Getting plenty of this vitamin may strengthen your immune system and make venturing out of your house a little less scary this flu season. We’re talking about the sunshine vitamin — good old D.

In a study done during flu season, people who had higher blood levels of vitamin D were half as likely to get hit with the bug — or any other viral infection of the respiratory tract, for that matter.

“D” Is for Defense
Not only were the D lovers in the study less likely to get sick compared with people who had lower D levels, but the high-D group also tended to be out of commission for fewer days when they did get hit. Of course, washing your hands frequently and living a healthy lifestyle are still the cornerstones of flu avoidance. But it’s nice to know that a D supplement could act as positive reinforcement. Researchers aren’t totally sure why D helps, but it could be that this immune system vitamin’s inflammation-suppressing powers help reduce the severity of infections.

Another good defense against flu? Getting vaccinated.