Elderberry for prevention and treatment of viral respiratory illnesses: a systematic review

Systematic review of randomized and ex vivo studies evaluating elderberry for prevention or treatment of viral respiratory illness and for effects on inflammatory markers. Clinical studies included adults with common cold or influenza, plus healthy volunteers in cytokine studies; one prevention trial and several treatment trials were conducted, along with three cytokine-focused studies.

Oral elderberry was tested in several formulations across the review: proprietary elderberry extract capsules, Sambucol syrup, elderberry lozenges, elderberry infusion/tea, and a single-dose black elderberry tincture. Dosing varied widely, including 300 mg extract capsules 2-3 times/day for 15-16 days, syrup 1 tablespoon 2-4 times/day for 3-5 days, lozenges with 175 mg extract 4 times/day for 2 days, 200 mL/day infusion for 30 days, a single 2.5 g tincture dose, and 500 mg/day anthocyanins for 12 weeks in one ex vivo RCT. One active comparator product also combined echinacea plus elderberry (Echinaforce Hotdrink) given 3-5 times/day for 10 days.

Elderberry may not prevent common cold, but it may shorten colds and influenza illness; overall certainty is low and the evidence is mixed. In the prevention trial, 12/154 in the elderberry group and 17/158 in placebo developed a well-defined cold (RR 0.69, 95% CI 0.34 to 1.39; p = 0.30), but among those who became ill, cold duration was 2 days shorter (MD -2.13, 95% CI -4.16 to -0.10; p = 0.04) and symptom severity was lower (MD -13.69, 95% CI -24.54 to -2.84; p = 0.01). In influenza treatment trials, pooled time to resolution or global improvement was nearly 3 days shorter with elderberry (MD -2.68 days, 95% CI -5.23 to -0.13; 2 studies, 87 participants; I 2 = 94%), and early cure rates were higher at days 2 to 4. One elderberry-echinacea product showed little difference from oseltamivir by day 3 or 5, but may have fewer complications (RR 0.38, 95% CI 0.14 to 1.04) and adverse events (RR 0.82, 95% CI 0.51 to 1.33). No clinical studies reported inflammation-related outcomes; ex vivo and volunteer studies found reductions in cytokine markers without evidence of immune overstimulation.

The evidence base is small, heterogeneous, and mostly low certainty, with widely varying elderberry preparations, doses, durations, and outcomes. Influenza results were very heterogeneous (I 2 = 94%), adverse event ascertainment was inconsistent, and several studies were underpowered or reported incomplete outcome data. Clinical inflammation outcomes were absent, so immune effects are inferred mainly from ex vivo or healthy-volunteer studies rather than patient outcomes.