In plain terms: Cordyceps (Cordyceps sinensis / militaris) shows early signals in human research but the evidence is limited -- small trials, surrogate endpoints, or not yet independently replicated. It is an emerging area, not yet a proven one.
Cordyceps (Cordyceps sinensis / militaris)
The evidence as the record states it
Parcell et al. (International Journal of Sport Nutrition and Exercise Metabolism, 2004; PMID 15118196): 5-week randomized placebo-controlled trial of CordyMax Cs-4 in endurance-trained cyclists; VO2peak and time-trial performance did not change. Chen et al. (J Altern Complement Med, 2010; PMID 20804368): 12-week randomized placebo-controlled pilot, 20 healthy adults aged 50 to 75, Cs-4 1 g/day; the metabolic threshold rose 10.5 percent and the ventilatory threshold 8.5 percent, with no change in VO2max. Shu et al. (Front Nutr, 2025; PMID 41280379): systematic review and meta-analysis of 14 randomized trials of fungal supplements in 528 athletes, 8 pooled; Cordyceps sinensis improved endurance performance (P=0.05), ventilatory threshold (P=0.03) and VO2peak (P=0.04), with low heterogeneity; read in full in October 2026: the VO2peak and ventilatory-threshold pools rest on three Cordyceps sinensis trials, Parcell 2004 (PMID 15118196; null), a 2021 Thai crossover in 12 runners published in a journal PubMed does not index and rated at high risk of bias by the reviewers (positive on VO2max), and a 2022 Brazilian trial in 22 amateur marathoners in a journal PubMed does not index (5 km time improved, VO2max and thresholds unchanged). The pooled VO2peak gain is carried by the one high-risk trial. Trials of mushroom blends containing Cordyceps militaris are not evidence for cordyceps alone. Grade C: the two named Cs-4 trials found no change in VO2max, and the 2025 pooled VO2peak gain rests on one small high-risk trial. Mixed, thin randomized evidence.
Why Grade C and not Grade B
Grade C reflects early or limited human evidence -- small trials, surrogate endpoints, or preliminary findings not yet independently replicated. The evidence points in a promising direction but does not yet meet the standard for Grade B. A single well-powered, independently replicated trial with a meaningful endpoint would move this to Grade B or higher.
What would move this grade
A well-powered randomized trial with an objective, clinically meaningful primary endpoint and at least one independent replication would support Grade B or higher.