If your have a healthy immune system, it tags every pathogen for destruction—be it a virus, fungus, or rogue cell bent on becoming cancerous. It does this by churning out 10 million proteins called antibodies every single hour. This kind of vigilance and fighting power demands a plentiful supply of nutrients.
Poor diet is the biggest cause of a weakened immune system in healthy individuals,” says William Boisvert, PhD, an expert in nutrition and immunity at The Scripps Research Institute in La Jolla, CA.
While an all-around healthy diet is the key to stronger immunity, these particular immune system-boosting foods can keep you in fighting condition.
1. Beef: reinforce your weak spots
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, Dr. Boisvert explains.
A 3-oz serving of lean beef (enough to make a respectable, but not decadent, roast beef sandwich) provides about 30% of the Daily Value (DV) for zinc. That’s often enough to make the difference between deficient and sufficient. Just can’t stomach beef? Try zinc-rich oysters, fortified cereals, pork, poultry, yogurt, or milk.
2. Sweet Potatoes: Tighten your borders
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 David Katz, MD, director of the Yale-Griffin Prevention Research Center in Derby, CT.
One of the best ways to get vitamin A into your diet is from foods containing beta-carotene, which your body turns into vitamin A. One of the quickest, most delicious ways to get beta-carotene? Serve candied sweet potatoes (canned are fine). Each 1/2-cup serving delivers only 170 calories but 40% 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, canned pumpkin, and cantaloupe.
3. Mushrooms: Rev up white blood cells
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.
Shiitake and maitake mushrooms, now available fresh in US supermarkets, appear to pack the biggest immunity punch. They’re easy to use too. Just add a handful to pasta sauce, sauté with a little oil and add to eggs, or heap triple-decker style on a frozen pizza. Good news for absentminded chefs: “Basically, you can burn them, and they will still powerfully stimulate the immune system” says Schar.[pagebreak]
4. Tea: Clean up dangerous debris
Like all wars, the war on germs is messy business. When your healthy immune system knocks off invaders and then begins to repair whatever damage they’ve done, it creates some potentially damaging compounds itself (called free radicals) that can damage your cells and their DNA, accelerating aging and setting the stage for diseases such as cancer.Antioxidants can mop up those free radicals before they do their dirty work. Fruits and vegetables are loaded with antioxidants, but both black and green teas are higher in antioxidants than any fruit or vegetable. So pour yourself a restorative cup of this “antioxidant broth.”
Get the most from each sip by bobbing your tea bag up and down while you brew. In recent studies, jiggled tea bags released five times as many polyphenols, the powerful antioxidants in tea, as sedentary ones.
5. Kefir: Send in the reinforcements
The mucosal membrane lining your intestinal tract is home to trillions of good bacteria that keep harmful germs from invading via your intestinal wall. Unfortunately, antibiotics can wipe out these good bacteria, leaving you vulnerable to those unwelcome, diarrhea-causing germs.
You can send in diet reinforcements by eating yogurt or drinking a delicious fermented milk drink called kefir. Brands that contain active cultures are good sources of healthy bacteria that can repopulate your gut. “Early studies suggest that cultured foods such as kefir and yogurt enhance the immune response and overall health,” says Ruth DeBusk, PhD, RD, of the Digestive Disease Clinic in Tallahassee, FL. Kefir has a smooth, creamy texture and, at 160 calories per cup, makes a refreshing dessert.