POWER FOODS TO BOOST IMMUNITY

It takes more than an apple a day to keep the doctor away. It turns out that eating some pretty surprising nutrients will help keep your immune system on guard. You can ensure your body and immunity run smoothly by rounding out your plate with plenty of colorful servings of fruits and veggies, plus 8 to 10 glasses of water a day, at the very least. The following ingredients can add extra flu-fighting punch to your winter meal plan.

YOGURT: Probiotics, or the "live active cultures" found in yogurt, are healthy bacteria that keep the gut and intestinal tract free of disease-causing germs. Although they're available in supplement form, a study from the University of Vienna in Austria found that a daily 7-ounce dose of yogurt was just as effective in boosting immunity as popping pills. Be sure to pick up containers free of excess added sugar. Plain varieties (which you can flavor with cinnamon and fresh fruit) are your best bets, but anything with less than 8 total grams of sugar is still a wholesome option. Your optimal dose: One 7-ounce serving daily.

OATS AND BARLEY: These grains contain beta-glucan, a type of fiber with antimicrobial and antioxidant capabilities more potent than echinacea, reports a Norwegian study. When animals eat this compound, they're less likely to contract influenza, herpes, even anthrax; in humans, it boosts immunity, speeds wound healing, and may help antibiotics work better. (These flu home remedies are also worth reading up on.) Your optimal dose: At least one of your three daily servings of whole grains.

GARLIC: This potent onion relative contains the active ingredient allicin, which fights infection and bacteria. British researchers gave 146 people either a placebo or a garlic extract for 12 weeks; the garlic takers were two-thirds less likely to catch a cold. Other studies suggest that garlic lovers who chow more than six cloves a week have a 30% lower rate of colorectal cancer and a 50% lower rate of stomach cancer. Your optimal dose: Two raw cloves a day and add crushed garlic to your cooking several times a week.

CHICKEN SOUP: When University of Nebraska researchers tested 13 brands, they found that all but one (chicken-flavored ramen noodles) blocked the migration of inflammatory white cells—an important finding, because cold symptoms are a response to the cells' accumulation in the bronchial tubes. The amino acid cysteine, released from chicken during cooking, chemically resembles the bronchitis drug acetylcysteine, which may explain the results. The soup's salty broth keeps mucus thin the same way cough medicines do. Added spices, such as garlic and onions, can increase soup's immuneboosting power. Your optimal dose: Have a bowl when you're feeling crummy. (Give this delicious chicken soup recipe a try!)

TEAS: People who drank 5 cups a day of black tea for 2 weeks had 10 times more virus-fighting interferon in their blood than others who drank a placebo hot drink, in a Harvard study. The amino acid that's responsible for this immune boost, L-theanine, is abundant in both black and green tea-decaf versions have it, too. Your optimal dose: Several cups daily. To get up to five times more antioxidants from your tea bags, bob them up and down while you brew.

FORTIFIED CEREALS: Not a meat person? Many fortified bowls of cereal pack an entire day's worth of zinc. For example, a serving of Kellogg's Smart Start or General MillsWhole Grain Total, has about 15 mg of the mineral. For a point of comparison, a 3-ounce serving of beef has about 7 mg of zinc. Your optimal dose: Aim for one bowl daily-especially if you relate to any of these six signs you're not getting enough zinc.

ORANGE FRUITS AND VEGGIES: 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, MD, director of theYale-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, like sweet potatoes, carrots, squash, canned pumpkin, and cantaloupe. Your optimal dose: A half-cup serving only carries 170 calories but packs 40% of the daily recommended intake of vitamin A (in the form of beta-carotene). MUSHROOMS: 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 1 ounce a few times a day for maximum immune benefits. Add a handful to pasta sauce, sauté with a little oil and add to eggs, or heap triple-decker style on a frozen pizza.

KEFIR: In an 80-day Swedish study of 181 factory employees, those who drank a daily supplement of Lactobacillus reuteria specific probiotic that appears to stimulate white blood cells-took 33% fewer sick days than those given a placebo. Though not every brand of kefir uses this specific strain, many Lifeway products do, including their Perfect12 and Lowfat Kefir beverages. Your optimal dose: Try working kefir into your diet at least a few times per week.

FATTY FISH:Salmon, mackerel, and herring are rich in omega-3 fats, which reduce inflammation, increasing airflow and protecting lungs from colds and respiratory infections. One animal study also found that the nutrient may help ward off various strains of the flu. (Check out these 20 amazing salmon recipes for some great ideas for preparing your next fish dinner.) Your optimal dose: Consume two or three 4-ounce servings per week. In you're pregnant or breastfeeding, avoiding eating shark, swordfish, king mackerel, and tilefish, which are high in mercury