Cordyceps: fungus, formulations and performance claims

Few supplements arrive with a better backstory: a fungus that grows out of a caterpillar high on the Tibetan Plateau, now sold as a tidy capsule for "energy" and "endurance". The backstory is the fun part. The practical part is that "cordyceps" on a shop page can mean at least three different things, each with its own evidence, its own price tag and, in the Netherlands, its own legal position. So let's sort out which fungus is which first; it changes how you read everything else.

Before you add a capsule to the basket

• Three things share the name. Wild Ophiocordyceps sinensis (the caterpillar fungus), cultured mycelium products such as Cs-4, and Cordyceps militaris, the fungus grown commercially in labs and on grain. Studies of one don't automatically describe the others.
• The performance evidence is thin and mixed. One 2025 meta-analysis pooled a few trials of sinensis products and found small gains in endurance measures; a 2026 review of C. militaris found five small studies and no overall low-risk-of-bias trial. Several of the best-known "cordyceps" studies actually tested blends of several mushrooms.
• In the Netherlands, Cordyceps militaris is not allowed in food supplements. The Dutch food authority (NVWA) calls it an unauthorised novel food, inspected 17 businesses in early 2025, took measures against five and advises consumers not to buy it. NVWA describes Cordyceps sinensis as listed as not novel in food supplements. Read on 8 October 2026; rules change.
• No study here tested gaming or screen-based focus, and no dose is recommended. The studies below are described with what they used.

Three fungi, one word

• : What it is; Wild Ophiocordyceps sinensis: The "caterpillar fungus" of the Tibetan Plateau, formerly called Cordyceps sinensis; Cultured mycelium (e.g. Cs-4): A lab-fermented fungal mycelium sold under the sinensis name, with Cs-4 as the best-known example; Cordyceps militaris: A different species, easy to grow on grain, rice or insect pupae
• : Where studies used it; Wild Ophiocordyceps sinensis: Mostly traditional-medicine research; Cultured mycelium (e.g. Cs-4): Many of the older exercise and fatigue trials, such as Parcell 2004 and Chen 2010; Cordyceps militaris: Newer sports trials, often in capsules or in a mushroom blend
• : Things to know; Wild Ophiocordyceps sinensis: A review notes wild material can accumulate arsenic and other metals from high-altitude soils; Cultured mycelium (e.g. Cs-4): The review literature describes these as fermented mycelial products; Cordyceps militaris: In the Netherlands it is not permitted in supplements (see below)

A couple of notes on names. Cordyceps sinensis is the older name for Ophiocordyceps sinensis, and a lot of papers and labels still use it (Panossian, 2026, Pharmaceuticals). The same review says that clinical trials of O. sinensis include both traditional extracts and cultivated mycelial products, and that most fatigue trials used fermented mycelial preparations, most commonly Cs-4. It also describes the wild-harvest arsenic concern. Different papers label the fungus in Cs-4 products differently (one 2026 paper in the Journal of Ethnopharmacology calls the strain Paecilomyces hepiali Cs-4), so if a product says "Cs-4" or "cultured sinensis", it's worth asking which organism it contains.

Where the "7 to 11% VO₂ max" line comes from

You'll often see something like "cordyceps boosts VO₂ max by 7 to 11%". That figure doesn't come from a trial of C. militaris on its own. Here is what the trials report.

• Study: Parcell et al., 2004, Int J Sport Nutr Exerc Metab; Who: 22 endurance-trained male cyclists; What they took: CordyMax Cs-4, 3 g a day for 5 weeks; Result in brief: No change in peak oxygen uptake, ventilatory threshold or time-trial performance; Support: No funder stated in the summary
• Study: Chen et al., 2010, J Altern Complement Med; Who: 20 healthy adults aged 50–75 enrolled; 15 finished; What they took: Cs-4, 333 mg three times a day for 12 weeks; Result in brief: Metabolic threshold up 10.5% (0.83 to 0.93 L/min) and ventilatory threshold up 8.5%; VO₂max itself did not change in either group; the authors call it a pilot; Support: Cs-4 supplied by Pharmanex; partly funded by an NIH training grant
• Study: Hirsch et al., 2017, J Diet Suppl; Who: 28 healthy active adults; 10 continued to week 3; What they took: 4 g a day of a six-mushroom blend (PeakO2); Result in brief: After 3 weeks VO₂max rose in the blend group (+4.8 mL/kg/min) but not placebo; no significant effect at week 1; time-to-exhaustion gains at weeks 1 and 3 show up only in a confidence-interval analysis; Support: Funded by Disruptive Nutrition; blend supplied by Compound Solutions
• Study: Nakamura et al., 2024, Nutrients; Who: 22 male long-distance runners; What they took: C. militaris mycelium extract, 1.8 g a day for 16 weeks; Result in brief: Iron-store marker (ferritin) and creatine kinase differed from placebo; the study was about anaemia markers, not race times; Support: Supported by La Vie En Sante Ltd., which made the supplement; one author works for another company
• Study: Farzan & Koushkie Jahromi, 2026, PLoS One; Who: 12 recreationally active young men; What they took: 1 g of standardised C. militaris extract, once, 30 minutes before a max cycling test; Result in brief: Faster Stroop reaction time after exercise in the extract condition (the overall condition-by-time effect was not significant); resting oxygen uptake higher; peak oxygen uptake unchanged; Support: No specific funding; authors declare no competing interests

Reading across the table:

• The best-known "cordyceps" result isn't cordyceps alone. Hirsch's trial tested a six-mushroom blend (it contained C. militaris, reishi, king trumpet, shiitake, lion's mane and turkey tail, with proportions not disclosed). Only ten people carried on to week three, which is where the VO₂max result appears. That is a result for that blend in a small group.
• The oldest sinensis trials disagree. Parcell's cyclists saw nothing from Cs-4 over 5 weeks; Chen's older adults saw a gain in one threshold after 12 weeks. Different people, different outcomes, different durations.
• The militaris trials ask very different questions. One looked at iron markers, one at a single dose before a max test. Neither is a clean, large test of "does it make you faster".

Two reviews give the wider picture:

• The 2025 athlete meta-analysis leans on very few trials. A systematic review of fungal supplements in athletes (Shu et al., Frontiers in Nutrition) included 14 randomised trials (528 athletes), of which eight went into the quantitative analysis. For Cordyceps sinensis, the pooled results favoured the supplement for endurance performance, ventilatory threshold and VO₂peak, with p-values between 0.03 and 0.05. Its own text counts three cordyceps endurance studies behind that, two positive in runners and one null in cyclists, and it gives preparation (cultivated versus other material) as one possible explanation for the difference. One of the trials was rated at high risk of bias in two areas.
• The 2026 militaris review is cautious. A narrative review (Jędrejko et al., Nutrients) found five studies (321 participants aged 16 to 35, doses of 1 to 12 g a day, some as part of multi-ingredient products). It described the findings as inconsistent, found none with an overall low risk of bias, and said preparations were not standardised or chemically characterised.

Put together: there are hints of endurance benefit from some sinensis preparations, and the claim on the label is bigger than the evidence under it. A gaming or desk-work claim goes further still, because nothing above tested screen-based focus.

Cordycepin, ATP and "cellular energy"

You'll see cordycepin (a compound chemically similar to adenosine) credited for most of the effect. The 2026 Panossian review notes controversy about how much cordycepin reaches the body after oral dosing, and says plasma concentrations after oral use remain in the nanomolar range. Its own reading is that some predicted effects may happen indirectly, so the neat "it feeds your mitochondria" story is a hypothesis for now. Mechanism papers explain why researchers are interested; a trial result is what tells you what happened in people.

Reading a cordyceps label

• On the label: "Cordyceps" with no species; Ask: Which fungus? Sinensis, militaris, or a blend?
• On the label: "Cs-4", "cultured", "mycelium"; Ask: Which organism, grown how, and is it sold in the EU as a supplement?
• On the label: Cordyceps militaris; Ask: In the Netherlands this is a legal question before it is a quality one (see below)
• On the label: Blend of several mushrooms; Ask: The studied blend was one specific product; other blends are different products
• On the label: Cordycepin or beta-glucan percentages; Ask: Those describe composition, not benefit; the trials above didn't link them to results

Our guide to reading supplement labels covers the general habits.

Safety and the Dutch/EU position

Legal status, read on 8 October 2026. NVWA's inspection page on Cordyceps militaris (published 8 September 2025) says it is an unauthorised novel food in the EU, that a company wanting to sell such a supplement must first prove it safe, that this has not happened and so it may not be sold. The page says NVWA checked 17 Dutch businesses between February and April 2025 and took measures against five, which had to withdraw their products. The other 12 either sold C. sinensis or had already stopped selling. NVWA also reported foreign suppliers to other EU countries through the EU food safety alert system, and it strongly advises consumers not to buy C. militaris products (page last modified May 2026). It also says Cordyceps sinensis appears in the EU's novel food status catalogue as "not novel in food supplements" and may be sold (NVWA, Inspectieresultaten Cordyceps militaris 2025). These are NVWA's words about the catalogue, not the catalogue itself, and a national authority's account of its enforcement is not legal advice. In plain terms, a C. militaris supplement sold in the Netherlands falls within the enforcement NVWA describes. Rules in other EU countries can differ in practice, and they can change.

Safety evidence. The athlete meta-analysis notes that side effects such as stomach upset or insomnia weren't consistently recorded across trials, and it cites one runners' trial that reported no evidence of liver toxicity. That is short-term data in healthy people. It doesn't cover pregnancy, long-term use, autoimmune conditions or interactions with prescription drugs, and NVWA says the safety of C. militaris has not been proven. Anyone on medication should check with a pharmacist; our note on supplements and medicines explains why.

Not psilocybin. Cordyceps is a functional mushroom, unrelated to psilocybin mushrooms and truffles.

What to take from the caterpillar fungus

Cordyceps is a fun subject with a tidy story. For endurance, the evidence is a handful of small trials with mixed results and mixed preparations, and the famous VO₂max figures often come from blends or from different fungi than the label suggests. In the Netherlands the species matters for legal reasons as well as scientific ones. A product page that names the fungus, the form and where it is legally sold gives you a proper starting point for comparing.

Where to read next

For the wider picture:

• Functional mushrooms and adaptogens: guide hub, for the six popular ingredients, each with its own guide, and a place to start.
• Fitness and nutrients: the compact guide hub, for the short list of fitness and nutrient guides, from creatine to vitamin D.

Written by Smart Supplements with AI assistance from the sources linked in the text. It has not been reviewed by a clinician.

Last updated: 12 October 2026

This article is for informational purposes only and is not intended as medical advice. Always consult a healthcare professional before starting any new supplement, especially if you take prescription medication.