TEA

Green and black teas contain high levels of compounds known as catechins and epicatechins. In a Harvard University study, people who drank five cups a day of black tea for two weeks had 10 times more virus-fighting interferon in their blood than others who drank a placebo. The amino acid responsible for this immune boost, L-theanine, is abundant in both black and green tea.

Drink it: Brew for three to five minutes for the optimal antioxidant intake.