WORK OUT, BUT DON'T OVER WORK
During very intense exercise, the body handles the physical stress in part by pumping out the emergency hormones cortisol and adrenaline. The hormones tem porarily impair immune function, which may allow viruses and bacteria to gain a foothold during those periods. That may explain why several studies have found increased susceptibility to infection among people who exercise extremely hard-while preparing for a marathon, for example. Workouts that aren't exhausting, however, have the opposite effect:
They temporarily strengthen the immune system, by boosting the aggressiveness of natural killer cells and the bacteria-gobbling capacity of other immune cells called macrophages. Repeated often enough, those short-term boosts, lasting up to a few hours, can apparently yield substantial benefits. Researchers at the University of South Carolina and the University of Massachusetts recently studied some 550 adults.
Those who regularly exercised at least moderately had about 25 percent fewer colds during the one-year study than those who seldom or never exercised. Results of at least three small clinical trials tend to other ways, too: It contributes to weight gain and diabetes by disrupting hormone levels, and it diminishes mental and physical performance.
Recommendation: Most people need seven to eight hours of sleep a night. If you sleep less than that or are often tired during the day, try to change your sleep habits. Effective strategies include establishing a regular sleep and rising time, avoiding naps, blocking out disturbances, reserving your bed only for sleep and sex, and limiting your liquid intake-especially of beverages that contain caffeine or alcohol-for a few hours before bed. If you don't drift off to sleep within about 30 minutes, or wake up and can't fall back asleep, get up and do something quiet until you feel drowsy.
1) Avoid excessive sun exposure. While the body needs some sunlight to produce vitamin D, too much sunshine can suppress the immune system. Overexposed skin is susceptible not only to skin cancer but also to infections, possibly because of impaired immune responses, both systemically and within the skin itself.
Recommendation: If you expect to spend more than about 20 minutes out in the sun from mid-morning to late afternoon during the warmer months in the North or year-round in the South, wear sun-protective clothing and sunglasses, and slather on sunscreen with a sun protective factor (SPF) of at least 15.
2) Limit exposure to pesticides and mercury. Animal and lab research suggests that those substances, especially in high doses or with extended exposure, may degrade immune function. A few observational studies have found that people who often work with mercury or ce rtain pesticides may have weakened defenses.
Recommendation: To reduce exposure to pesticides, (thoroughly wash fruits and vegetables under running water; use a soft brush and a diluted solution of dish soap to scrub apples, bell peppers, tomat oes, and other produce coated in pesticide-trapping wa x. Consider buying organic p roduce when it's available and affordable. To minimize ex posure to mercury, limit yo ur intake of fish that may be h igh in the metal, such as king mackerel, shark, swordfish, and to a lesser extent, fresh-water bass, halibut, and canned white tuna.
3) Limit antibiotic use. Recent studies suggest that exposure to infection and other allergens early in life may help build a well-developed immune system. Conversely, frequent exposure to antibiotics may weaken immunity by killing the bacteria that the body would otherwise have to grapple with and that would ultimately strengthen it.
Recommendation: Don't use antibiotics to treat viral infections, such as the common cold. (The drugs won't harm the virus, but they will kill lots of the helpful bacteria that live of the helpful bacteria that live in the body. And needless use helps breed antibiotic resistance.) Parents should also refuse antibiotic treatment for fluid buildup in their children's ears unless an examination clearly shows an infection.