Ingestion of Okinawa Island Vegetables Increases IgA Levels and Prevents the Spread of Influenza RNA Viruses.

Background: It has been hypothesized that flavonoid ingestion stimulates immunity, promotes health, and prevents human illness. The aim of this analysis was to evaluate the association of the levels of immunoglobulin A (IgA) with the prevention of influenza infections and with the polyphenols contained in Okinawan vegetables.

Methods: IgA, immunoglobulin G (IgG), immunoglobulin M (IgM), and soluble interleukin-2 receptor (sIL-2R) levels were measured in 44 outpatients who regularly ingested vegetables grown on Okinawa Island (200-300 g/day for ≥ 300 days/year) with no history of influenza infection and in 73 patients who ingested the vegetables irregularly or not at all with a history of influenza infection.