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By CARIN GORRELL, SELF Nutrition Director

You probably know that washing your hands regularly and getting enough sleep is important when it comes to warding off bugs, but did you know that what you eat can also play a key role in boosting your immunity? SELF's nutrition director gives us the skinny on what to munch on to stay healthy this season.

Skim Milk: About one-third of Americans are deficient in vitamin D, which is found in fortified milk, yet this nutrient is key to defending against germs: If your D levels are low, your white blood cells won't be able to react to or ward off infections effectively. Aim to get 600 international units a day. Great sources include fortified milk, orange juice and yogurt, as well as egg yolks and wild salmon.

Red Bell Pepper: You probably think of citrus fruits when it comes to getting more immune-boosting vitamin C, and it's true they're a good source of the nutrient. But surprise-red bell peppers have almost three times the C of an orange! In fact, just half of one pepper will deliver the recommended 75 milligrams per day for women ages 19 and up (guys, take an extra bite or two-you need 90 mg a day). Dip pepper slices in hummus for an afternoon snack or toss it in a stir-fry for dinner.

Tea: Wake up to a steaming mug of tea to ramp up your body's defenses against infection: A study from Harvard University reveals that the immune cells of tea drinkers responded to germs five times faster than those of coffee drinkers. And green tea, specifically, contains an antioxidant compound called EGCG which works with your immune system to ease inflammation. Add a squirt of lemon to up the ante. The juice contains quercetin, which also has anti-inflammatory powers.

Yogurt: Probiotics, the healthy bacteria in yogurt, have been linked to strong immune systems and a lower risk for gum disease and even some cancers. But not all yogurts have enough of the good stuff. The National Yogurt Association's Live & Active Cultures seal appears on some cartons that do (such as Yoplait). Add honey for a lift. It contains prebiotics, a carb that helps yogurt's bugs thrive.

Goat cheese: This creamy spread contains copper, which helps keep your immune system humming. Plus it's packed with flavor, so a little goes a long way without adding unwanted calories to your meal or snack (an ounce contains only 76 calories and 4 grams of saturated fat). Try swapping out mayo in favor of a smear goat cheese on a sandwich or wrap, or mix the cheese with chopped nuts and dried fruit for a filling toast topper.

Blueberries:  All berries are good for you, but those with a blue hue are among the best of the bunch. They have the highest levels of disease-fighting antioxidants of all commonly consumed fruit, according to research from the USDA Agriculture Research Service in Little Rock, Arkansas. The vitamin C in blueberries also blunts the effects of stress by reducing free radicals and bolstering your immune system.

Pumpkin Seeds:  This tasty snack has zinc, a mineral that jacks up the immune system by inhibiting viral replication. The seeds have also been shown to reduce the duration of cold symptoms. But know that too much zinc can suppress your immune system, so stick with the recommended daily intake: Women ages 19 and up need 8 mg a day; men need 11 mg. For their part, pumpkin seeds have about 2 grams per ounce (142 seeds); try them on your yogurt or oatmeal for a little crunch or add them to a healthy trail mix.

Mushrooms: You already know that eating any fruit or vegetable regularly is a good thing for your health, but when it comes to germ defense, mushrooms have an edge. Research suggests that the fungus may have antiviral and antibacterial properties. Any type will do the trick, but if you're still looking to up your intake for immunity-strengthening vitamin D, button mushrooms are a potent source.

Broccoli: A compound in this leafy green may enhance your immune system, an animal study in The Journal of Nutritional Biochemistry shows. Chewing the veggie triggers the release of chemicals, possibly helping your body regulate infection-fighting white blood cells. Cooking reduces the dose, so it's best to eat them raw.

Pasta: Skimping on carbs or fat? Some people on plans that severely limited carbs (think Atkins) or fat (Ornish) missed out on vital nutrients like iron and zinc that help maintain immunity and energy, research from Stanford University shows. A healthy source that supplies both: whole-grain pasta. What a perfect excuse to order Italian tonight!

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