Make vitamin C your friend. Many people start to guzzle orange juice when they’re already sick because vitamin C is known for its immune-boosting powers. This vitamin is effective at reducing the severity and duration of upper respiratory illnesses. It typically works best if you have adequate stores of vitamin C before you get sick.
This handy list of fruits and vegetables that are all high in vitamin C. A one-cup serving of any of these foods provides at least 100 percent, and in many cases quite a bit more, of the daily value of the vitamin. Keep in mind: Eat all of these foods raw as vitamin C is destroyed by cooking.
Citrus fruits (oranges, grapefruit) Guava Kale Kiwi Papaya Pineapple Strawberries
Bell peppers (green, yellow and red) Broccoli Brussels sprouts Cabbage Cantaloupe
Both tea and garlic have been clinically shown to help people avoid colds and flu. Black and green tea contain antioxidants called catechins, while garlic contains allicin, which produces antioxidants when digested, which may be the reason for helping ward off viruses.