Mushrooms & Drug Interactions
7 CYP isoforms
Reishi triterpenoids inhibited all 7 major cytochrome P450 enzyme types in a 2024 systematic screen, but whether typical supplement doses reach the concentrations needed for that inhibition remains an open question.
Li et al., Frontiers in Pharmacology, 2024
66
reishi triterpenoids screened for CYP enzyme activity
77
clinical mushroom-drug studies with no adverse pharmacokinetic effects
In vitro only
all CYP inhibition data; no human pharmacokinetic confirmation yet
Li et al., Frontiers in Pharmacology, 2024
View as image ↗Most discussions of medicinal mushroom safety include a line about "possible drug interactions" and move on. What they rarely address is the specific mechanism: which mushrooms affect which liver enzymes, how strong that evidence is, and whether any of it is confirmed in humans. A 2024 study in Frontiers in Pharmacology provided the most detailed answer yet for reishi, mapping 66 of its compounds against seven cytochrome P450 enzyme types and confirming some of those interactions in live rats. Understanding what those results mean, and what they don't, starts with understanding what cytochrome P450 does.
This article covers the cytochrome P450 drug metabolism research specifically. For the full picture of how medicinal mushrooms interact with blood thinners, diabetes medications, and immunosuppressants, see the complete guide to medicinal mushrooms and drug interactions. For the underlying science of how mushroom compounds are extracted and absorbed, the extraction methods guide covers bioavailability in detail.
Key Takeaways
- A 2024 systematic screen tested 66 reishi triterpenoids against 7 cytochrome P450 isoforms; CYP1A2 was the most frequently inhibited enzyme across all compounds tested
- One specific reishi compound inhibited CYP3A4, 2B6, 2C9, and 2C19 simultaneously, with IC50 values of 4.78 to 25.28 μM in laboratory conditions
- Li et al. (2024) ran a rat pharmacokinetic experiment and confirmed that these in vitro inhibitory effects produced real changes in drug blood levels in animals
- A 2020 systematic review of 77 clinical studies found that combining turkey tail or reishi with cytotoxic chemotherapy produced no significant pharmacokinetic interactions
- Kozarski et al. (2019) found that reishi and lion's mane inhibited platelet aggregation in vitro, a separate drug interaction mechanism that operates independently of the CYP450 system
- The central unanswered question: in vitro inhibitory concentrations are often 10 to 100 times higher than what typical supplement doses achieve in human plasma
What Cytochrome P450 Does, and Why It Matters for Drug Metabolism
Your liver contains a family of enzymes called cytochrome P450, often abbreviated CYP450. Their job is to chemically modify substances that pass through your bloodstream, breaking drugs down, converting some into their active forms, and preparing them for excretion. About 70% of all prescription medications pass through this system.
Different CYP enzymes handle different drugs. CYP3A4 is the busiest, handling roughly half of all drugs that go through the CYP system. CYP2C9 metabolizes warfarin, ibuprofen, and several diabetes medications. CYP2D6 processes many antidepressants and antipsychotics. CYP1A2 handles caffeine, certain antidepressants, and some antibiotics.
When a compound inhibits one of these enzymes, the drug that enzyme normally processes builds up in the bloodstream. The prescribing physician's intended dose gets exceeded, because the drug is breaking down more slowly than expected. For most drugs, a modest elevation in blood concentration isn't dangerous. For drugs with narrow therapeutic windows, where the difference between a therapeutic dose and a toxic dose is small, even a modest inhibitor can tip things out of range.
This is why researchers test supplements against CYP enzymes. Inhibition is the most common mechanism by which botanical compounds produce unexpected interactions with medications. The question for mushrooms is whether any of them inhibit CYP enzymes at concentrations that are actually reached inside the human body after a normal supplement dose.
The 2024 Ganoderma Study: 66 Compounds, 7 Enzymes, and What Was Actually Found
Li et al. published the most systematic CYP450 study of any mushroom species to date in Frontiers in Pharmacology in 2024.[1] The team took 66 triterpenoids isolated from Ganoderma lucidum (reishi) and tested each one against seven CYP isoforms: CYP1A2, 2A6, 2B6, 2C9, 2C19, 2D6, and 3A4. This is not a study of a whole reishi extract but of specific purified compounds, which allows precise measurement of which molecules are responsible for any observed effects.
CYP1A2 was the most commonly inhibited enzyme across the 66 compounds. Most individual triterpenoids showed activity against at least one isoform; the pattern across the full compound set suggests that CYP1A2 inhibition is not limited to one unusual molecule but is a relatively common property across reishi's triterpenoid family.
The study's most specific finding involved a compound called compound 25. In laboratory conditions, compound 25 inhibited four CYP isoforms simultaneously: CYP3A4, CYP2B6, CYP2C9, and CYP2C19. The IC50 values, the concentration needed to cut enzyme activity in half, ranged from 4.78 μM for the most potent inhibition to 25.28 μM for the least. These are precise, measurable values. They are also laboratory values.
Li et al. did not stop at cell culture results. The study included a rat pharmacokinetic experiment to test whether these in vitro inhibitory effects produced real changes in drug concentration when the compounds were administered alongside CYP-metabolized drugs. In rats, they did, confirming that the interactions found in laboratory dishes translated to a living biological system, at least in animals.
This rat data matters. A purely in vitro finding carries limited weight because many compounds inhibit enzymes in a dish without producing effects in a whole organism with absorption, distribution, and metabolism working simultaneously. Rat confirmation raises the level of biological plausibility. It does not, on its own, establish what happens in humans at supplement doses.
The Dose Problem: Why Lab Results Don't Automatically Translate to People
The IC50 values from Li et al. (4.78 to 25.28 μM) are concentrations measured in a laboratory system. To know whether those concentrations matter, you would need to know what concentration of reishi triterpenoids actually reaches the liver in a person taking a typical supplement dose.
That data is largely unavailable. Human pharmacokinetic studies of individual Ganoderma triterpenoids (the specific compounds, in humans, showing blood and tissue concentrations after oral supplementation) are not part of the published literature captured in this study.[1] What is known from botanical pharmacology more broadly: oral bioavailability of large, lipophilic triterpenoid molecules is often low. First-pass metabolism through the gut wall and liver removes a significant fraction before the compound reaches systemic circulation. The plasma concentrations of any specific triterpenoid at a 1 to 3 gram reishi supplement dose are likely far below the IC50 values measured in vitro.
Many pharmaceutical-grade CYP inhibitors, drugs specifically designed and dosed to block these enzymes, achieve meaningful inhibition at plasma concentrations well under 1 μM. Compounds that require 4 to 25 μM to produce half-inhibition in a dish face a high bar for clinical relevance unless they concentrate particularly well in liver tissue.
None of this means the Li 2024 findings are unimportant. A study that maps 66 compounds against 7 enzymes and confirms effects in live animals is exactly the kind of mechanistic data that should inform precautionary thinking for people on narrow-window medications. What it isn't is evidence of confirmed drug interactions in people taking normal supplement doses. Those are different claims, and distinguishing them is the honest reading of this research.
CYP3A4 Handles Half of All Drugs. Reishi Inhibits It in the Lab.
CYP3A4 is the enzyme most people on long-term prescription medications should understand, because the list of drugs it metabolizes is vast. Statins that lower cholesterol (simvastatin, atorvastatin, lovastatin). Benzodiazepines used for anxiety (diazepam, alprazolam, midazolam). A large portion of cancer chemotherapy agents. Immunosuppressants used in organ transplant patients (cyclosporine, tacrolimus). Many HIV antiretroviral drugs. Some calcium channel blockers for blood pressure.
Compound 25 from Li et al.'s study inhibited CYP3A4 in vitro, with an IC50 value within the 4.78 to 25.28 μM range reported across the four isoforms that compound targeted. Other reishi triterpenoids in the same screening showed varying levels of CYP3A4 activity.[1]
The drugs most vulnerable to CYP3A4 inhibition are those with narrow therapeutic windows, where the difference between the intended blood level and a toxic blood level is small. Cyclosporine, used by organ transplant patients to prevent rejection, is the most cited example. Modest increases in cyclosporine blood concentrations can cause kidney damage. Modest decreases risk rejection. Prescribers monitor cyclosporine levels closely precisely because so many factors affect CYP3A4 function.
If reishi at supplement doses meaningfully inhibited CYP3A4 in the human liver, cyclosporine concentrations could shift unpredictably. This mechanism is the basis for caution in herb-drug interaction databases, even though it rests on in vitro evidence rather than confirmed clinical cases. For a dedicated look at these concerns, see Mushrooms and Immunosuppressants: Safety Considerations.
Warfarin Uses the Enzyme Reishi Inhibits Most Specifically
The CYP2C9 inhibition finding in Li et al. is particularly relevant for one drug: warfarin.[1]
Warfarin is one of the most widely prescribed anticoagulants in the world. It has one of the narrowest therapeutic windows of any commonly used medication. Too little, and blood doesn't thin enough to prevent clots. Too much, and serious bleeding becomes a risk. Prescribers monitor warfarin patients with regular INR blood tests, a measure of how quickly blood clots, because an enormous number of foods, drugs, and supplements can shift it.
CYP2C9 is the primary enzyme responsible for clearing warfarin from the body. Compound 25 from Li et al.'s study inhibited CYP2C9 in laboratory conditions, with an IC50 value within the 4.78 to 25.28 μM range documented across the four isoforms that compound affected. If that inhibitory effect occurred in a warfarin patient at supplement doses, warfarin metabolism would slow, warfarin blood concentrations would rise, and INR would increase, meaning blood would thin more than the prescriber intended.
This mechanism is why warfarin appears so prominently in herb-drug interaction discussions around reishi. The concern is mechanistically grounded in CYP2C9 inhibition data. It is not confirmed by controlled clinical trials showing that reishi actually raises INR in warfarin patients.
There is also a separate mechanism by which mushrooms might affect people on anticoagulants that has nothing to do with CYP enzymes. Kozarski et al. (2019) tested extracts from multiple mushroom species directly against human platelet activity in vitro and found that reishi and lion's mane both reduced platelet aggregation, the clumping of blood cells that initiates clot formation.[2] This antiplatelet effect would add to the effects of anticoagulant drugs by a completely independent pathway. For a detailed look at mushrooms and anticoagulant medications, see Mushrooms and Blood Thinners: Interaction Risks.
What 77 Clinical Studies Found When Turkey Tail and Reishi Met Chemotherapy
Against this backdrop of in vitro concerns, there is a significant body of clinical data for one specific context: medicinal mushrooms combined with cancer chemotherapy.
Lam et al. (2020) published a systematic review in Chinese Medicine examining 213 studies of mushroom-drug combinations, 77 of which were clinical studies in cancer patients.[3] The mushrooms studied were Yunzhi (turkey tail, Coriolus versicolor) and Lingzhi (reishi, Ganoderma lucidum) combined with a range of cytotoxic chemotherapy agents.
The consistent finding across these 77 clinical studies: adding turkey tail or reishi to chemotherapy reduced the immunosuppression that chemotherapy causes, improved white blood cell counts, and in several studies improved survival and quality of life. No adverse pharmacological interactions were reported.
Critically, the Lam review included two pharmacokinetic studies that specifically tested whether turkey tail polysaccharide (PSK) changed the blood concentration of the chemotherapy drug Tegafur. Those pharmacokinetic studies found no significant interaction: PSK did not affect how Tegafur was absorbed, distributed, or metabolized.
This is genuinely reassuring data. The same reishi and turkey tail preparations whose compounds show CYP inhibitory activity in vitro apparently did not cause measurable pharmacokinetic problems when combined with chemotherapy in real patients across 77 clinical studies. That could mean that in vitro concentrations required for inhibition simply aren't achieved at supplement doses. It could also mean that the chemotherapy drugs in these studies were not the most sensitive indicators of CYP function, or that the specific compounds most active in the Li 2024 screen are not the predominant compounds in the extracts used in the Lam 2020 studies.
What the Lam 2020 data does not do is resolve the question for narrow-window drugs like warfarin or cyclosporine, which have far less clinical data and far smaller safety margins.
A Second Pathway: How Mushrooms Can Affect Blood Thinning Without CYP Involvement
The CYP450 mechanism is not the only way mushroom compounds could interact with medications. Kozarski et al.'s 2019 study adds a second pharmacological pathway that operates independently.[2]
Kozarski and colleagues tested water-based and alcohol-based extracts from multiple mushroom species against human platelet aggregation in cell culture. Platelet aggregation is the process by which blood cells stick together to form the initial plug when a vessel is injured. It is the first step in clot formation. Reishi and lion's mane extracts both inhibited this process. The inhibitory effect varied by species and by extract type, and all results were in vitro.
This matters for people taking antiplatelet medications such as aspirin, clopidogrel (Plavix), and ticagrelor, all of which work by reducing platelet activity. Adding a supplement that also reduces platelet activity creates additive antiplatelet effects. The two effects compound each other, increasing bleeding risk, without involving the CYP450 enzyme system at all.
Two distinct mechanisms for two distinct types of medication concern: CYP enzyme inhibition (affecting drug blood levels for any drug metabolized by CYP enzymes) and direct antiplatelet activity (adding to the effects of drugs that reduce platelet clumping). Understanding which mechanism is relevant depends on which class of drug someone is taking.
Reishi Has the Most Evidence. Here's Where Other Species Stand.
The evidence base for CYP450 inhibition is not evenly distributed across mushroom species. Based on the studies reviewed:
Reishi (Ganoderma lucidum) has by far the most specific CYP450 data. Li et al.'s 2024 systematic screen of 66 reishi triterpenoids is the most detailed study of any mushroom species against the CYP enzyme family. Reishi also appears in the platelet aggregation data from Kozarski et al. as a species with demonstrated antiplatelet activity in vitro. For drug interaction concern specifically through the CYP pathway, reishi has the most mechanistic evidence of any mushroom species.
Lion's mane (Hericium erinaceus) appears in Kozarski et al.'s platelet aggregation data, showing antiplatelet activity in vitro. CYP450-specific data for lion's mane is limited compared to reishi, and no equivalent systematic screen of lion's mane compounds against CYP isoforms appears in the current literature.
Turkey tail (Coriolus versicolor) has the most actual clinical pharmacokinetic data of any mushroom species: two studies within Lam et al.'s systematic review specifically examined turkey tail PSK and a chemotherapy drug, finding no significant pharmacokinetic interaction. That clinical record is reassuring, with the caveat that the drugs tested may not capture the full picture for narrow-window CYP substrates.
Cordyceps, chaga, maitake, and shiitake have less specific CYP450 research in the current literature. Cordyceps has documented cardiovascular and blood-modifying effects but less specific enzyme inhibition data; see Cordyceps Side Effects: What the Safety Research Shows for what the safety evidence covers.
The absence of specific CYP data for a species is not evidence that no interaction exists. It is simply an unanswered question.
The Bottom Line
Reishi triterpenoids inhibit multiple cytochrome P450 enzymes in cell culture, with Li et al.'s 2024 systematic screen of 66 compounds against 7 isoforms providing the most detailed data published for any mushroom species. An animal pharmacokinetic experiment in the same study confirmed that these inhibitory effects translate to real changes in drug blood levels in rats. The central unresolved question is whether typical human supplement doses achieve the tissue concentrations needed for meaningful CYP inhibition. A 2020 systematic review of 77 clinical studies found no pharmacokinetic interactions when turkey tail and reishi were combined with chemotherapy, suggesting some reassurance for that context. Reishi and lion's mane also show direct antiplatelet activity in vitro, creating a second, independent interaction mechanism relevant to people on anticoagulant or antiplatelet drugs.
Frequently Asked Questions
Sources & References
- 1RTHM-01926·Li, Dawei et al. (2024). “Triterpenoids from Ganoderma lucidum inhibit cytochrome P450 enzymes interfering with the metabolic process of specific clinical drugs..” Frontiers in pharmacology.Study breakdown →PubMed →↩
- 2. Source details for this reference are not yet available.
- 3RTHM-01225·Lam, Chun Sing et al. (2020). “Herb-drug interactions between the medicinal mushrooms Lingzhi and Yunzhi and cytotoxic anticancer drugs: a systematic review..” Chinese medicine.Study breakdown →PubMed →↩