Mushrooms: Deficiency of selenium in mushrooms may increase infection risk, according to a Nutrients study. The immune system benefits from mushroom riboflavin and niacin.

Sweet potatoes: Beta-carotene is found in sweet potatoes, carrots, squash, and pumpkin. Vitamin A in this form helps your skin fight bacteria and viruses.

Almonds: Almonds are rich in vitamin E, another immune-boosting antioxidant. A handful 1/4 cup provides 50% of your daily vitamin E.

Yogurt: Yogurt contains active probiotic microorganisms. These boost immunity and keep our guts and digestive tracts clean of disease-causing microorganisms.

Leafy greens: A study in The Journal of Immunology found that leafy greens like spinach and kale are high in fiber, antioxidants, and folate, which boosts immunity.

Tea: Antioxidant polyphenols and flavonoids in green and black tea combat disease. L-theanine, an immune-boosting amino acid, is found in black and green tea.

Cabbage: This affordable winter vegetable contains glutamine, which multiple studies, including one in Nutrients, have shown to boost the immune system. Use shredded raw cabbage in winter soups and stews or wraps and salads for a crunchy texture without changing the flavor.

Garlic: In addition to repelling vampires, garlic contains allicin, an antibiotic and antifungal agent.