Zinc deficiency is one of the most common nutritional shortfalls among American adults, especially for vegetarians and those who've cut back on beef, a prime source of this immunity-bolstering mineral. And that's unfortunate, because even mild zinc deficiency can increase your risk of infection. Zinc in your diet is very important for the development of white blood cells, the intrepid immune system cells that recognize and destroy invading bacteria, viruses, and assorted other bad guys, says William Boisvert, Ph.D., an expert in nutrition and immunity at the Scripps Research Institute in La Jolla, California.
Your optimal dose: A 3-ounce serving of lean beef provides about 30 percent of the Daily Value (DV) for zinc. That's often enough to make the difference between deficient and sufficient. Not a beef person? Try zinc-rich oysters, fortified cereals, pork, poultry, yogurt, or milk.
You may not think of skin as part of your immune system. But this crucial organ, covering an impressive 16 square feet, serves as a first-line fortress against bacteria, viruses, and other undesirables. To stay strong and healthy, your skin needs vitamin A. "Vitamin A plays a major role in the production of connective tissue, a key component of skin," explains Prevention advisor David Katz, M.D., director of the Yale-Griffin Prevention Research Center in Derby, Connecticut. One of the best ways to get vitamin A into your diet is from foods containing beta-carotene (like sweet potatoes), which your body turns into vitamin A.
Your optimal dose: A half-cup serving, which delivers only 170 calories but 40 percent of the DV of vitamin A as beta-carotene. They're so good, you might want to save them for dessert! Think orange when looking for other foods rich in beta-carotene: carrots, squash, pumpkin, and cantaloupe.
For centuries, people around the world have turned to mushrooms for a healthy immune system. Contemporary researchers now know why. "Studies show that mushrooms increase the production and activity of white blood cells, making them more aggressive. This is a good thing when you have an infection," says Douglas Schar, DipPhyt, MCPP, MNIMH, director of the Institute of Herbal Medicine in Washington, DC.
Your optimal dose: Shiitake, maitake, and reishi mushrooms appear to pack the biggest immunity punch; experts recommend at least ¼ ounce to an ounce a few times a day for maximum immune benefits. Add a handful to pasta sauce, or sauté with a little oil and add to eggs.
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