Evidence Level
Moderate
Elderberry has compelling clinical evidence for respiratory infections. Hawkins et al. (2019) published a meta-analysis showing substantial reductions in cold and flu duration across 4 RCTs. Tiralongo et al. (2016) conducted a randomized, double-blind, placebo-controlled trial of 312 air travelers and found that elderberry supplementation significantly reduced cold duration and symptom severity in those who became ill. The antiviral mechanism has been elucidated by Roschek et al. (2009), who demonstrated that elderberry flavonoids directly bind influenza virus proteins, blocking cell entry. While the evidence base is smaller than for vitamin C or zinc, the effect sizes in existing trials are notably large.