6. Not getting enough vitamin D
We get vitamin D from the sun, but in many parts of America during the winter you won’t be able to pick up enough vitamin D to maintain healthy levels, no matter how much you go outside. And low vitamin D has been shown to impact our immune systems and make us susceptible to colds. “There’s evidence that people who live in nursing homes givien vitamin D are less susceptible to flu outbreaks,” says Dr. Borins. Adults should take 400 to 1,000 IU a day in a supplement pill or drops to impact health overall, including your bones, long-term risk for serious illnesses such as cancer, and short-term health of your immune system to fend off colds and flues. If you head south every winter, that’s great for your vitamin D levels – but you may still need a supplement, too.