Eating the following has been shown to help boost your immune system and can prevent illness and long term health issues: Vitamin C-rich foods, like citrus fruit and broccoli, Vitamin E-rich foods, like nuts and whole grains, Garlic, Zinc-rich foods, like beans, turkey, crab, oysters, and beef, Bioflavanoids, which are found in fruits and vegetables, Selenium-rich foods, like chicken, whole grains, tuna, eggs, sunflower seeds, and brown rice, Carotenoid-rich foods, like carrots and yams, Omega-3 fatty acids, found in nuts, salmon, tuna, mackerel, flaxseed oil and hempseed oil.