The world is filled with nasty viruses, bacteria and microbes just waiting to do you in. At the very least, they can cause temporary sickness and misery. Worse, they can make you more vulnerable to killer conditions like cancer.

The good news? You don’t have to take it. Here are 10 simple ways to mobilize your immune system’s illness-fighting forces—the T cells, natural killer cells and antibodies that declare war and act the enemy.

Give yourself a shot against illness. Vaccines aren’t just for kids. Adults need them too. In fact, there are 10 vaccine-preventable diseases adults can protect themselves against, such as hepatitis B (for adults with diabetes or who are at risk for hepatitis B) and measles, mumps and rubella.

Except for the flu shot, which is recommended yearly for adults age 19 and older, many of the vaccines require only one or two doses over the course of a lifetime. Protecting yourself safeguards others. It’s now recommended that adults, especially those in close contact with infants younger than 12 months, such as parents, grandparents, babysitters and nannies, get the Tdap (tetanus, diphtheria, and pertussis) vaccine and a booster every 10 years after that. For a complete list of the vaccines for adults, visit the CDC at http://www.cdc.gov/Features/AdultVaccines/.

Get some shut eye. Studies suggest that sleep deprivation causes sluggish production of natural killer cells, a type of white blood cell that can obliterate certain microbes and cancer cells. A study in the Archives of Internal Medicine found that catching a cold is more likely if you sleep less than seven hours a night. All 153 participants in the study were given a solution containing live rhinovirus (a common cold virus). Those who slept eight hours or more each night were three times less likely to catch the cold.

Overall, your best bet is to aim for a solid eight hours of sleep each night, says Merrill Mitler, Ph.D., program director at the Neuroscience Center at the National Institute of Neurological Disorders and Stroke in Bethesda, Maryland. If that’s not possible, nap if you can, and be sure to catch up on lost sleep on the weekends.

Don’t avoid all fat. A diet rich in omega-3 fatty acids (found in fatty fish like salmon) may help reduce your body’s production of eicosanoids from omega-6 fatty acids, hormone-like substances that can over-stimulate your immune system, says Artemis Simopoulos, M.D., founder and president of the Center for Genetics, Nutrition and Health in Washington, D.C. That might explain why high levels of eicosanoids are associated with autoimmune conditions such as rheumatoidarthritis, diverticulitis, multiple sclerosis and lupus, which occur when an hyper alert immune system attacks the body’s own cells as a ‘foreign invader.’ To up your diet’s omega-3 intake, eat fish two at least two times a week, says Dr. Simopoulos, echoing the recommendation of the American Heart Association.

Pile on the produce. A healthy diet has the power to prevent heart disease, diabetes, hypertension, gastrointestinal disorders and some forms of cancer. Only 25 percent of U.S. children and adults consume the minimum recommended intakes of vegetables, according to the United States Department of Agriculture. As a general rule, half of your plate should be fruits and vegetables. “Focus on eating more produce in whatever way it’s convenient for you,” says Marisa Moore, R.D., L.D., a spokesperson for the American Dietetic Association.

Minimize nutrient loss during cooking by steaming or microwaving veggies in a small amount of water until just tender-crisp.

Guard against weight gain. Research showsthat obesity may alter your immune system response. Add to that the many health risks associated with being overweight (including heart disease, diabetes and sleep apnea), and avoiding the 20- to 30-pound gain that many adults pack on as they age becomes an important way to safeguard your well-being, says Madelyn H. Fernstrom, Ph.D., founding director of the Weight Management Center at the University of Pittsburgh Medical Center.

The number you don’t want to hit: a body mass index (BMI) of 25 or higher, which is considered overweight. To determine your BMI, log onto http://nhlbisupport.com/bmi/bmicalc.htm, the Web site for the National Heart, Lung and Blood Institute.

Exercise your options. Doing moderate workouts (like walking or jogging) for at least 30 minutes five or more times a week can increase the circulation of immune-boosting natural killer cells in your body, even when you’re at rest, according to Susanna Cunningham-Rundles, Ph.D., research professor of immunology in pediatrics at the Weill Cornell Medical College in New York City.

But overdosing may work against you. The stress of intense exercise (approximately 75 minutes or more at a strenuous pace, or anything that makes you feel as if you’re pushing yourself too hard) may stimulate stress hormones like cortisol, which some studies suggest can suppress natural killer cells. The upshot? If you’re a long-distance runner or serious athlete, you may be at increased risk for colds and flu. Take other stay-healthy steps, like getting plenty of sleep, eating a well-balanced diet and asking your doctor about a flu shot, recommends Cunningham-Rundles.

Don’t get caught dirty handed. Get in the habit of coughing and sneezing into your sleeve or elbow and teach your kids to do the same. Cold and flu viruses spread from person to person in spray droplets (sneezing) or when germ carriers cough or sneeze into their hands, then touch, say, the TV remote or the phone. Also be sure to wash your hands often, especially before eating and after using the bathroom, changing a diaper and touching raw meat, poultry, fish or eggs. Handwashing is one of the most effective ways to prevent microbes that cause colds, flu and foodborne illness from entering your body. If soap and water aren’t available, hand sanitizer will do.

Take a breather. Evidence suggests that unmanaged stress sets off a chain of hormonal events that can decrease the activity of natural killer cells, says Gailen Marshall, M.D., Ph.D., director of the division of allergy and immunology at the University of Mississippi Medical Center in Jackson. Runaway stress can also make you susceptible to colds and aggravate chronic conditions such as asthma and allergies. “Recognize your limitations and give yourself permission to have time just for you,” Marshall advises. Schedule in at least 20 minutes of daily down time and find a fun hobby.

Get more zinc. If you feel a cold coming on, try a zinc-based cold remedy, such as Cold-Eeze. “It can help boost your immune system to lessen the duration of a cold and severity of symptoms,” says Bob Stout, a pharmacist in Candia, N.H. Cold-Eeze works by sealing the receptors on cells so that cold viruses can’t enter and replicate. For best results, start the treatment —pop a lozenge or give yourself two spritzes of the oral spray version—within 24 to 48 hours of the onset of symptoms.

Don’t go it alone. Can you name someone who’d help you in a pinch? Do you have a confidante? Answering yes puts you at lower risk for illness, particularly heart disease, says Marty Sullivan, M.D., director of the Healing the Heart Program at the Duke Center For Living in Durham, N.C.

Studies show that people who have a diverse social network (including friends, family, coworkers and others) have greater resistance to colds, too. But don’t just “friend” someone on Facebook. Strengthen your connections by meeting in person occasionally for coffee or a fun night out.