The Latest Cold + Flu Fighter

Although past studies have indicated that endurance sports (like that marathon training you’re pondering) put strain on the immune system, a new analysis in Frontiers in Immunology is flipping the script. We know that during intense exercise, infection-fighting immune cells increase 10 fold in the bloodstream, drop to low levels afterward and finally return to normal hours later—a finding that was previously interpreted as a sign of immune suppression. But now researchers speculate that this cell-turnover timeline is impossible, meaning that the “destroyed” cells (that were thought to have regenerated just hours later) can’t be replaced that quickly. Moreover, these “lost” cells actually end up in other more infection-prone parts of the body like the lungs. So it turns out that all exercise, and that includes the intense stuff, is good for immunity. One last thing, though: Make sure you’re balancing your marathon-training schedule with plenty of low impact, flexibility exercises like Pilates or yoga.

—Amanda Altman