Cordyceps and VO2max: what the studies actually found

Cordyceps is the mushroom of the moment in pre-workout powders and "mushroom coffee", usually sold with claims about oxygen use and stamina. Searches like "cordyceps VO2max study" usually lead to the same one or two trials. Here is what they found, and what they did not.

What it is

Cordyceps is a group of fungi that grow on insects. Wild Ophiocordyceps sinensis from the Tibetan plateau is rare and extremely expensive, so supplements almost never contain it. Instead, they use:

• Cs-4 (CordyMax), a fermented mycelium strain derived from Cordyceps sinensis.
• Cordyceps militaris, a related species that is easy to cultivate, often sold as fruiting body or mycelium on grain.

These are different products with different compounds, so a result from one does not automatically transfer to another.

Does it raise VO2max?

The evidence is mixed and comes from small trials:

• Hirsch et al., 2017 (J Diet Suppl). 28 young adults took 4 g a day of a mushroom blend containing Cordyceps militaris or a placebo. After 1 week there was no significant change in VO2max. Ten volunteers continued for 3 weeks, and VO2max rose by 4.8 ml/kg/min in the mushroom group versus 0.9 with placebo. Time to exhaustion also improved. But the 3-week result is based on 10 people, and the product was a blend, so the effect cannot be pinned on cordyceps alone.
• Chen et al., 2010 (J Altern Complement Med). 20 healthy adults aged 50–75 took Cs-4 (333 mg three times a day) or placebo for 12 weeks. Metabolic threshold rose about 10.5% and ventilatory threshold about 8.5% with Cs-4, but VO2max did not change in either group.
• Parcell et al., 2004 (Int J Sport Nutr Exerc Metab). 22 trained male cyclists took 3 g a day of Cs-4 or placebo for 5 weeks. VO2peak, ventilatory threshold and time-trial performance did not change.

So the one study in trained athletes was negative, the one in older adults found threshold changes but no VO2max change, and the positive VO2max result is a short, very small blend trial. That pattern is typical of a supplement whose effect, if any, is small.

Why the marketing outruns the data

Cordyceps marketing often leans on animal studies, traditional use at altitude, and the idea that it improves "oxygen uptake". Human trials are few, small and short, use different products, and rarely repeat each other. Positive results also get far more attention than null ones: the negative cyclist study is rarely cited on product pages. Training status matters too. Untrained people improve on almost any programme, so without careful control of training and a placebo, small gains are hard to attribute to the mushroom.

Does it improve endurance performance?

There is no consistent evidence of better race performance. Threshold changes in older, untrained people are interesting, but lactate threshold also responds strongly to training, which was not tightly controlled in these trials. In the trained cyclists, time-trial results were the same with and without cordyceps.

How it is used in studies

Doses range from about 1 g a day (Cs-4 in older adults) to 3 g (Cs-4 in cyclists) and 4 g of a blend, for 1 to 12 weeks. Many retail products contain far less, or list "mushroom powder" without stating the species, part (fruiting body or mycelium) or active compound content such as cordycepin.

Side effects, safety and anti-doping

Cordyceps was well tolerated in these short trials. The bigger issues are product quality and interactions:

• Contamination and identity. In 2016 Chinese regulators warned that Cordyceps sinensis products contained arsenic well above the limit for functional foods. Mycelium grown on grain may be mostly grain. Ask for third-party testing for identity and heavy metals.
• Interactions. Cordyceps may affect blood clotting, blood sugar and immune function, so take care with anticoagulants, diabetes medication and immunosuppressants.
• Anti-doping. Cordyceps is not prohibited by WADA, but supplements can be contaminated. If you compete, use a third-party tested product (for example, Informed Sport or NSF Certified for Sport).

This page is not medical advice. Talk to a doctor before taking cordyceps if you have a medical condition, are pregnant or breastfeeding, or take medication.

Who might benefit

Possibly older or untrained adults curious about a small effect on thresholds, who accept that the evidence is weak. Trained endurance athletes have the least reason to expect a benefit, based on the only trial in that group.

Bottom line

Cordyceps does not reliably raise VO2max. The positive study is tiny and used a blend, and the trial in trained cyclists found nothing. If you want a higher VO2max, interval workouts and zone 2 training are proven. For racing, caffeine has much stronger evidence. See all supplements and check your fitness with the VO2max calculator.

Sources

• Hirsch KR, Smith-Ryan AE, Roelofs EJ, Trexler ET, Mock MG. Cordyceps militaris improves tolerance to high-intensity exercise after acute and chronic supplementation. J Diet Suppl. 2017;14(1):42–53.
• Chen S, Li Z, Krochmal R, Abrazado M, Kim W, Cooper CB. Effect of Cs-4 (Cordyceps sinensis) on exercise performance in healthy older subjects: a double-blind, placebo-controlled trial. J Altern Complement Med. 2010;16(5):585–590.
• Parcell AC, Smith JM, Schulthies SS, Myrer JW, Fellingham G. Cordyceps Sinensis (CordyMax Cs-4) supplementation does not improve endurance exercise performance. Int J Sport Nutr Exerc Metab. 2004;14(2):236–242.
• Li Y, Liu Y, Han X, Jin H, Ma S. Arsenic species in Cordyceps sinensis and its potential health risks. Front Pharmacol. 2019;10:1471.
• VOA News. China warns of arsenic in cordyceps products (CFDA consumer alert, February 2016). Article