On November 29, 1918, it was reported from The Hague in Holland that an unnamed Austrian doctor had discovered that beets, the root vegetable, was both an effective preventative and treatment for influenza. Supposedly, he had given his patients a plateful of beet salad just as a fever began to set in and the fever was reduced. 

As word of this simple elixir began to spread, the demand for beets in Holland skyrocketed, causing the price per beet to increase tenfold.

Demonstration at the Red Cross Emergency Ambulance Station in Washington, D.C., during the influenza pandemic of 1918. Library of Congress image.