Nov. 26, 2012 -- With flu season upon us, there's never been a better time to get the flu shot and take some other easy steps to boost your immunity.
Flu kills as many as 49,000 Americans every year and leaves more than 200,000 hospitalized with complications like pneumonia, according to the U.S. Centers for Disease Control and Prevention. Most vulnerable are the elderly or chronically ill, whose immune systems have been worn down, and infants, whose immune systems haven't yet been built up.
Seasonal influenza viruses may change their genetic structure from year to year, but the basic strategy for surviving them doesn't, starting with the flu vaccine that U.S. health officials recommend for everyone older than 6 months. From there, though, flu avoidance involves committing to a range of mostly simple steps.
The Sunny Solution
Emerging science about the disease-defeating effects of vitamin D, which we obtain either from sunshine or supplements, suggests that it can create a protective internal barrier between our cells and flu viruses. Most of the evidence remains suggestive, based on what happens in test-tubes or animals. However, a study of Japanese school children published last year has given vitamin D advocates something concrete to hang onto. Researchers divided 334 children into two groups, giving half daily pills containing 1,200 international units of vitamin D and the other half dummy pills. Among the 167 given real vitamin D, 18 (10.8 percent) caught the flu, compared with 31 (18.6 percent) of the 167 who got placebos, acording to the study in the American Journal of Clinical Nutrition.
Vitamin D activates proteins in the body's innate immune system, the first line of defense drafted into duty in the presence of disease-causing invaders, according to Adrian Gombart, whose research focuses on how the so-called sunshine vitamin keeps infections at bay.
"There's a lot of evidence from research in the lab that there may be a reason to believe vitamin D could help fight off flu infection," Gombart, an associate professor at Oregon State University's Linus Pauling Institute, said in an interview. In the last few years, scientists have determined that in humans and in apes, vitamin D turns on the production of a protein called cathlecidin antimicrobial peptide, which as its name suggests, kills bacteria and viruses. It may be particularly effective in the lungs, Gombart said.
Click here to see some immunity-boosting foods.
In the absence of research establishing what dose of vitamin D is likely to protect against the flu, healthy people should consider The Linus Pauling Institute's general recommendations for vitamin D: 2,000 IU daily for healthy adults and 600 IU a day for children. Even with individual variations in how people's bodies respond to vitamin D supplementation, those doses should create sufficient vitamin D levels in the bloodstream, he said.
"I would think of it this way: If you have sufficient vitamin D, you're going to have an optimal immune response," Gombart said. "That may reduce rates of infection. It also may reduce the severity of the infection. Individuals may be sick, but maybe not as severely. Or may just not get sick. We can't really say at this point."
Keep Your Immune System Tuned Up
Sufficient sleep, regular exercise and eating healthfully can keep your immune system in good working order and ready to stand up to flu. Research continues to suggest that keeping a lid on stress is essential for a healthy immune system. That's because chronic stress triggers excess production of cortisol, a hormone that suppresses important infection-fighting cells. Consider setting aside 30 minutes each day to listen to soothing, environmental music, which ups the production of immunoglobulin A (IgA) proteins, according to a study that found listening to a half-hour of relaxing music boosted IgA levels in study subjects' saliva.
Regular, "moderately frequent" sex also raises IgA levels, according to researchers who found that sex two to three times a week made for higher IgA levels than either abstinence or more frequent sex. IgA proteins cling to infection-causing microbes and recruit immune cells to battle them. Massage and therapeutic touch also reduce cortisol levels while increasing the population of natural killer cells and infection-fighting white blood cells, according to a 2004 study from the Touch Institutes at the University of Miami School of Medicine.
Ease Up On Nose-blowing
Blowing your nose hard increases pressure in your sinuses, forcing germ-laden mucus further into your nasal passages, according to University of Virginia researchers who used CT scans to track what happened when study subjects blew their noses, sneezed and coughed. Driving viruses deeper into your sinuses can prolong your misery, Schaffner says. Consider loosening nasal secretions with a hot, steamy shower, thenyou can blow your nose with less risk.
Click here to see eight flu-fighting gadgets.
The Last Resort: Antiviral Drugs
If all else has failed and you feel the flu coming on, call your doctor and ask about a prescription for one of the antiviral drugs, such as oseltamivir (Tamiflu) or zanamivir (Relenza). These can "lessen symptoms and shorten the time you are sick by 1 or 2 days," according to the federal Centers for Disease Control and Prevention. "For people with a high-risk medical condition, treatment with an antiviral drug can mean the difference between having a milder illness versus a very serious illness that could result in a hospital stay." Of course, you might want to keep in mind that in rare cases, these medications can make you feel as bad as the flu itself, producing such unpleasant side effects as nausea, vomiting, dizziness, diarrhea, headache or mood changes.
A version of this story previously appeared on ABCNews.com.