Hype checkGrade C — proceed with skepticism

Cordyceps

A medicinal mushroom with promising but preliminary evidence for improving oxygen utilization and endurance — most human trials are small and short.

By editorialUpdated 2026-05-251 min read

The evidence isn't there yet.

A few small human trials suggest cordyceps (particularly Cordyceps militaris via CS-4) may improve VO2max and time to exhaustion in older or sedentary adults. Results in trained athletes are less convincing, and most studies are short-duration with small sample sizes.

What it's actually good for

Cordyceps is a medicinal mushroom that has been used in traditional Chinese medicine for centuries, and it has attracted modern interest for its potential to improve oxygen utilization and endurance. The mechanistic story is appealing — cordycepin (a bioactive compound in Cordyceps militaris) is an adenosine analog that may enhance cellular ATP production and oxygen efficiency. A few small human trials have shown improvements in VO2max and time to exhaustion, particularly in older or less-trained individuals. However, the evidence base is thin: most studies are short, underpowered, and use varying formulations. In trained athletes, the effects are largely undetectable. This is a C-grade supplement — interesting biology, but you should not expect dramatic performance gains based on current evidence. If you try it, set realistic expectations and use a standardized extract from a reputable source.

Claim-by-claim

Each claim graded independently

The overall grade is the floor. Some claims are stronger or weaker than the headline.

C

Improves aerobic capacity and oxygen utilization during exercise

A few small human trials suggest cordyceps (particularly Cordyceps militaris via CS-4) may improve VO2max and time to exhaustion in older or sedentary adults. Results in trained athletes are less convincing, and most studies are short-duration with small sample sizes.

C

Reduces fatigue and improves energy levels

Animal studies show increased ATP production and delayed fatigue, but human evidence is limited to a handful of trials with mixed results. Mechanisms involving adenosine analogs and mitochondrial support are plausible but not confirmed in rigorous clinical settings.

Sources

2 cited
[01]METACordyceps militaris Improves Tolerance to High-Intensity Exercise After Acute and Chronic SupplementationHirsch KR, Smith-Ryan AE, Roelofs EJ, et al.. J Diet Suppl. 2017
[02]GOVTCordycepsMemorial Sloan Kettering Cancer Center — About Herbs. 2024

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