Reishi

This is the claim Health Canada permits, and it's also the one with the most real laboratory support - so it's worth separating what has been measured in a test tube from what has been measured in a person.

In the lab, the picture is consistent. Reishi's beta-glucan polysaccharides activate immune cells - macrophages, T lymphocytes, natural killer cells - and set off the ordinary signalling cascade those cells use. Memorial Sloan Kettering's clinical summary describes the mechanism in some detail: reishi induces natural killer cell activity against cancer cell lines by switching on receptors called NKG2D and NCR, and its polysaccharides increase the display of MHC class I molecules on tumour cells. That is genuine, replicated cell biology. It is not, however, a demonstration that anything useful happens in a healthy person who drinks reishi tea.

In people, the studies are smaller and shorter. The clearest human work comes from Hong Kong, where researchers gave healthy volunteers reishi and measured what happened in their blood. In a controlled supplementation study published in the British Journal of Nutrition, plasma antioxidant capacity rose measurably after taking reishi - both after a single dose and after ten days of daily use - with no change in markers of liver or kidney stress. That is a real, measured, human effect, and it is the direct basis for the permitted 'source of antioxidants' wording. It is also a modest one: a shift in a blood measurement, not a change in how often anyone got sick.

On the immune side specifically, the best human data comes from an unusual place - the Cochrane review of reishi in cancer patients. Pooling five randomised trials, the reviewers found that reishi increased the percentages of CD3, CD4 and CD8 lymphocytes. So immune markers do move in people, not just in dishes. What nobody has done is the study most buyers actually care about: a large trial in healthy adults measuring whether reishi means fewer colds, fewer sick days, or faster recovery. Until that exists, 'supports the immune system' is a traditional-use claim with plausible mechanism behind it, not a proven outcome.

This is reishi's strongest human evidence, and it's also the claim Health Canada actually permits - reishi is approved as 'an adaptogen to help increase energy and resistance to stress over time.' Here's the study behind that idea.

In 2005, researchers in China ran a randomised, double-blind, placebo-controlled trial in 132 people diagnosed with neurasthenia - a formal diagnosis in the international classification of diseases, describing persistent fatigue, weakness and poor recovery after effort. Half received a standardised reishi polysaccharide extract, 1,800 mg three times a day; half received identical placebo. Neither the patients nor the researchers knew who got which. After eight weeks, 123 people were still assessable. On the clinicians' global severity rating, the reishi group improved by 15.5 per cent from baseline versus 4.9 per cent on placebo. On the participants' own sense of fatigue, reishi improved 28.3 per cent versus 20.1 per cent on placebo. Sense of well-being rose 38.7 per cent versus 29.7 per cent.

Read those numbers carefully, because they tell an honest story. Reishi beat placebo - but placebo did quite a lot on its own, and the gap between them on fatigue was under nine percentage points. That's a real effect, and a modest one.

A second, smaller trial points the same direction in a different group. A 2012 pilot study randomised 48 women with breast cancer who were on endocrine therapy and struggling with cancer-related fatigue, giving one group reishi spore powder for four weeks. Using standard fatigue and quality-of-life questionnaires, the reishi group reported less fatigue, better physical well-being, and less anxiety and depression than controls, with no serious side effects. But 48 people, four weeks, and a single centre is a pilot - the authors said so themselves.

The honest limitation across both: these were people who started out unwell and fatigued. Nobody has shown that reishi does anything measurable for the tiredness of an otherwise healthy person with a busy week.

This is the most common reason people buy reishi, and it has the weakest evidence on this page. We'd rather say that clearly than let it slide.

The tradition is genuine and very old. In Chinese medicine reishi is Ling Zhi, and its classical use is to nourish the Heart and calm the shen - the spirit or consciousness. Health Canada's monograph reflects this: it permits the TCM sentence about nourishing the Heart and strengthening qi and blood 'to treat Heart and Spleen deficiencies that manifest in insomnia, forgetfulness, fatigue, listlessness and poor appetite.' That is the only place the word insomnia appears, and it's inside a traditional-pattern description - it is not permission to say reishi helps you sleep. In practice, this has always been an evening ingredient: a bitter, woody decoction taken before bed.

The modern evidence is thinner than the tradition suggests. Sleep has usually been measured as a side note rather than a main outcome - in the neurasthenia trial, sense of fatigue and well-being improved, and in the breast cancer pilot the insomnia item on a quality-of-life questionnaire moved more in the reishi group than in controls. Both are secondary findings in small studies, in people with a specific condition. The animal work is more direct - mice given reishi extracts fall asleep faster and sleep longer, with the effect apparently running through the gut microbiome and serotonin - but mice are not a reason to make a human claim.

There is one newer piece of evidence people will encounter. In 2026, a trial of 218 adults with chronic insomnia comparing a reishi extract standardised to 6 per cent triterpenes against melatonin was presented as a late-breaking abstract at the SLEEP conference, reporting a larger drop in insomnia severity scores with reishi. We're flagging it because it's the biggest sleep study reishi has ever had - but a conference abstract is not a peer-reviewed paper, we cannot read its full methods, and it changes nothing about what's permitted in Canada. If it survives peer review, we'll upgrade this grade. Until then, sleep remains a traditional use.

One more honest wrinkle: insomnia is also listed among reishi's reported side effects. A minority of people find it does the opposite of what they expected.

Reishi is permitted in Canada as 'a liver tonic,' and that phrasing is doing careful work. It is a herbal-medicine use claim, resting on a long tradition and on textbook references, not on a modern trial showing improved liver function in people.

What exists is preclinical. In mice, reishi extracts have shown hepatoprotective effects - reducing liver damage from toxins such as cadmium, and protecting liver and kidney tissue under chemical stress. The triterpene fraction is generally credited with this. That's a plausible, reproducible animal finding, and it's the scientific basis people point to. What does not exist is a randomised human trial in which people with liver disease took reishi and their liver measurements improved. Memorial Sloan Kettering's clinical summary lists hepatoprotective activity explicitly as an in vitro and in vivo finding - lab and animal - and does not list a human liver outcome.

There is a genuinely uncomfortable counterweight here, and it belongs in this section rather than buried in the safety notes. Reishi has been linked to liver injury in a small number of published case reports. A 2004 report from Hong Kong described hepatotoxicity from a reishi formulation. In 2007, Thai clinicians reported a fatal case of fulminant hepatitis in a patient taking lingzhi mushroom powder. In both cases the patients had taken traditionally boiled lingzhi for a long time with no trouble, and became ill within one to two months of switching to a powdered preparation. A 2023 case report described acute liver injury in a person using reishi alongside alcohol.

Set that against the scale of use - reishi is consumed by millions of people worldwide - and these remain rare events. But they are the reason we treat the liver tonic claim as tradition rather than proof, and the reason we'd tell anyone with existing liver disease, or who drinks heavily, to speak to their doctor before starting.

We are including this because it is the single most-searched question about reishi, and because a serious, independent body has actually looked at it. Nothing here is a claim we make about our product - reishi is a food supplement, no cancer claim is permitted in Canada, and nothing on this page should be read as suggesting reishi treats, prevents or cures any disease. What follows is simply what the research found.

The Cochrane Collaboration - the international group that produces the most rigorous evidence reviews in medicine - published a review of Ganoderma lucidum for cancer treatment, updated in 2016. The reviewers found five randomised controlled trials with 373 participants in total: three in people with advanced lung cancer, one in people who had surgery for rectal cancer, and one in people with a mix of cancers. Pooling them, patients who had reishi extract added to their chemotherapy or radiotherapy were about 1.27 times more likely to respond to that treatment than those who did not. Immune markers - CD3, CD4 and CD8 lymphocyte percentages - increased, and quality of life after treatment was relatively better in the reishi groups. Reishi used on its own showed no significant effect on tumour shrinkage.

And now the part that matters most. Cochrane graded that evidence as low to very low quality. In their own words, it was unclear whether some of the studies had properly randomised participants at all, and very few people contributed data to each outcome. Cochrane's conclusion was not 'reishi works'; it was that the present evidence is insufficient to justify using reishi as a first-line cancer treatment, and that it could be considered as an alternative adjunct only alongside conventional treatment, with more well-designed trials needed. A 2023 systematic review of medicinal mushroom supplements in cancer reached a similar verdict: further research is needed to determine safety and effectiveness.

There are also practical hazards in this setting that get too little airtime. Reishi may interact with immunosuppressant drugs and, in theory, with chemotherapy agents that work through free radicals. Reishi spore powder has been shown to elevate the tumour marker CA72-4, which can confuse monitoring. If you are in treatment, this is a discussion for your oncology team - not a decision to make from a supplement page.

You will find reishi marketed for cholesterol, blood pressure and blood sugar. This one has actually been tested properly, and it didn't hold up. We think that deserves a section of its own, because negative results almost never get one.

In 2015, Cochrane published a review specifically on Ganoderma lucidum for cardiovascular risk factors. The reviewers pooled five randomised placebo-controlled trials covering 398 people, all of whom had type 2 diabetes, using doses of roughly 1.4 to 3 grams a day for 12 to 16 weeks. Across the primary outcomes - HbA1c (a three-month average of blood sugar), fasting plasma glucose, blood pressure, triglycerides and the cholesterol profile - there was evidence of no effect. The reviewers also judged the overall quality of the studies to be poor, and noted there was inadequate evidence to determine whether reishi is even safe in this population. Their conclusion was blunt: the existing randomised evidence does not support using reishi for cardiovascular risk factors.

A later trial reinforced it. In 2016, the same lead researcher ran a double-blind, randomised, placebo-controlled trial of reishi in people with metabolic syndrome, published in Scientific Reports - and again found no meaningful benefit for the cardiovascular risk factors measured. A separate study in women with fibromyalgia found reishi did not influence blood or body-composition measurements either.

The honest limitation cuts both ways: all of this work was done in people who already had metabolic disease, at moderate doses, over a few months. It is conceivable that reishi behaves differently in different people over longer periods. But that is speculation, and the evidence we actually have points to no effect. Health Canada permits no cholesterol, blood pressure or blood sugar claim for reishi - and on this evidence, it shouldn't.