A “D”-fense against the Flu

If you’re dreading the approach of cold and flu season, you might want to boost your vitamin D. This micronutrient is known for its role in human bone growth, but a recent study suggests that it may also affect our susceptibility to wintertime illnesses.

Science is just beginning to understand exactly how vitamin D affects our immune system, but researchers have found that it plays two important roles: triggering disease-fighting T-cells, and protecting healthy tissues from being damaged in the healing process.

A recent study conducted by the University of California, Irvine, and the Mayo Clinic found that our vitamin D intake peaks in August and troughs in February—not surprising, since most of our D comes from exposure to the sun. But the study also found that as levels of the nutrient decline, our odds of contracting infections rise.

To balance out that seasonal decline, study coauthor Andrew Noymer of UC Irvine recommends increasing your intake with supplements (1,000 mg daily is fine), fortified foods, or foods that are naturally rich in vitamin D—such as oily fish, egg yolks, and mushrooms.

However, a lack of vitamin D isn’t the only reason for our inability to resist illness in the winter months. According to Noymer, “it’s a topic of current research why the cold and flu season is when it is. And the timing of the school year and the fact that people spend more time indoors is thought to play a role as well.”