I’m just getting over a spring sinus infections. Again! I’ve always considered myself a middle-of-the road, moderate intensity runner. I run two marathons a year and dabble in triathlon in the spring and summer. Nothing crazy. Yet, every spring I seem to be susceptible to the dreaded runny nose syndromes. I’ve always chalked the whole thing up to Texas allergens, but is that it? Or does my running make me more susceptible to the common cold? Interesting question posed to me by an ENT colleague. She pointed out that many marathoners experience significant increase in upper respiratory infections in the post-race months.

Let’s look at the research. A recent survey of 30 different studies of runners and decreased immune function that may lead to increased upper respiratory infections revealed little agreement from the experts. Yes, they all agree that moderate activity may enhance immune function, but they describe this as brisk walking for 30 to 45 minutes a day. What runner does that little activity? Most studies also agreed that high-intensity exercise temporarily impairs the immune competence. Hence the increased incidence of upper respiratory infections in marathon runner and especially ultra-marathon runners.

Athletes, when compared with their couch potato colleagues, experience higher rate of upper respiratory infections especially in the few weeks after intense training and races. In non-athletes, increasing physical activity is associated with a decreased risk of upper respiratory infections.

This so-called open window of altered immunity is temporary, lasting from three to 72 hours after an intense, prolonged event. Nevertheless, it presents an ideal opportunity to viruses and other invading pathogens, especially those that enter the body through the respiratory system.

Sounds bad, so what can we do to increase our immunity and avoid the runny-nose syndromes?

Several vitamins and minerals, including vitamins A, E, and C, and the minerals zinc and iron, are essential for normal immune function. Vitamins C and E, in particular, are also powerful antioxidants. It has long been known that long-distance running and other endurance events can increase the levels of free radicals—molecules that oxidize and cause damage to cells, including immune cells. The body produces its own antioxidants to counter free radicals and oxidative stress.

Many runners, operating under the theory that more of a good thing is better, take vitamin and mineral supplements. And while moderate amounts may very well be beneficial for the active individual, there is little evidence to support taking megadoses, with the possible exception of vitamin C. Some studies found that taking vitamin C (about 600 milligrams/day) for three weeks before an ultramarathon reduced postrace cold symptoms. Other researchers have found that vitamin C supplementation made no difference. Sounds like a multivitamin with extra vitamin C can’t hurt, but may not be our savior!

Should you run when you’re sick?

If you have a cold, most doctors recommend waiting a day or so after your cold symptoms disappear to resume intensive exercise. Mild to moderate exercise (such as walking) when you have a cold is fine. If your illness is more serious—fever, fatigue, muscle aches—you should wait two to four weeks before resuming your training regimen. Like any of us do that!

Just as intense, extended physical stress can depress certain immune responses, so too can chronic psychological stress and inadequate sleep. So during periods of intense training and before long races, the take-home message is this: keep other life stresses to a minimum if possible. Get enough sleep, avoid rapid weight loss, and eat a healthy diet. Sounds like a no-brainer!

Bottom line: marathon runners are more susceptible to upper respiratory infections. Getting more sleep, decreasing your overall stress and taking a multivitamin with extra vitamin C may help.