It's the time of year when runners tolerate more than just cold temperatures, biting winds, and slick roads. When we venture out for our daily ritual, we face the tsk-tsking of nonrunning spouses, coworkers, and snowplow drivers who think we're nutcases just asking for bronchitis or the flu.
Little do they know that running--even in frosty conditions--strengthens not just our hearts and quadriceps but also our lymphocytes and neutrophils. These immune cells protect us against attack from bacteria and viruses that cause illness and infection. Indeed, a study from the University of South Carolina reported that people who exercise have 20 percent fewer colds than their sedentary counterparts.
There's a catch, however. Most data cite immune boosts after 30 to 75 minutes of moderate activity. Runners doing longer or more intense workouts (listen up, Boston qualifiers) don't usually see this benefit. In fact, a large body of research, mostly from Appalachian State University in Boone, North Carolina, indicates that a strenuous workout or prolonged periods of heavy training can have the opposite effect. "When you're running for 90 minutes or longer, there's a temporary downturn in immunity," says David Nieman, Dr.P.H., director of the Human Performance Laboratory at Appalachian State. The lead author of the majority of the research, Nieman is a veteran of 58 marathons. Around the 90-minute mark, he says, carbohydrate stores drop, causing a spike in two key hormones, cortisol and epinephrine. This, in turn, inhibits those neutrophils and lymphocytes, leaving you vulnerable to nasty bugs.
The good news is that sneezing and fevers aren't inevitable, and you don't have to give up your training to stay healthy.
Viruses have a greater chance to get a foothold during the "open window" of impaired immunity--three to 72 hours after a workout. Experts say one way to prevent this dip is to drink carbohydrate-rich beverages before, during, and after your run. This is key even in the winter, when runners tend to sweat less and cut back on fluid intake. In his pioneering 1998 research, Nieman found that consuming sports drinks keeps carbohydrate stores high, slowing the rise of stress hormones and offsetting negative immune responses. On the day of a workout that exceeds 90 minutes, Nieman recommends drinking 16 ounces of a beverage containing 60 grams of carbohydrate (the amount in most sports drinks) 30 minutes before you start. During the run, drink an additional 16 ounces every 30 minutes. Then, after your workout, drink another 16 ounces. Nieman says fluids are the fastest delivery system for carbs. So if you substitute your postrun drink with a banana or bagel, wash it down with water.
During the hours following a hard workout, be extra diligent about washing your hands regularly, avoiding crowded, germ-filled places, and getting to bed on time--if not early.
Throughout your training, you'll want to avoid increasing both intensity and volume at the same time. Raise your mileage, and then hold it at that level for a week or two before adding in tempo workouts. "Not only will this stair-stepped approach benefit your immune system, it may also make training more effective because the body can better adapt and recover from each session," says Brian McFarlin, Ph.D., an assistant professor in exercise physiology and nutrition at the laboratory of integrated physiology at the University of Houston. He also stresses the importance of tapering your training before a race to allow your immune system to fully recover. "If you force the body to choose between repairing muscle-tissue damage or fighting an infection, it's probably going to dedicate more resources toward the former," McFarlin says.
Carbs alone can't prevent colds, but Nieman predicts that within a year or two, a new wave of supplemented sports drinks will help bolster your defenses. Quercetin, an antioxidant derived from black tea, apples, berries, and other foods, is one of the most promising ingredients. Research indicates that athletes who take 1,000 milligrams of quercetin for three weeks before, during, and two weeks after a three-day period of intense exercise have fewer upper-respiratory-tract infections during the two weeks after the workouts. But Nieman warns that studies to determine the long-term effects of quercetin are still ongoing. Beta-glucans, a soluble fiber found in oats and barley, and curcumin, an anti?oxidant in turmeric, are two others to keep tabs on. So far, research has focused on superhigh doses--so you won't get the same benefit by simply eating a bowl of oatmeal for breakfast or sprinkling turmeric on your supper.
For now, researchers seem to know what doesn't work: Loading up on megadoses of supplements. Studies of zinc and glutamine show they do little to boost immunity or relieve postrace cold symptoms. Other supplements may do more harm than good. In 2004, Nieman found that athletes who took vitamin E leading up to the Ironman World Championship had greater oxidative stress and inflammatory responses than athletes who didn't use the supplement.
Bundling up against the cold or rushing to strip off your damp workout gear isn't likely to keep you from coming down with a cold or flu, either. "The idea that because you're cold, you're going to get sick is an old wives' tale," says McFarlin. Tell that to the doubters next time you're heading out on a winter run. Better yet, invite them along.