Nakamura A., Shinozaki E., Suzuki Y., Santa K., Kumazawa Y., Kobayashi F., Nagaoka I., Koikawa N. Effect of the Administration of Cordyceps militaris Mycelium Extract on Blood Markers for Anemia in Long-Distance Runners. Nutrients. 2024;16(12):1835.
Rationale
During preseason training, long-distance runners often develop "sports anemia" from sweat iron losses and hemolysis from impact loading. The authors tested whether Cordyceps militaris mycelium extract (used in Japan as a substitute for Ophiocordyceps sinensis) could maintain ferritin, hemoglobin and hematocrit while reducing muscle-damage markers.
Methods
Design — placebo-controlled double-blind parallel comparison. Population: 22 healthy male long-distance runners, students at Juntendo University (Chiba, Japan), aged 18–24 (mean 19.7±0.9 in the placebo group, 20.2±1.1 in CM). Exclusions: baseline anemia, iron or other "anti-anemia" supplements, recent blood donation. Intervention: C. militaris mycelium extract or placebo daily for 16 weeks of preseason training. All 22 completed the product protocol. Endpoints: trajectories of serum ferritin, hemoglobin, hematocrit and creatine kinase (CK) at weeks 0, 4, 8, 12 and 16; secondary — 5,000 m time (2 participants, one per group, missed this test and were excluded only from that analysis).
Results
The rate of serum-ferritin change in the CM group moderately rose while in the placebo group it declined; the between-group difference was statistically significant at weeks 4 and 8 (p<0.05). Rates of change of hemoglobin and hematocrit were significantly higher in the CM group versus placebo at week 8 (p<0.05). CK levels were above normal at baseline in both groups; at week 16 the rate of CK change in the CM group was significantly lower than placebo (p<0.05), indicating less accumulated muscle damage by preseason's end. No serious adverse events are reported in the annotation.
Conclusions
The authors conclude that C. militaris mycelium extract during preseason can maintain hemoglobin and hematocrit in long-distance runners, presumably by suppressing the decline of iron stores (reflected in ferritin), while exerting a protective effect against muscle damage as measured by creatine kinase.
Worth noting
A pilot-scale study: n=22, all young male athletes from one university team, limiting external validity. The ferritin effect was recorded at weeks 4 and 8, but its rate of change (not the absolute level) is a proxy, and links to clinically meaningful outcomes (subjective fatigue, performance) were not assessed. The authors give no dietary iron-intake data and do not state whether training volume was standardized between groups — critical because differing loads could explain part of the CK difference. The active group received C. militaris extract, not O. sinensis: the authors justify this by the absence of O. sinensis's natural host in Japan, but it means results cannot automatically transfer to classical "cordyceps" in the traditional sense. Finally, 5,000 m time showed no significant between-group difference (per the article text), so an "improved performance" conclusion does not follow from this study's formal athletic outcomes — only from anemia and muscle-damage lab markers.