What are functional mushrooms?

Functional mushrooms are fungi people take for reasons beyond ordinary nutrition, and in Great Britain they're sold as food supplements rather than medicines. Lion's mane, reishi, chaga, cordyceps, shiitake and maitake are the ones you'll meet most often on a UK shelf. Only health claims listed on the Great Britain Nutrition and Health Claims register may legally be made about any of them, and most mushroom claims aren't on that list (GOV.UK, register last updated 19 May 2026).

I run a mushroom gummy company, so you'd expect me to tell you these things are remarkable. What I'd rather do is explain what the term covers, what the research has actually tested, and why UK products describe themselves so cautiously.

Key takeaways

•    No UK law defines the phrase "functional mushroom." It's an industry term. What the law does define is the line between a food supplement and a medicine: under MHRA Guidance Note 8, a product presented as preventing or treating disease is likely to be regulated as a medicine whatever its ingredients.

•    Only claims on the GB Nutrition and Health Claims register may be used in Great Britain. Botanical and fungal claims still under review when the UK left the EU were carried over unresolved, and any claim the European Commission hadn't decided by 1 January 2021 needs a fresh GB application (GOV.UK).

•    Most functional mushroom research sits at preliminary evidence or traditional use, not strong evidence. A 2025 GRADE-assessed review in Food Science & Nutrition pooled 17 randomised trials of reishi in 971 people and rated the certainty of the evidence very low across every outcome it examined.

•    The most-cited lion's mane trial involved 30 people. Mori and colleagues (Phytotherapy Research, 2009) randomised 30 Japanese adults aged 50 to 80 into two groups of 15 for 16 weeks. Preliminary evidence, and a very small sample.

•    A UK trial in healthy adults found mostly nothing. Docherty and colleagues at Northumbria University (Nutrients, 2023) gave 1.8 g of lion's mane daily to 41 healthy adults aged 18 to 45. One cognitive test out of several showed a faster result after a single dose. Most measures didn't move.

•    Species matters legally, not just biologically. A 2026 narrative review in Nutrients notes that Cordyceps militaris is listed as an unauthorised novel food in the EU catalogue, while Ophiocordyceps sinensis was confirmed as not novel for food supplement use (NutraIngredients, August 2025).

 

Contents

1.   What does "functional mushroom" actually mean?

2.   The species you'll see most often in UK products

3.   Functional mushrooms and magic mushrooms are separate things

4.   How Great Britain regulates functional mushrooms

5.   How strong is the evidence, really?

6.   What we make at DoctorShrooms, and what we don't claim

7.   Questions parents ask us

 

1. What does "functional mushroom" actually mean?

It means a mushroom taken for something other than calories, protein or flavour. That's the whole definition, and it's an industry one. No GB regulation uses the phrase.

Which is worth knowing before you shop, because a term with no legal meaning can't tell you anything about quality, dose or form. It only tells you why someone is selling it to you.

Some of these species are ordinary food. Shiitake and maitake turn up in supermarkets and restaurants. Others, like reishi and chaga, are woody and bitter, and almost nobody eats them as food. The category groups them by intention rather than by botany.

The line that does carry legal weight is the one between food and medicine. MHRA Guidance Note 8 sets out two tests: whether a product is presented as having properties for preventing or treating disease, and whether it's given with the intention of restoring or modifying physiological function by pharmacological, immunological or metabolic action. Fail either and you're selling an unlicensed medicine, no matter what's in the jar.

2. The species you'll see most often in UK products

Six species account for most of what's on sale in Britain. Here's what each one is, and what kind of evidence sits behind it.

Mushroom	Latin name	What it is	Strongest evidence level
Lion's mane	Hericium erinaceus	Edible, shaggy white, mild taste	Preliminary. Small human trials on cognition and mood exist (Mori 2009; Docherty 2023)
Reishi	Ganoderma lucidum	Woody bracket fungus, very bitter, not eaten as food	Preliminary at best. 17 randomised trials pooled in 2025 rated very low certainty
Cordyceps	Cordyceps militaris / Ophiocordyceps sinensis	Two distinct species often sold under one name	Preliminary and inconsistent (Jędrejko 2026)
Chaga	Inonotus obliquus	Birch-growing fungus, traditionally brewed as tea	Traditional use. Frequently cited antioxidant assay data is a weak proxy for anything you'd feel
Shiitake	Lentinula edodes	Common culinary mushroom, long food history worldwide	Traditional use, plus a long history as ordinary food
Maitake	Grifola frondosa	Culinary mushroom, sold fresh in the UK	Traditional use, with early research on its beta-glucan fractions

 

Two things to notice.

First, the evidence column says "preliminary" or "traditional use" the whole way down. Nothing in this category has the kind of repeated, large, human trial evidence you'd expect behind a licensed medicine.

Second, the cordyceps row has two Latin names in it. That's not tidiness on my part. In the supplement trade, material sold as Cordyceps sinensis is often a cultivated strain rather than the wild high-altitude fungus the name refers to, and the two species have different research behind them and different legal status. If a label just says "cordyceps," you can't tell which you've got.

3. Functional mushrooms and magic mushrooms are separate things

They are not the same, and this question comes up often enough that it deserves a plain answer.

The species in functional mushroom supplements are culinary and non-psychoactive fungi. They contain no psilocybin. They won't alter your perception, and they're sold in Britain as food supplements. Psilocybin is a controlled substance in the UK and has nothing to do with what's in a lion's mane capsule or a reishi tea.

That's the whole distinction. If you've been nervous about giving a mushroom supplement to a child because of the association, this is the bit that should settle it.

4. How Great Britain regulates functional mushrooms

Two separate systems apply, and brands trip over both.

Novel foods. Under assimilated Regulation (EU) 2015/2283, a food is "novel" if it wasn't used for human consumption to a significant degree in the EU or UK before 15 May 1997. Novel foods must be authorised before they can be placed on the GB market, and the Food Standards Agency maintains the register of what's permitted (FSA, novel foods authorisation guidance).

That matters more than it sounds, because status varies between species that a shopper would think of as interchangeable. The 2026 Nutrients review of cordyceps research notes that Cordyceps militaris is categorised as an unauthorised novel food under the European Commission and EFSA catalogue. Meanwhile Ophiocordyceps sinensis, the species the name "cordyceps" traditionally refers to, was confirmed as not novel for food supplement use (NutraIngredients, August 2025). Same shelf, same common name, different legal footing.

Health claims. This is the one you can see with your own eyes. Under the GB regime, only claims authorised on the Great Britain Nutrition and Health Claims register may be used in commercial communications, and the register lists rejected claims as well as approved ones (GOV.UK, last updated 19 May 2026). Claims that the European Commission hadn't ruled on by 1 January 2021 were carried into the GB register unresolved, which covers a great many botanical and fungal claims.

The practical effect: a UK mushroom brand legally cannot say most of the things you'll read on an American website about the same ingredient. When a British product page sounds hedged and an overseas one sounds confident, that difference is usually regulatory rather than scientific.

5. How strong is the evidence, really?

Here's the honest map. I use four levels, and I'd encourage you to apply them to anything you read about supplements.

1.   Strong evidence. Several randomised trials in humans, repeated by different groups, pointing the same way.

2.   Preliminary evidence. One or two small human trials, or consistent animal data with a plausible mechanism.

3.   Traditional use. A long documented history of use, with little or no rigorous human testing. This is history, not proof of effect.

4.   Anecdotal. Widely reported by users, never properly tested.

 

Functional mushrooms sit at levels 2 and 3 almost entirely. Three examples of what that looks like in practice.

Reishi. Jafari and colleagues (Food Science & Nutrition, 2025) pooled 17 randomised controlled trials covering 971 participants, at doses from 200 to 11,200 mg a day over 1 to 24 weeks. Their GRADE assessment rated the certainty of evidence very low for every outcome they analysed. Some measures shifted, most didn't, and the authors' own conclusion is that the evidence is limited by very low quality.

Cordyceps. Jędrejko and colleagues (Nutrients, 2026) reviewed the human exercise literature and found only 5 intervention studies, 321 participants in total, aged 16 to 35, at doses between 1 and 12 g a day. Not one study reached an overall low risk of bias on the Cochrane RoB 2 tool. Their verdict is that cordyceps use should be treated as investigational rather than evidence-based at this stage.

Lion's mane. The famous trial is Mori and colleagues (Phytotherapy Research, 2009): 30 Japanese adults aged 50 to 80, randomised into two groups of 15, taking dried mushroom tablets for 16 weeks. A very small sample. The lead author worked at a mushroom company's laboratory, which doesn't invalidate the finding but does belong in any honest summary of it. The more recent UK work is Docherty and colleagues at Northumbria University (Nutrients, 2023), who gave 1.8 g daily to 41 healthy adults. They saw faster performance on the Stroop task 60 minutes after a single dose and a non-significant trend on subjective stress after 28 days. Everything else, including word recall, working memory and reaction time, showed nothing. The authors themselves advise caution.

Worth saying once, as an observation about research funding rather than an argument for buying anything: mushrooms are hard to patent, so there's little commercial incentive to fund the large expensive trials that would settle these questions. Absence of large trials isn't the same as evidence of no effect. It also isn't evidence of effect, and I'm not going to pretend otherwise.

One rule I'd ask you to carry away from this section. Evidence attaches to a mushroom, studied at a particular dose, in a particular form. A finished product is a separate object. When any brand, including mine, points at a study, the study belongs to the ingredient and not to the thing in the packet.

6. What's in DoctorShrooms, and the standard we hold it to

We make two gummies.

DoctorShrooms Adults contains 7 functional mushrooms (chaga, lion's mane, cordyceps, reishi, shiitake, maitake and agaricus blazei) plus ginger root and chamomile. Label directions are 3 gummies a day, preferably after breakfast, with new users taking 2 a day for the first 10 days.

DoctorShrooms Kids is for children aged 6 and over and contains 6 functional mushrooms plus the same two botanicals. Label directions are 2 gummies a day after breakfast, with 1 a day for the first 10 days.

Both are gummies rather than capsules or powders, with 0% sugar, organic mushrooms, and a vegan, gluten-free, non-GMO, gelatin-free formula in three natural flavours. Both are third-party tested by Eurofins for potency, heavy metals, contaminants, pesticides and microbial safety. We offer a 30-day money-back guarantee and free UK shipping.

We built both formulas the way we did because we wanted a mushroom gummy we'd be genuinely happy to give our own families, not just one that was legally allowed on a shelf.

Here's what we actually stand behind.

No clinical trial has been run on the finished gummy, only on individual ingredients. What we have tested, independently through Eurofins, is potency and purity.

If you want to try them, [Product link].

7. Questions parents ask us

Are functional mushrooms safe for children?

Our kids' formula is built specifically for ages 6 and over, third-party tested by Eurofins, and comes with clear label directions. Worth knowing honestly: dedicated safety research on functional mushrooms in children specifically is still thin, so as with any supplement, we'd always suggest checking with your GP or pharmacist first, especially if your child takes any prescribed medicine or has an existing condition, the same sensible step worth taking before starting anything new.

Will a mushroom gummy get me or my child high?

No. The species used in functional mushroom supplements contain no psilocybin and aren't psychoactive. They're sold as food supplements under GB food law.

I took a mushroom supplement for a month and felt nothing. What went wrong?

Possibly nothing went wrong, this is a category where results vary a lot between people, and the honest evidence base is still thin. Docherty's 2023 UK study found most cognitive measures didn't shift for most participants either, so a null result is a completely normal one, not a sign you did something wrong. What's worth checking is what you actually took: many products on the market are underdosed relative to the amounts used in research, and there's no legal minimum a "functional mushroom" product has to meet. If you want to give the category a fair test, start with a product that's transparent about species, dose and independent testing, that way you know exactly what you tried.

How much should I take?

For our products, follow the label directions above. For mushrooms in general, I can tell you what doses researchers have used (Mori's participants took roughly 3 g of dried mushroom tablets a day; Docherty's took 1.8 g; the cordyceps studies ranged from 1 to 12 g) but those were specific research preparations in specific study populations, and reporting them isn't me telling you what to take. For dosing decisions about your own health, ask a pharmacist.

Can I just eat mushrooms instead?

For the culinary species like shiitake and maitake, eating them is genuinely good food, there's no reason not to. Worth knowing, though: mushroom cell walls are built largely from chitin, a tough fibre human enzymes can't break down, and it limits how much of a compound like beta-glucan actually gets released during normal digestion. A 2021 study in the Journal of Functional Foods (Colosimo and colleagues) found no beta-glucan was released from white button mushroom during simulated digestion, whether raw or cooked, while a comparable fungal product released more once cooked. It's one lab-based digestion study rather than proof of what happens in every person, and it doesn't mean cooked mushrooms have no nutritional value, they clearly do, just that a whole mushroom and an extract aren't nutritionally interchangeable, which is part of why extraction exists as a separate process. Reishi and chaga are woody and not realistically edible either way, which is part of why they show up as extracts and powders in the first place.

Are "functional mushrooms" and "medicinal mushrooms" the same thing?

The scientific literature does use "medicinal mushroom" as a standard term, so you'll see it in journal papers. UK brands should be careful with it in retail settings, because MHRA Guidance Note 8 assesses medicinal status partly on how a product is presented to consumers, including its name and promotion. Calling a food supplement medicinal invites exactly that assessment.

Conclusion

If you take one thing from this: judge any functional mushroom product on what it tells you about species, form and testing, and treat every health claim you read as something to check against the GB register rather than something to believe. The research on these mushrooms is early and mostly small, the traditional history is long and interesting but isn't proof, and a cautious-sounding UK label is a sign of a brand following the rules. Our own gummies are food supplements that we test through Eurofins and describe as plainly as we can. That's the standard we hold ourselves to.

Research references

Colosimo R, Mulet-Cabero AI, Cross KL, Haider K, Edwards CH, Warren FJ, Finnigan TJA, Wilde PJ. "β-glucan release from fungal and plant cell walls after simulated gastrointestinal digestion." Journal of Functional Foods, 2021;83:104543. Used for: no beta-glucan release from white button mushroom in simulated digestion, raw or cooked; comparable release seen in a cooked fungal protein product.

1.   Mori K, Inatomi S, Ouchi K, Azumi Y, Tuchida T. "Improving effects of the mushroom Yamabushitake (Hericium erinaceus) on mild cognitive impairment: a double-blind placebo-controlled clinical trial." Phytotherapy Research, 2009;23(3):367-372. Used for: trial design and size, 30 participants aged 50 to 80 randomised into two groups of 15, dried mushroom tablets for 16 weeks, and the lead author's mushroom-industry affiliation.

2.   Docherty S, Doughty FL, Smith EF. "The Acute and Chronic Effects of Lion's Mane Mushroom Supplementation on Cognitive Function, Stress and Mood in Young Adults: A Double-Blind, Parallel Groups, Pilot Study." Nutrients, 2023;15(22):4842. Northumbria University. Used for: 1.8 g daily in 41 healthy adults aged 18 to 45, faster Stroop performance 60 minutes post-dose, non-significant stress trend at 28 days, null results on other measures.

3.   Jafari A, Mardani H, Mirzaei Fashtali Z, Arghavan B. "The Nutritional Significance of Ganoderma lucidum on Human Health: A GRADE-Assessed Systematic Review and Meta-Analysis of Clinical Trials." Food Science & Nutrition, 2025;13(6):e70423. Used for: 17 randomised trials, 971 participants, doses 200 to 11,200 mg/day over 1 to 24 weeks, GRADE certainty rated very low across all outcomes.

4.   Jędrejko M, Jędrejko K, Granda D, Kała K, Pokrywka A, Muszyńska B. "Current Evidence of Ergogenic and Post-Exercise Recovery Effects of Dietary Supplementation with Cordyceps militaris in Humans: A Narrative Review." Nutrients, 2026;18(5):781. Used for: 5 human studies, 321 participants aged 16 to 35, doses 1 to 12 g/day, no study at overall low risk of bias, "investigational rather than evidence-based" conclusion, and C. militaris unauthorised novel food status in the EU catalogue.

5.   Food Standards Agency. "Novel foods authorisation guidance." food.gov.uk. Used for: the pre-15 May 1997 significant consumption test, assimilated Regulation (EU) 2015/2283, requirement for authorisation before GB market placement, and the FSA register.

6.   Department of Health and Social Care. "Great Britain nutrition and health claims (NHC) register." GOV.UK, last updated 19 May 2026. Used for: only authorised claims may be used in GB, and the register lists rejected as well as authorised claims.

7.   Department of Health and Social Care. "Nutrition and health claims: guidance to compliance with Regulation (EC) 1924/2006." GOV.UK. Used for: claims undecided by the European Commission at 1 January 2021 require a new GB application.

8.   Medicines and Healthcare products Regulatory Agency. "Guidance Note 8: A guide to what is a medicinal product." GOV.UK, 2026 version. Used for: the presentation test and the mode-of-action test, and the role of packaging, promotion and presentation in classification.

9.   NutraIngredients. "Cordyceps 'boom' on the horizon as novel food status of S. hepiali clarified." 29 August 2025. Used for: Ophiocordyceps sinensis confirmed as not novel, Cordyceps militaris remaining novel.

 

About the author

Kian is the founder of DoctorShrooms, the UK family wellness brand behind properly dosed functional mushroom gummies. Before this, he worked as an engineer on mass spectrometry instrumentation and later as a project manager in aerospace, before leaving to build a brand he felt the market was missing. He writes about functional mushrooms and family wellness, and is not a medical professional. Nothing he writes is medical advice.

Disclaimer: This article is for general information and is not medical advice. Food supplements are not a substitute for a varied, balanced diet and healthy lifestyle. If you have a health condition, are pregnant or breastfeeding, or are giving supplements to a child, speak to your GP or pharmacist first.