Reishi: the mushroom of calm evenings

Reishi is the Japanese name for Ganoderma lucidum, a woody bracket fungus with a shiny, varnished cap that runs from deep red to chestnut brown. In China it is called lingzhi, sometimes written ling zhi or lin zi. British field guides know it as the lacquered bracket, and it does grow here on dead or dying hardwood such as oak, though you would be lucky to spot one.

It likes warm, humid conditions. Almost all the Reishi in supplements is cultivated, mostly in East Asia, on hardwood logs or sawdust rather than picked from the wild.

This is not a mushroom you cook. It is tough, corky and very bitter, so it has always been dried and then simmered into tea, ground into powder or, more recently, concentrated into an extract. The bitterness comes from compounds called triterpenes, one of the two groups of ingredients that researchers study most.

A small point on names. Genetic work has shown that much of the Reishi grown commercially in Asia is a close relative, now often called Ganoderma lingzhi or Ganoderma sichuanense. Most labels and studies still say Ganoderma lucidum, so this guide does too.

Few mushrooms have a longer written record. Reishi appears in the Shennong Bencao Jing, a Chinese herbal text put together around 2,000 years ago, where it sits in the top tier of substances considered suitable for taking over long periods. That standing is where the nickname the mushroom of immortality comes from.

Wild Reishi was scarce, so for centuries it was mostly kept for emperors and the wealthy. Its curling shape shows up in Chinese painting, carving and palace decoration as a sign of good fortune and long life. Reliable cultivation only arrived in the 1970s, when growers in Japan worked out how to farm it at scale, and that is why it went from rare to easy to buy.

In traditional Chinese practice Reishi was used as a calming, restorative tonic. It was taken for restlessness and poor sleep, and to keep up general vitality. Those are descriptions of traditional use rather than proven effects. Plenty of people in the UK now take it in the evening as part of winding down, which echoes that old habit.

Reishi contains hundreds of compounds, but research keeps coming back to two groups.

• Polysaccharides, especially beta-glucans. These are long chains of sugar molecules that dissolve in hot water. Most of the immune research on Reishi focuses on them.
• Triterpenes, including ganoderic acids. These give Reishi its bitter taste and dissolve better in alcohol than in water. Researchers have suggested they act on GABA signalling in the brain, a theory drawn largely from laboratory and animal work.

Reishi also contains sterols, proteins and small amounts of minerals.

Which part of the fungus you get matters. The fruiting body is the glossy cap you can see. The mycelium is the root-like network underneath, and when it is grown on grain the finished powder can contain a fair amount of starch from that grain. The spores are microscopic and have a hard shell, so they are usually cracked before use or pressed into spore oil. Most human trials have used fruiting body extracts or spore powder.

How it is extracted matters too. Hot water pulls out the polysaccharides. Alcohol pulls out more of the triterpenes. A dual extract uses both.

An extract ratio tells you how concentrated a product is. In Starshroooms, the Reishi is a 20:1 extract, which means 20kg of dried mushroom goes into every 1kg of extract. That makes Reishi the most concentrated ingredient in the gummy. A ratio says nothing about which compounds made it through, though, so some brands also quote a percentage of beta-glucans or triterpenes.

Sleep is the reason many people first look up Reishi, partly because of its traditional use for restlessness. The research is newer and thinner than you might expect.

Animal work. In a 2012 study by Cui and colleagues, rats given Reishi extract for three days slept longer in total and spent more time in non-REM sleep at the highest dose, 80mg per kg of body weight. REM sleep did not change. The effect seemed to be linked to a signalling molecule called TNF-alpha. Rat sleep is a long way from human sleep, so this points to a question worth asking rather than an answer.

Human work. At the SLEEP 2026 conference in June 2026, Dr Ching Xie presented an eight week trial in 218 adults with chronic insomnia, reported here. Half took 980mg of Reishi extract standardised to 6% triterpenes each night and half took 5mg of melatonin. Scores on the Insomnia Severity Index dropped in both groups, by an average of 8.7 points with Reishi and 5.6 points with melatonin. Of the 218 people who started, 209 finished, and no serious side effects were reported.

That trial is interesting, but it has limits:

• It was presented as a conference abstract and has not yet appeared as a full peer reviewed paper.
• There was no placebo group, so it compares two active options.
• It lasted eight weeks, which tells us nothing about longer use.

At the time of writing, no large placebo controlled human trial of Reishi for sleep has been published.

A handful of human studies have looked at tiredness and low mood, mostly in people who were already unwell.

In a 2005 trial by Tang and colleagues, 132 people in China diagnosed with neurasthenia took either a Reishi polysaccharide extract called Ganopoly (1,800mg three times a day) or a placebo for eight weeks. Neurasthenia is a diagnosis used in some countries for lasting fatigue, poor concentration and disturbed sleep. By the end, 51.6% of the Reishi group were rated as more than minimally better, compared with 24.6% on placebo. Fatigue scores fell by 28.3% with Reishi and 20.1% with placebo.

A 2020 pilot trial in Spain gave women with fibromyalgia 6g a day of finely milled Reishi or a placebo for six weeks. There were no statistically significant differences between the groups, although happiness and depression scores in the Reishi group moved in a positive direction from where they started.

Reviews of Reishi polysaccharides and tiredness after exercise lean mostly on animal studies. Whether any of this applies to healthy adults has not really been tested.

This is the most studied area, and also the one where claims most often run ahead of the evidence.

In test tubes and animals, Reishi beta-glucans interact with white blood cells, change the activity of genes involved in inflammation and raise the activity of natural killer cells, a type of white blood cell. That is the basis for Reishi's reputation, but lab results often fail to carry over to people.

Human data is limited:

• Wicks and colleagues, 2007: 16 healthy volunteers took 2g of Reishi extract or placebo twice a day for ten days. No side effects showed up. Natural killer cell counts rose during the study but the change was not statistically significant.

Changes in blood markers are not the same as catching fewer colds. No published trial has shown that healthy people who take Reishi get ill less often. For a vitamin that has an authorised claim here, look at vitamin C or zinc, which contribute to the normal function of the immune system.

Animal studies suggested Reishi might lower blood sugar and triglycerides and raise HDL, the so-called good cholesterol. Human trials have been far less clear.

• Wachtel-Galor and colleagues, 2004: in ten healthy volunteers, one 1.1g dose of Reishi raised the antioxidant capacity of their blood, peaking about 90 minutes later. After ten days at 0.72g a day, blood fats tended to fall, but not by a statistically significant amount. No harmful changes were seen.
• Chu and colleagues, 2012: 26 people with borderline high blood pressure or cholesterol took 1.44g of Reishi a day or a placebo for 12 weeks each, in turn. Blood pressure and weight did not change. Insulin levels and a measure of insulin resistance were lower on Reishi than placebo.
• Klupp and colleagues, 2016: 84 people with type 2 diabetes and metabolic syndrome took 3g a day of Reishi, with or without Cordyceps, or a placebo for 16 weeks. Reishi made no difference to HbA1c, fasting blood sugar or any of the secondary measures, which included blood pressure and cholesterol.

The Klupp trial was the largest and longest of the three, and it found nothing. Studies looking at antioxidant enzymes over four to 12 weeks have also found no lasting change.

If you have diabetes or high blood pressure and take medicine for it, speak to a pharmacist before trying Reishi. Some studies hint at small effects on blood sugar and blood pressure, and adding a supplement on top of treatment is worth a quick check.

Here is a plain summary of where things stand on 26 September 2026.

Where results have been encouraging

• Men's urinary symptoms. In a 2008 trial by Noguchi and colleagues, 88 Japanese men over 49 took 6mg of a Reishi alcohol extract or a placebo daily for 12 weeks. Their prostate symptom scores fell by 2.1 points, more than placebo. Urine flow, prostate size and PSA did not change.
• Short term changes in immune markers and blood antioxidant capacity.
• Sleep, in one unpublished comparison with melatonin.

Where results have been weak or negative

• Blood sugar, blood fats and blood pressure in people with type 2 diabetes.
• Fibromyalgia symptoms.
• Alzheimer's disease. A 2018 pilot trial of spore powder in 42 patients found no difference from placebo after six weeks.

What has barely been studied

• Healthy adults taking Reishi for months or years.
• Reishi in combination products, including gummies.
• Head to head comparisons of fruiting body, mycelium and spore products.

Most trials were small, many came from a single research group or used a single branded extract, and few ran longer than three months. You can browse every ingredient's studies on our research page.

Reishi comes in more forms than most mushrooms:

• Dried slices, simmered into a bitter tea
• Powder, stirred into drinks or smoothies
• Capsules and tablets
• Liquid tinctures
• Spore powder and spore oil
• Gummies and mushroom coffee blends

Dose. There is no agreed dose. Traditional amounts of dried whole mushroom run from about 1.5g to 9g a day. Extracts are stronger per gram, since a 10:1 extract packs the compounds from roughly 10g of dried mushroom into 1g, so the right amount depends entirely on the product. Trial doses have ranged from 6mg of a concentrated alcohol extract to 6g of milled mushroom a day. Follow the label and do not stack several Reishi products.

Timing. Nothing in the research says one time of day is better, but most people take Reishi in the evening because of its traditional calming use. If it upsets your stomach, taking it with food is worth trying.

How long. Most human studies ran for four to 16 weeks. If you try it, give it a month before deciding what you think.

How to choose a Reishi product

• Check the label names the part used: fruiting body, mycelium or spores.
• Look for an extract ratio or a standardised percentage of beta-glucans or triterpenes.
• Prefer brands that test for heavy metals and contaminants, since fungi absorb what they grow on.
• Buy from a seller with a UK address and a way to contact them.
• Walk away from anything that says it treats, cures or prevents an illness.

In short term trials Reishi has generally been well tolerated. Reported side effects include:

• Nausea, upset stomach, indigestion or diarrhoea
• Dry mouth or constipation
• Itchy skin or a rash
• Dizziness
• Trouble sleeping, in a small number of people

Liver. There are rare case reports of liver injury. A 2007 report from Thailand described a fatal case of hepatitis in someone who had switched from boiled Reishi to a powdered product for one to two months, alongside other medicines. Nobody can say for certain that Reishi caused it, but stop taking it and see a doctor if you notice yellow skin or eyes, dark urine or pain under your right ribs.

Long term safety has not been studied.

Check with your GP or pharmacist first if you:

• are pregnant or breastfeeding, as there is no safety data
• take blood thinners such as warfarin, clopidogrel or daily aspirin, or have a bleeding disorder, because Reishi may slow clotting
• have surgery planned, since the usual advice is to stop at least two weeks beforehand
• take immunosuppressants after a transplant or for an autoimmune condition
• have an autoimmune condition, including autoimmune skin conditions, which may flare
• take medicines for diabetes or blood pressure
• have liver or kidney disease
• take medicines broken down by the liver enzymes CYP1A2, CYP2E1 or CYP3A, which Reishi polysaccharides inhibited in lab tests

Reishi is not suitable for children unless a doctor advises it. You can report a suspected side effect from a herbal product to the MHRA through the Yellow Card scheme.

What UK labels can say. No health claim for Reishi has been authorised on the Great Britain register of nutrition and health claims, and claims for botanical ingredients have sat on an on hold list for years. No food supplement can say it prevents, treats or cures a disease. A careful UK brand will describe traditional use and research rather than promise results. If an advert says Reishi will fix your sleep or your immune system, treat that as a warning sign.

NHS guidance. The NHS has no specific advice on Reishi. Its general line on supplements applies: they do not replace a varied diet, and you should tell your GP or pharmacist about anything you take, especially before starting a new medicine.

Where to buy it. Reishi is sold in Holland & Barrett, independent health food shops and some pharmacies, and by many UK brands online, as capsules, powders, tinctures, teas and gummies. A few small UK growers produce Reishi too.

In Starshroooms. Starshroooms combine six mushrooms with Panax Ginseng in a vegan, caffeine free blackcurrant gummy. The Reishi is a 20:1 extract and sits alongside Chaga (10:1), Maitake (10:1), Lion's Mane (2:1), Cordyceps and Tremella. Each two gummy serving also contains pantothenic acid, which contributes to normal mental performance, and iodine, which contributes to normal cognitive function. Many customers take their two gummies 30 to 60 minutes before bed. The studies in this guide looked at Reishi on its own, often in other forms and amounts, and did not test our gummies.

If you want to read about the other ingredients, see our guides to Lion's Mane, Cordyceps, Chaga, Maitake, Tremella and Panax Ginseng, or browse all our mushroom gummies. For an evening routine without mushrooms, our ashwagandha guide covers a different ingredient.