But you might have noticed that colds, flus, and other seasonal blights seem to hit some people again and again, while others coast through to spring unscathed. Is this punishment random, like a tornado, or is there a method to the cold-and-flu madness?
There is indeed a method. While we can all help prevent viral and bacterial infections by washing hands regularly and avoiding germ-laden surfaces, it's not just the bugs we encounter that determine how healthy we are. Our well-being also depends on how prepared our bodies are to fight them.
Increasingly, scientists are discovering that the way we live our lives can affect whether we succumb to illness -- from the common cold to more serious conditions. "A healthy immune system helps protect the body from disease, infection, and even some kinds of cancer," says Ronald Stram, M.D., physician and founder of the Center for Integrative Health and Healing in Delmar, New York.
What's more, new research shows that the immune system is more complex than originally thought. "The old way of thinking was immune system as closed loop, or an isolated group of defenses," says Sarosh Motivala, assistant professor at the UCLA Cousins Center for Psychoneuroimmunology. Instead, it's "a very integrated process" involving many body systems, along with our brains. Diet, sleep habits, exercise levels, and state of mind all influence how our immune cells work.
Staying infection-free therefore requires not only using soap and water (don't neglect those) but also paying attention to your overall state of wellness. Here, we explain how your everyday routines might be dragging down your immune system, and how to shift those routines for optimal health.
Balance is Key
Understanding how the immune system works is the first step to improving it. At its most basic, it tries to block viruses, bacteria, fungi, and parasites -- collectively called pathogens -- from entering the body. The skin and soft tissue lining the respiratory, gastrointestinal, and vaginal tracts form natural barriers to pathogens, and good bacteria on these surfaces help keep harmful invaders out.
When something slips through these defenses, the so-called "innate immune system" (which we're born with) rises to action, with specialized cells swallowing up invaders and destroying them. That process releases chemical signals that spur the next line of attack: the adaptive immune system (which we develop throughout our lives), which takes on specific invaders and "remembers" past encounters so the body can respond quickly the next time an old foe invades.
And it goes beyond cold and flu viruses. Scientists now believe that this surveillance system may also be directed against cancer cells within the body, helping the body recognize and eliminate them and keeping tumors from growing further. (Some researchers believe it may be possible to harness the immune system to fight cancer, or at least to encourage tumors to remain dormant.)
You might assume that boosting the immune response is always a good thing, but that's not actually the case. In fact, an overactive immune system can prove harmful. Autoimmune diseases such as lupus and rheumatoid arthritis result from the body mistaking its own tissues for foreign invaders and attacking them. And inflammation, which helps in cases of infection, can persist in the body chronically, a phenomenon that has increasingly been linked to diseases such as diabetes, heart disease, obesity, and Alzheimer's disease.
So good immune health means doing battle with the bad guys, but also knowing when to fight and when to back down. When something goes wrong with the immune system, says Stram, "what the body wants to do is regain balance." This gets more challenging as we age, since the older we get, the more immune cells we lose (that's why older people tend to be more susceptible to infections, and possibly cancer). But even among otherwise healthy young adults, lifestyle choices can tip the scales toward illness or health.
The Stress Connection
An entire field of research called psychoneuroimmunology has bloomed in recent years. It aims to uncover the links between the brain, behavior, and the immune system. One of its primary targets is the universal phenomenon known as stress.
We've all experienced the nasty cold that comes after a deadline, and scientific evidence has borne out this pattern, with clinical studies showing that psychological stress can weaken defenses and slow recovery from illnesses small and large. A recent study from the University of California, Los Angeles, in fact, found that the effects of stress play out at the cellular level: Hormones cued by emotional stress make immune cells age faster.
What is stress? "It's our body's response to something that taxes or exceeds our resources, whether from external pressures or our own internal worries," says Frances Cohen, a psychologist at the University of California, San Francisco. What feels stressful depends on a person's reaction to a given circumstance. "For some people, getting divorced is a positive step," she says. "But for others, it's devastating." When we perceive something as harmful, our brain triggers hormones such as cortisol, which can affect the immune system. "You can trace it from the brain through the body," Cohen says.
After stress hormones pour into the bloodstream, "the body tries to correct itself, to bring itself back into homeostasis," she adds. So if the stress is brief, the hormones dissipate, and the body returns to normal. In one study, her group found that people who lost their jobs had lower levels of an important class of immune cell. However, she says, "we saw a recovery of immune levels, a bouncing back, in people who got a new job."
Stress that lasts over a long period of time proves far more damaging to our bodies than short-term stress. A study published earlier this year, for instance, found that consistently high levels of perceived stress could reduce women's ability to fight an infection from human papilloma virus (HPV), which can cause cervical cancer; no such effect occurred with one-time stressful events such as job loss.
And in a preliminary study published in August, researchers studied people caring for family members with chronic illnesses (a long-term stressor); compared with a control group, the caregivers' white blood cells were less responsive to cortisol and more responsive to a pro-inflammatory compound -- leaving their bodies in a state of chronic inflammation.
Exercise and Sleep
Immunity isn't all in your head, of course; day-to-day physical habits matter a great deal. Exercise, sleep, and nutrition in particular have strong links to immunity -- and, not coincidentally, to our mental well-being.
Start with fitness: Those who exercise regularly, says Monika Fleshner, Ph.D., a professor of integrative physiology at the University of Colorado at Boulder, acquire a resiliency that makes them less susceptible to health problems. "This is especially important when we're stressed and as we age," says Fleshner.
Interestingly, more exercise isn't necessarily better. "While too little exercise is bad for the immune system, too much is just as bad," she notes. Athletes who exercise strenuously may have higher rates of respiratory infections. Just the right amount of movement helps maintain a healthy weight, which in turn plays a role in how well we battle colds and flus: People who are obese have diminished immune responses and more severe infections.
The fact that many Americans don't get enough sleep and rest spells bad news for our immune systems, too, says Motivala, increasing the risk of conditions ranging from frequent colds to diabetes. "A normal sleep cycle is vitally important for immune function," he explains, since immune cells circulate throughout the body according to cycles of sleep and wakefulness. Their levels in the blood peak around midnight, then gradually return to lymph nodes as we sleep. A lack of sleep interrupts this process, lowering levels of "natural killer" cells, important first-line defenders against infections.
No discussion of colds and flus would be complete without a mention of the food factor. "Nutrition plays a very important role in regulating the immune response," says Simin Nikbin Meydani, director of the Nutritional Immunology Laboratory at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University.
Clearly, poorly nourished people, particularly those in developing countries, are more susceptible to infections. But even people in wealthier countries, Meydani says, can have diets that lack certain nutrients. When deprived of any of the good-health essentials -- vitamins, minerals, healthy fats, protein -- the immune system can suffer.
Antioxidants such as selenium, beta-carotene, and vitamins A, C, and E seem especially critical for immunity; studies have found that diets lacking selenium, for instance, allow viruses to mutate more quickly, making them more dangerous. Some research shows that diets rich in antioxidants from fruits and vegetables, beans, and nuts may benefit the immune system. Green tea, with its potent antioxidants, stands out on the beverage front, while immunity-boosting seasonings like garlic, onion, oregano, cumin, and cinnamon contain natural antibacterial compounds that can help prevent infections.
On the flip side, some types of food actually chip away at our ability to fight infection -- in particular, refined sugar, which can significantly dampen immune system function. Trans fats, found in many processed foods, have been shown to promote inflammation.
Like the immune system itself, many of these health-friendly habits are highly intertwined. Lowering stress levels helps you sleep more soundly and makes you more likely to choose nutritious foods; exercise helps reduce stress and improve sleep; sleeping well gives you the energy to exercise. By developing good habits for both our minds and our bodies, says Stram, "we can significantly affect our health and well-being and improve our immunity."
Optimize Your Immunity
Strengthen your body's defenses against illness with these steps.
Manage Your Stress
You can't control everything in your life -- a job loss, a loved one's death, a personal setback -- but you can change how you react to unpleasant events. "How you cope with stressful situations can reduce the negative effects," says psychologist Frances Cohen.
Relieve tension through methods such as meditation, yoga, or tai chi -- all shown in studies to bolster immunity. Whatever you choose, practice it regularly. Integrative physician Ronald Stram, M.D., suggests meditating for a half-hour a day or practicing yoga three to four times per week to lower stress and improve quality of life, as well as boost the immune system.
If you find yourself feeling overwhelmed, try to step back and view the problem from a larger perspective, suggests Cohen. We tend to feel stressed when we think we're unable to cope. Build your resources by seeking friends, support groups, or information.
Without a nourishing diet, your body is more vulnerable to infections. Tieraona Low Dog, M.D., director of the Fellowship at the Arizona Center for Integrative Medicine at the University of Arizona, suggests aiming for a 70 percent plant-based diet that emphasizes fruits and vegetables, whole grains, seeds, and nuts. Include protein-rich foods low in saturated fat, such as beans and low-mercury fish such as wild salmon, anchovies, and herring. During cold and flu season, reach for dark fruits and berries, particularly blueberries and raspberries, which seem to have immunity-boosting effects. Use garlic, onion, ginger, and spices liberally in cooking.
Move for 30 Minutes Daily
Getting regular exercise helps your body avoid succumbing to illness in times of stress. But since too much exercise may lower immunity, aim for a happy medium. Integrative-physiology professor Monika Fleshner suggests getting 30 minutes of daily physical activity: Try biking, walking, and even gardening or cleaning. If you're an athlete, take extra care to eat a nourishing diet (including plenty of slow-burning carbohydrates, protein, fruits, and vegetables).
Go for Good Bugs
Food and supplements that contain helpful bacteria, known as probiotics, promote digestive health and have been linked to stronger immunity. For everyday health, eat yogurt with active cultures several times weekly; if you can't tolerate dairy, try miso soup or sauerkraut. During the cold and flu season, consider adding a supplement (which has at least 10 times the amount of good bacteria as yogurt) to your prevention routine. Stram recommends taking a supplement with Lactobacillus GG, Lactobacillus acidophilus, and Bifidobacterium, and aiming for 10 billion units of bacteria daily for prevention or up to 20 to 40 billion units during an illness.
Choose Supplements Wisely
Though most of us can benefit from a multivitamin, says Low Dog, we don't need other dietary supplements for immune support. But if you tend to get a lot of colds and flus, try taking the herb astragalus during winter months. Twice a week, suggests Low Dog, add 1 to 2 slices of dried astragalus (available at jeansgreens.com or Frontier co-op) to a pot of soup and cook for 20 to 30 minutes. Remove the astragalus and eat the soup. Alternatively, take 1,000 mg of astragalus extract daily.
Evidence shows that sleep has wide-ranging effects on immunity. Most of us need about eight hours a night, but quality matters just as much. "Keep track of how you feel in the morning," says Sarosh Motivala. A little grogginess is fine, but you shouldn't be dragging. "If you're waking up tired, it doesn't matter if you had eight hours or five hours, something is not right," he says. Sleep problems can arise from a number of sources, including stress, a poor diet, or a sedentary lifestyle, so talk to your doctor to identify the cause in each case.
Getting Over an Illness
It's not always possible to avoid colds and flus, says Low Dog. But when you do get sick, you can help your immune system conquer the infection and get back on track. Remember that "nothing works well if you don't start it in the first 24 hours," she says.
Pop Some C
While not necessarily a preventive measure, vitamin C does appear to reduce cold symptoms. It quickly gets flushed out of the system, says Low Dog, so take 500 mg three or four times a day at the beginning of a cold.
Low Dog recommends 1,000 mg of echinacea three to five times a day. Another herb, andrographis, has rendered colds less severe in controlled clinical trials. A combination of eleuthero and andrographis, sold under the name Kan Jang, was also found to reduce symptoms of respiratory infections. Follow the package directions.
Be a Patient Patient
"You need to take time to convalesce and get better," she says, or you risk experiencing symptoms that drag on and on. Follow your instincts for getting extra rest, and you'll get back on your feet much sooner.
Fortify Your System
Western medicine can learn from the Eastern concept of tonification -- the idea that we need to strengthen the body, particularly after an illness, says Low Dog. In addition to sleep, hydration, and good nutrition, she recommends considering Panax ginseng, at 200 mg daily.