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Carrots and sweet potatoes

Orange fruits and vegetables, such as carrots and sweet potatoes, are rich in beta-carotene. When we eat these foods, our bodies convert this organic compound into vitamin A, which is essential for maintaining a strong immune system.

Vitamin A is especially important for areas that go haywire when we catch a cold: It keeps the mucous membranes that line our nose and throat—one of the body's first lines of defense—healthy and functioning properly.

Next: Sunflower seeds