Eat Plenty of Protein
Your body needs protein to make white blood cells, which are the backbone of the immune system. Many protein-rich foods, including lean meat and fish, provide other immunity-boosting nutrients, too, such as B vitamins, iron, omega-3 fatty acids and zinc. So pile on the protein, making sure you have some at every meal. A sample day's worth might be 8 ounces of yogurt at breakfast, a cup of beans with salad for lunch, a handful of almonds for a snack and 3 ounces of chicken during dinner.
See recipe: Sauteed Chicken with Sage
Load Up on Immune-Boosting Fruits and Vegetables
In addition to protein, it's also essential to eat a good mix of produce to ensure you get an array of nutrients. Aim to get your daily 8 to 9 servings of fruits or vegetables, which could help to reduce the risk of a cold by about 25 percent, according to research. Aim for at least two colors per meal. One veggie to add: shiitake mushrooms, which might increase natural killer T cells.
See recipe: Mushroom Ragout with Polenta
Stock Up on Fish
Eat mackerel, salmon or tuna at least twice each week. Such fatty varieties of fish are rich in omega-3s, which might reduce your risk of respiratory infection, probably by boosting levels of virus-fighters such as helper T cells.
See recipe: Roasted Salmon with Pea Puree
Pick the Right Supplements
The drugstore might be full of so-called immunity boosters, but there's strong evidence for only two of them: vitamin D and probiotics. One large study found that people low in vitamin D were 40 percent more likely to become ill. Because it's difficult to get enough D from food, you need a supplement. Most doctors recommend 10,000 international units daily.
When it comes to probiotics, try a daily over-the-counter supplement; take as directed. It might slash your risk of an upper respiratory infection by about 12 percent.