine volume, prostate volume, serum PSA, and testosterone all remained unchanged.

Reality check: The symptom improvement is real and statistically significant, but the mechanism is puzzling. If the prostate isn’t changing, why do symptoms improve? Possibilities include placebo effect, anti-inflammatory actions affecting bladder tissue, or effects on neurological signalling. More research is needed to understand what’s happening here.

8. May Help Fibromyalgia Physical Function

Fibromyalgia is a chronic pain condition affecting 2-5% of the population, predominantly women. Beyond widespread pain, sufferers often experience fatigue, sleep disturbances, cognitive difficulties (“fibro fog”), and mood disorders.

A randomised, double-blind controlled study gave reishi to 64 women with fibromyalgia for 6 weeks. Those taking reishi showed improved performance on physical tests measuring aerobic endurance, lower extremity flexibility, and speed 8.

Worth considering: This is an interesting finding, though the study didn’t measure pain levels directly. The physical function improvements might relate to reishi’s potential effects on fatigue, inflammation, or sleep quality. Six weeks is a short trial, so we don’t know if benefits persist or increase over time.

9. May Extend Lifespan (Animal Evidence Only)

I’m including this because it’s the claim that gets the most attention, but I must be very clear: this is animal research only.

An animal study found that reishi significantly extended the lifespan of laboratory mice by up to 148 days, equivalent to roughly 16 human years if the comparison were valid 9.

What makes this study noteworthy is that researchers used what they considered a “reasonable” dose, equivalent to about 1,050 mg for a 75 kg adult human.

A word of caution: Animal studies frequently don’t replicate in humans. The biology of ageing differs between species, and mice have much shorter lifespans with different causes of death. I wouldn’t take reishi expecting it to add years to your life. The mechanisms involved (possibly reduced oxidative stress and improved immune surveillance) are interesting for researchers, but don’t translate into practical anti-ageing advice for humans yet.

What Are the Side Effects of Reishi?

Given its millennia of traditional use, reishi appears relatively safe for most people. However, human studies remain limited, so caution is warranted.

Reported side effects in the medical literature include:

Dry mouth
Itchy or dry throat
Gastrointestinal upset (nausea, bloating, diarrhoea)
Skin rashes
Nosebleeds
Bloody stools (rare but concerning)

The gastrointestinal symptoms are most common and usually mild. The bleeding-related side effects are less common but more serious, likely related to reishi’s effects on platelet aggregation.

If you experience any unusual bleeding while taking reishi, stop immediately and consult a doctor.

Who Should Avoid Reishi? 4 Contraindications

1. Pregnant or Breastfeeding Women

There’s simply no safety data for reishi during pregnancy or lactation. Given the unknowns, avoidance is the sensible choice. This isn’t because reishi is known to be harmful, but because we don’t know enough to say it’s safe.

2. People with Low Blood Pressure or Taking Antihypertensive Medications

Reishi may have blood pressure-lowering effects. For people already managing hypotension, or those taking blood pressure medications, this could be problematic.

Common antihypertensive medications include:

ACE inhibitors: captopril, enalapril, lisinopril
ARBs: losartan, valsartan, irbesartan
Calcium channel blockers: diltiazem, amlodipine, nifedipine
Diuretics: hydrochlorothiazide, furosemide

If you’re taking any of these, discuss reishi with your doctor before starting.

3. People with Bleeding Disorders or Taking Anticoagulant/Antiplatelet Medications

High-dose reishi may impair blood clotting. This is particularly concerning for those with existing bleeding disorders or those taking medications that affect clotting.

Medications to watch for include:

Aspirin
Clopidogrel (Plavix)
NSAIDs: diclofenac, ibuprofen, naproxen
Low molecular weight heparins: dalteparin, enoxaparin
Unfractionated heparin
Warfarin

If you take any blood thinners, avoid reishi or discuss carefully with your doctor.

4. People Undergoing Surgery

Because of the potential bleeding risk, stop taking reishi at least 2-3 weeks before any scheduled surgery. This includes dental surgery and other procedures that might involve bleeding. Resume only after your surgeon gives the all-clear.

Should You Take Reishi?

Based on the available evidence, reishi mushroom is not a treatment for any disease. The strongest evidence exists for modest improvements in immune function markers during physiological stress and mild improvements in urinary symptoms in men.

For most people, reishi is probably safe in standard supplement doses. But “probably safe” and “definitely helpful” are different things.

If you’re interested in reishi, consider:

Your specific goals: What do you hope to achieve?
The evidence: Is there actual research supporting reishi for your goal?
Quality: Can you find a reputable product with third-party testing?
Your health status: Do any contraindications apply to you?
Your doctor’s input: Supplements can interact with medications and conditions

For immune support, cordyceps, ashwagandha, and ginseng have comparable traditional reputations and varying levels of modern evidence. None are miracle supplements, but exploring your options makes sense.

The ancient Chinese may have been onto something with reishi, but the modern evidence remains preliminary. More rigorous research will eventually tell us whether the “mushroom of immortality” deserves its legendary status.

References

Chiu HF, et al. Triterpenoid- and polysaccharide-rich extracts from Ganoderma lucidum attenuate oxidative stress in middle-aged adults with mild fatty liver. J Food Drug Anal. 2018. PMC6130508
Chen YC, et al. Effect of Ganoderma lucidum on immune function in athletes during the LHTL training. Int J Sport Nutr Exerc Metab. 2007. PMID: 18048435
Wang GH, et al. Effect of Ganoderma lucidum spores on cognition and quality of life in patients with Alzheimer disease. Chin J Integr Med. 2018. PMID: 29742702
Wang M, et al. The therapeutic potential of Ganoderma lucidum spores in epilepsy. Seizure. 2018. PMID: 29879039
Jin X, et al. Ganoderma lucidum (Reishi mushroom) for cancer treatment. Cochrane Database Syst Rev. 2016. PMID: 27045603
Klupp NL, et al. Ganoderma lucidum mushroom for the treatment of cardiovascular risk factors. Cochrane Database Syst Rev. 2015. PMID: 25686270
Noguchi M, et al. Randomized clinical trial of an ethanol extract of Ganoderma lucidum in men with lower urinary tract symptoms. Asian J Androl. 2008. PMID: 18097505
Collado-Mateo D, et al. Effects of a Ganoderma lucidum-based supplementation on fibromyalgia. Nutr Hosp. 2015. PMID: 26545669
Chen SN, et al. Ganoderma lucidum extends lifespan in mice. FASEB J. 2011. Abstract