Mushrooms
Mushrooms — especially shiitake and oyster varieties — contain beta-glucans, plant compounds shown to activate and modulate immune cell activity.
How to use it:
Sauté in a little oil or ghee, which improves the availability of some of their compounds, and add to stir-fries, soups, or omelettes 2–3 times a week. Mushroom soups are also great way to boost the immunity.