You get a flu shot every fall, take a daily multivitamin and load up on zinc as soon as the sniffles start. But if you think that's enough to keep you healthy, you're wrong. "Your physical well-being is affected by almost every aspect of your lifestyle," says Roberta Lee, M.D., medical director of the Continuum Center for Health and Healing at Beth Israel Medical Center in New York City. "How much you sleep at night, how high your stress level is, how you deal with anger, what you do or don't eat -- these all have a profound impact on how effective your immune system is."
And it's your immune system -- an intricate network of the thymus, spleen, lymph nodes, white blood cells and antibodies -- that wards off bacteria and viruses and helps your body cope with any invasion of disease. When that system is weakened, you're not only more susceptible to illnesses and ailments, but also less able to fight them once they get a foothold, says Lee.
That's why it's so important to tackle bad habits and negative emotions now that break down immunity. To get you started, we've put together a list of six habits that sabotage your ability to stay well, together with advice about how to fix them and set yourself on the road to lasting health.
"I'll make that dental appointment next week."
Immune-system saboteur: Procrastination
A study at Carleton University in Ottawa, Ontario, Canada, found that people who procrastinated in their everyday lives also put off medical treatment and had worse health than nonprocrastinators. "The faster you deal with a health problem, the better the outcome tends to be," says study co-author Timothy A. Pychyl, Ph.D. Delaying or completely neglecting treatment, as procrastinators often do, may prolong your ailment -- and that can weaken your immune system, making you more susceptible to other illnesses.
Immunity booster: Procrastinators tend to avoid tasks that seem overwhelming; their goal is to circumvent the stress of dealing with something at that moment, says Pychyl. To make your "to-do's" more manageable, he suggests switching from goal-oriented intentions to implementation-oriented ones -- in other words, instead of thinking big picture ("I can't be sick -- I need to be in top shape for my race next week!"), simply focus on your next step ("I'm going to make a doctor's appointment this afternoon").
"I want to lose 10 pounds fast, so I'm limiting myself to three mini-meals a day."
Immune-system saboteur: A too-low-calorie diet
A diet that's very low in calories doesn't provide the body with the nourishment it needs, and without adequate nutrients, cell functioning is impaired, compromising the immune system, explains Cindy Moore, M.S., R.D., a Cleveland-based spokeswoman for the American Dietetic Association and director of nutrition therapy at The Cleveland Clinic Foundation. "Drastically reducing calories is not an effective way to lose weight. Only a sensible diet and exercise can do that," adds Margaret Altemus, M.D., an associate professor of psychiatry at Cornell University's Weill Medical College in New York City, who specializes in the body's response to stress. What's more, not getting enough of certain vitamins (especially some B vitamins) can cause symptoms of depression, which have been linked to heart disease and other physical problems.
Immunity booster: Do your best to take a more realistic view of your body. "Too many women want to be 10 or 15 pounds thinner than what's natural for them, and often sacrifice their health as a result," says Altemus. Whether or not you're trying to lose weight, always strive to eat balanced meals and snacks that provide enough calories to keep you energized.
To figure out the bare minimum of daily calories you need (the amount you should never drop below), Moore suggests using this quick formula: Divide your weight in pounds by 2.2, then multiply that number by 0.9; multiply the resulting number by 24. If you're sedentary, multiply the number you got above by 1.25; if you're mildly active, multiply it by 1.4; and if you're moderately active, multiply by 1.55. For a woman who weighs 145 pounds, the calculation would be: 145 --: 2.2 = 65.9; 65.9 x 0.9 = 59.3; 59.3 x 24 = 1,423. Assuming she's mildly active, she would multiply 1,423 by 1.4, which translates to a minimum of 1,992 calories a day.
A lack of energy and irregular or light menstrual periods are indications you may not be eating enough. A nutritionist can help you plan your meals wisely so you get enough calories and nutrients while still taking off extra pounds; for a referral, call the American Dietetic Association at (800) 366-1655 or visit eatright.org.
"I work 10-hour days, I take evening classes and I'm remodeling my house -- I feel like my head's exploding!"
Immune-system saboteur: Chronic stress
A little bit of stress can actually improve immune function; your body senses the stress, and ups its antibody (aka immunoglobulin: proteins that fight bacteria, viruses and other invaders) count to compensate -- at least temporarily.
But chronic stress leads to a drop in antibodies, which weakens your resistance to infection, says Lee, who adds that as little as three or more days of extreme stress can increase your risk of memory impairment, menstrual irregularities, osteoporosis and diabetes.
Immunity booster: Everyone responds differently to stress; what feels like an overwhelming load to one woman may seem like small potatoes to another. If you feel overwhelmed, exhausted or just plain run-down, you probably are dealing with unhealthy amounts of stress. Flare-up of a chronic condition like psoriasis or asthma also could be stress-related. So it's imperative to take steps to rid your life of situations -- a bad job, a bad relationship -- that cause you unreasonable amounts of anxiety or concern.
"I get by on five hours of sleep during the week -- but I make up for it on the weekend."
Immune-system saboteur: Not getting enough rest
During sleep, your immune system revs up and repairs itself. But when you skimp on your z's, you deprive your body of this much-needed renewal, says Lee. In fact, a 2003 study in the journal Psychosomatic Medicine found that individuals who missed a night of sleep after receiving a hepatitis A vaccine produced fewer antibodies than did well-rested individuals who also got the vaccine, then went to bed at their usual bedtime.
Immunity booster: Aim for eight hours of sleep a night, says Joyce Walsleben, R.N., Ph.D., director of the Sleep Disorders Center at New York University School of Medicine in Manhattan. "Some women need more or less than that; experiment until you find the amount that leaves you feeling well-rested throughout the day," she suggests. Stop drinking caffeine around noon, and aim to avoid alcohol at least three to four hours before bed, because both can interfere with the quality of your slumber.
If you're getting enough sleep and still feel exhausted during the day, talk to your doctor; it could be that you're suffering from a sleep disorder -- such as sleep apnea (airway obstruction during sleep) or restless-legs syndrome -- that causes wakefulness.
"I love to exercise -- I hit the gym seven times a week, two hours at a time."
Immune-system saboteur: Working out too much
Exercising for 30 minutes daily has been shown to improve activity in white blood cells, which scavenge for bacteria and viruses. But working out too long -- and too hard -- can have an opposite effect: Your body begins to perceive the extreme activity as a state of stress, and your immunoglobulin count drops. "Ninety minutes or more of high-intensity exercise results in a drop in immune function that can last up to three days," says Roberta Lee. "That may be why so many marathoners end up sick after their races" -- although the same holds true for those of us who aren't professional athletes. In addition, long periods of exercise may contribute to vitamin depletion, which can lead to illness too.
Immunity booster: If you plan to go strong the entire time you work out, limit your sessions to less than an hour and a half. "Be reasonable," says Lee. "Try to fit in half an hour to an hour of moderate-intensity cardio, and then if you want to keep going, 20 minutes of weights." If you relish extended weekend time at the gym, make sure your workout includes an activity that is low in impact and intensity -- like yoga, Pilates or easy swimming.
"My sister really made me mad when she asked if I'd gained weight. I haven't spoken to her in two months."
Immune-system saboteur: Holding a grudge
A study published in Psychological Science found that when participants mentally rehashed a situation where another person had hurt them, and nursed their grudge against that person, they experienced a surge in blood pressure and an increase in heart rate and negative feelings -- classic symptoms of stress, which are linked to immune-system problems. While the long-term effects of these symptoms have not yet been studied, "they [could] eventually lead to a physical breakdown," speculates study author Charlotte vanOyen Witvliet, Ph.D., an associate professor of psychology at Hope College in Holland, Mich.
Immunity booster: Forgive, forgive, forgive! When participants in the Hope College study focused on forgiving the person who'd hurt them, the benefits were clear and immediate: They became calmer and felt more positive emotions and more in control.
Witvliet stresses that forgiving others involves remembering the event without feeling angry about it -- but not necessarily forgetting what upset you. "It's not a matter of tolerating, excusing or condoning someone's behavior. And reconciliation may be inappropriate if the individual who's harmed you has proven to be abusive or untrustworthy," Witvliet explains. "The key is to honestly acknowledge your hurt feelings, then let go of any bitterness or vengeance toward that person."