Blueberries
Blueberries are one of the healthiest berries we have. It contains anthocyanin, a flavonoid with antioxidant properties. Blueberries are also quite effective against the flu and common cold. Antioxidants prevent the occurrence of oxidation which means it controls and limits the actions of free radicals in the body. The berry boosts your immune system against diseases and prevents the occurrences of chronic illnesses caused by oxidation. Research has also shown that individuals who regularly consume food that contains flavonoids are unlikely to contract upper respiratory tract infections.