Vitamin D Is Key to a Healthy Immune System, and These 7 Foods Have It in Spades

If you're keeping fortified orange juice on hand, know that one 8-ounce glass gives your body a whopping 15 percent of the daily value of vitamin D, along with 100 percent of your daily vitamin C. What's more, 100 percent orange juice contains a natural plant chemical, or flavonoid, that may offer health benefits to humans. In fact, data suggests that among those who consumed flavonoids, there was a 33 percent decrease in upper respiratory tract infections, compared with those who did not consume flavonoids.