Almonds & Seeds: Heart-healthy almonds provide the immune-boosting antioxidant vitamin E, which reduces your chances of catching colds and developing respiratory infections. Other sources of vitamin E include fortified cereals, turnip greens, and wheat germ.

Colored Bell Peppers: These are rich in vitamin C. Some studies show that vitamin C can reduce the intensity and duration of colds and flu. One cup of colored bell peppers provides 200% of your daily vitamin C needs!

Dark chocolate: Cocoa contains a chemical called theobromine, which helps the body fight common cold symptoms. Dark chocolate is also rich in magnesium, a mineral that boosts immunity.

Citrus Fruits: Findings show that flavonoids, found in the soft white skin of citrus fruits, boost immune system activation. Flavonoids are also present in grapefruits, oranges, lemons, limes, and other fruits and vegetables.

Mushrooms: Mushrooms are rich in selenium, which helps white blood cells produce cytokines (immune function cells), and beta-glucans—an antimicrobial type of fiber that activates cells to find and destroy microbes.

Proteins are essential to help your body build immune cells. Lean meat, poultry, fish, legumes, dairy, eggs, nuts, and seeds are good sources of protein. High-protein foods are rich in other healing nutrients, such as vitamins B6, B12, selenium, and zinc, which contribute to a healthy immune system.

Garlic: Garlic contains the phytochemical allicin, an antimicrobial compound. A British study found that people taking allicin supplements experienced 46% fewer colds and recovered faster than those who did not take the supplement.

Tea: Researchers at Harvard University found that drinking tea improves the body's immune defense system, likely due to theanine, an immunity-boosting amino acid. Tea also contains catechins, which act like a cleanup crew against free radicals. Drink one to three cups of black, green, or white tea every day.

Tomato: Tomatoes contain a carotenoid known as lycopene, which improves the body's defenses. Cooked tomatoes, such as those in pasta sauce, become heart-healthier and boost their cancer- and infection-fighting abilities because cooking substantially increases the levels of the beneficial compound lycopene. Recent findings show that regular consumption of a high-lycopene tomato sauce helps reduce bad cholesterol (LDL) levels in the blood.

Fatty Fish: In a recent study, participants with the lowest vitamin D levels were about 40% more likely to report a recent respiratory infection than those with higher levels. Salmon, along with other fatty fish like sardines and tuna, contains high amounts of omega-3 fatty acids (which have inflammation-fighting properties) and vitamin D. Replace red meat and processed meats, such as bacon and deli meats, with fish and fatty fish.