3. Buy Supplements
Certain natural remedies can help you stay healthy this winter. Here's what might work best for you.
If you don't like fish...try omega-3 fatty acids. Get the same protection with a daily dose of purified fish oil capsules containing at least 1 g combined of EPA and DHA.
If you don't get enough sunlight...try vitamin D. People who took 2,000 IU of vitamin D daily had 70 percent fewer colds and flu than those taking a placebo, according to a three-year study published in Epidemiology and Infection. Even with fortified foods, most people don't get enough D, which the body produces when sunlight hits the skin. The amount used in the study exceeds the DV; Somer recommends not exceeding 1,000 IU a day.
If you feel a cold coming on...try Cold-fX. Subjects who took two daily capsules of Cold-fX (available online), a supplement containing North American ginseng extract, caught half as many colds as a group taking a placebo, according to a study done by the Center for Immunotherapy of Cancer and Infectious Diseases at the University of Connecticut. When they did get sick, their symptoms lasted less than half as long. This particular ginseng variety contains compounds that increase white blood cells and interleukins, proteins the immune system relies on.
More: Foods That Prevent Winter Colds
If you feel a cold coming on... try zinc. The research on this mineral has been conflicting. Still, "30 mg taken at the very start of a cold will shorten it by about half a day," says David L. Katz, MD, MPH, director of the Yale University Prevention Research Center. But don't overdo it. While even a slight deficiency in zinc, which is needed to produce white blood cells, can increase your risk of infection, more than 50 mg daily can suppress your immune system and block absorption of other essential minerals.
All your influenza questions answered here by the doctors.
4. Play Hard--Then Get Some Rest
Exercise and sleep are powerful natural immunity boosters. Here's how to get the right amount of both.
Get moving. Moderate exercise—around 20 to 30 minutes a day—increases blood flow, speeding nutrients to your cells, and decreases stress hormones, which dampen immune response, says Katz. And according to a study published in Medicine & Science in Sports & Exercise, regular physical activity—as long as it's not extreme—lowers your overall risk of upper-respiratory infections.
Snooze for at least seven hours a night. "A single night of sleep deprivation can depress your immune system," says Katz. After 153 healthy men and women were exposed to a cold virus, those who had slept more than seven hours each night during the preceding 14 days reduced their risk of contracting the rhinovirus by up to 300 percent, according to a study published in Archives of Internal Medicine. And get some solid shut-eye the night before your shot. According to research published in the Journal of the American Medical Association, when healthy men were limited to four hours of sleep before getting a vaccination, they developed only half the normal number of antibodies.
Try tai chi. When women ages 55 to 65 practiced tai chi for an hour four times a week, Shanghai University of Sport researchers saw the women's levels of two different disease-fighting cells jump by nearly 32% over 4 months. Start practicing a week before your flu shot and you can boost its effectiveness by as much as 17 percent, found a University of Illinois study. To get started, try Element Tai Chi for Beginners ($15; collagevideo.com).
Party on—moderately. People who are socially active get fewer colds, even when intentionally exposed to the cold virus. Researchers postulate that frequent socializers tend to be more positive and maintain high-quality emotional ties, both of which strengthen immunity.
The top 10 worst things for your immune system.
More: 3 Foods to Treat Your Winter Cold
3 Supplements You Can Skip
Many people waste money on preventive measures that are all hype. Here are three of the most egregious:
A 2007 review of 30 studies found no evidence that vitamin C prevents colds in the normal population. Possible side effects: Megadoses can cause kidney stones, upset stomach and even internal bleeding in children.
If taken at the start of a cold, it might shorten duration and severity. But some brands do not contain the amount of echinacea listed on the label—and some formulas have none at all. Possible side effects: Allergic reactions may include wheezing, rash, and diarrhea.
Experts say this supplement does nothing to repel germs on an airplane or anywhere else. Possible side effects: It contains large amounts of vitamin A, which could be toxic if taken several times a day.
More: 6 Green Super Foods to Add to Your Diet
Put your immunity to the test at a fitness class.