Doctors in a flu study believe that the antioxidant flavonoids in elderberry bind to flu virus particles to prevent the virus from infecting cells or reproducing. About 70 people who experienced flu-like symptoms for less than 24 hours took 700 mg of elderberry extract in four 175 mg doses per day or a placebo. Symptoms included fever, headache, muscle aches, nasal congestion and discharge, and coughing.
After 48 hours, none in the placebo group had recovered and symptoms in most had stayed the same or worsened. For the elderberry group, 60 percent reported one or two minor symptoms while another 28 percent were symptom-free.