Not just any hot tea, though. Chamomile, according to researchers from London's Imperial College, is the one that'll help prevent sickness. In a recent study, they found people who drank five cups of the brew a day for 2 weeks had increased blood levels of plant-based compounds called polyphenols, some of which have been associated with increased antibacterial activity. Levels remained high for 2 weeks after subjects stopped drinking the tea, says lead researcher Elaine Holmes, Ph.D. Bonus: chamomile tea also raised levels of glycine, a mild nerve relaxant and sedative.