Your immune system is responsible for helping fight off everything from the common cold to cancer. A tall order!

Send in some reinforcements so it doesn't get battle fatigue. Here are four foods your immune system loves.

Sweet, Creamy, Steamy, Crunchy . . .
Oranges, yogurt, tea, and pumpkin seeds are the order of the day when it comes to giving your immune system a treat, according to RealAge experts Michael Roizen, MD, and Mehmet Oz, MD, authors of the best-selling (and now newly expanded and updated) YOU: The Owner's Manual. Here's how these four superfoods help:

• Oranges are chock-full of vitamin C, an antioxidant vitamin that helps your immune system fend off disease-causing invaders. Other good C options: bell peppers, strawberries, cantaloupe, and broccoli. Or take 400 milligrams of vitamin C three times daily. (Look up more C sources.)
• Yogurt (unpasteurized) contains Lactobacillus acidophilus -- a healthy bacterium that helps thwart fungus-related infections. Or take a 20-milligram acidophilus supplement twice daily.
• Tea is full of flavonoids, powerful vitamin-like substances that reduce immune-system aging. You'll also find them in oats, onions, broccoli, tomatoes, apples, and berries. (Boost your berry intake with this Triple Berry Blender Blaster.)
• Pumpkin seeds are great year round, not just at Halloween, because they contain zinc -- a nutrient that's been shown to help reduce the average length of the common cold. (Find out how zinc can make exercise easier, too.)

Are your immunizations current? Get a checklist with this vaccine assessment.

YOU: The Owner's Manual, Updated and Expanded Edition -- An Insider's Guide to the Body That Will Make You Healthier and Younger. Roizen, M. F., Oz, M. C., New York: HarperCollins, 2008.