Jung S.J., Hwang J.H., Oh M.R., Chae S.W. Effects of Cordyceps militaris supplementation on the immune response and upper respiratory infection in healthy adults: a randomized, double-blind, placebo-controlled study. J Nutr Health. 2019;52(3):258–267.
Rationale
Cordyceps is a classic "immunomodulator" of East Asian tradition, and supplement marketing routinely sold it as "cold protection." Yet before this work no study had tested the actual clinical outcome — URI incidence — in humans. A Korean team (Chonbuk National University Hospital) asked directly: does C. militaris extract reduce the frequency and severity of colds in people with recurrent infections?
Methods
A 12-week randomized double-blind placebo-controlled study: 100 healthy adults aged 20–70 who had suffered ≥2 colds in the previous year. Diary registration of URI episodes and symptoms + lab panel: NK-cell activity, IgA, cytokines (IFN-γ, IL-2), standard safety biochemistry and hematology. Conducted under Chonbuk IRB with support from Korea's Rural Development Administration.
Results
- Clinical outcome: URI frequency and severity in the cordyceps group did not differ from placebo — a null result on the main question.
- Lab markers: NK-cell activity significantly higher (p = 0.047) and IgA significantly higher (p = 0.035) versus placebo at week 12.
- Safety: biochemistry panels (AST, ALT, GGT, ALP, CK and others) and hematology without clinically meaningful differences.
Conclusions
The authors' formulation is maximally honest: possible immunomodulatory effects exist at the level of lab markers, but protection against URIs in these conditions was not demonstrated. NK activity and IgA rose — and the subjects did not fall ill any less often.
Worth noting
Strengths: a real clinical outcome (diary-recorded URI episodes), not only surrogates; double blinding and placebo; n=100 — large for the field; full safety panel with published tables.
Limitations:
- The main result is negative — immune markers without a clinical correlate do not prove an "anti-cold" effect.
- Self-reported URIs by diary without laboratory confirmation of episodes.
- One extract from one manufacturer — standardization not detailed; transfer to other products is limited.
- 12 weeks within a specific season — results may have depended on that season's baseline viral load.