New flu strains. Antibiotic-resistant tuberculosis. Germs in and on the foods we buy in supermarkets and in restaurants. Flesh-eating bacteria. Feels like you’re in the midst of a scary twenty-first century germ invasion. And while you try your best to keep from meeting the nastiest bugs, there’s only so much you can do without living in a bubble. That means boosting your immune system matters more than ever.

And steps you take to boost your immunity may also protect you from the chronic diseases associated with aging. See, immunity busters -- everything from aging and stress to lack of sleep, too little exercise, and not-so-smart eating -- can pull the plug on how well your white blood cells, natural killer cells, and chemical messengers can attack and destroy foreign invaders. Didn’t know you had an army of defenders, did you? Well, you do. And the very same actions that lessen their ability to fight off bugs also cause trouble by encouraging chronic inflammation -- a hot-button health risk now linked with asthma, heart disease, diabetes, and even some types of cancer.

Keeping your own personal security force strong and disciplined is easy:

Feast on fin food. EPA (eicosapentaenoic acid), the essential omega-3 fatty acid found in fatty fish (and fish oil, of course), limits several cellular processes (involving dendritic cells and interleukin 12; aren’t you glad you asked?) associated with inflammation, so they can’t do their dirty work. Serve yourself salmon or trout at least twice a week, or get 2,000 milligrams of EPA plus DHA, another omega-3, from supplements daily. Don’t like the fishy taste or the size of the pill? Just get the DHA from pills made from algae -- that’s where the fish get it.

See red or go nuts. Red wine, red grapes, and peanuts are great sources of resveratrol, a compound that protects against immune system aging and inflammation. Are resveratrol supplements worth taking? Here's what the docs say.

Learn the art of ahhhh. Your nervous system and your immune system are linked more closely than fraud and Bernard Madoff. Extreme stress reduces your natural killer cell count -- one reason widows and widowers are more likely to get sick after the death of a spouse. Even periods of short stress (say, road rage) can boost levels of proinflammatory chemicals called cytokines. Set aside 10 minutes a day for relaxation, whether it’s meditation, intimacy, a walk, or the pure bliss of playing with your kids or grandkids. And learn some coping skills that help you talk your stress level down while you’re still in traffic or whatever situation gets on your nerves. Here are a few fast ways to let go of stress.

Tuck yourself in. Sleep deprivation torpedoes immunity and increases levels of proteins associated with inflammation. Stop shortchanging yourself and jump into the sack a half hour earlier tonight . . . and every night this week. Add another half hour next week, and keep going until you’re getting 7 1/2 to 8 hours of shuteye per night. Every night!

Take a walk today. Regular physical activity can help keep immunity where it should be. You don’t have to be a gym rat: When a group of overweight couch potatoes started exercising five times a week, they gained a definite cold-fighting edge over nonexercisers. Create a 20-minute workout to your liking with this tool.

Pop some vitamin D. This vitamin can’t do its immunity-boosting job if you don’t get enough of it . . . which includes at least 30% to 40% of us. Since it’s difficult to get what you need from food alone, get 1,000 international units a day from a supplement if you’re younger than 60, 1,200 if you’re 60 or older. Find out how vitamin D might help you live longer, too.

Munch apples, broccoli, and red onions. All are bursting with quercetin, a flavonoid that shores up immunity, even when you’re fatigued. The fiber and antioxidants in these natural goodies also help reduce or mute inflammation instigators. These four other foods will help pump up your immune system, too.

Think zinc. Go to the end of the alphabet for a mineral that supports immunity (it may also thwart cancer cells). You can get the zinc you need -- 12 milligrams a day -- from crab, oysters, pork, poultry, beans, cashews, and yogurt. Or find a good multivitamin with less than 15 milligrams. Too much of the stuff could stop other important minerals from doing their jobs.

Don’t forget classic "C." This vitamin helps you produce more bullets to kill invading germs. Bell peppers are chock-full of vitamin C; other good C options include strawberries, cantaloupe, and broccoli. Or take 400 milligrams of vitamin C as a supplement three times a day. Does vitamin C have a slimming effect, too? Here's the answer.