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.
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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."