By Steve Edwards

Could doing INSANITY® or P90X® increase your risk of getting sick? Two recent studies have led several publications to state that intense exercise should come with a warning that it increases the risk of illness. Today we'll take a deeper look at these claims, analyze what they mean for you, and look at a few ways to keep your immune system strong.

To someone who's been involved in athletic training their entire life, the studies look like a bunch of hoo-hah from the "duh" files. But for the general public, they've created quite a stir, leading many authors to pen articles warning about the dangers of hard exercise. Great, I'm thinking, just what our swelling society needs—another excuse not to exercise. Some of these articles were so craftily written, I even got a note from Tony Horton asking for my take. So obviously, the media fright club did its homework on this one.

Here's the rub. Two independent studies found that while moderate exercise boosted your immune system, intense exercise broke it down. The media spun this to challenge the notion that hard exercise is good for you, stating we should consider only recommending moderate exercise. The problem with that assessment is that to improve your fitness, you must continually stress your system, a process known as progressive overload in training circles. Over time, progressive overload leads to improvements in your immune system. Without it, your fitness will stagnate and your immune system will regress.

This doesn't mean these studies were without merit. As your training load increases, so does the demand on your immune system, because exercise creates stress on the body. It's the classic what-doesn't-kill-you-makes-you-stronger scenario. Intense exercise increases the amount of hormones your body releases. These hormones are essential for all bodily functions. During the acute phase of intense exercise, however, these hormones are busy trying to repair all the physiological breakdown your workout incurs on your body, and there isn't enough left to boost your immune system. Therefore, during times of high stress, your immune system is compromised.

The upside is that your body gets used to this process. As your body grows accustomed, less physiological breakdown occurs during the same high-intensity movements, but the hormonal releases are still active. These hormonal releases increase the body's natural defenses—your immune system. So intense exercise leads to an improved immune system provided you survive the initial stages of your program.

And despite all the hoo-hah, it isn't hard to improve your immune system. It should seem obvious that the harder you exercise, the healthier the rest of your lifestyle should become; but that doesn't create the controversy the media covets. With this in mind, let's look at ways to boost your immune system during times of stress.

Behavioral Changes
  1. Get plenty of sleep. Sleep is vital for everything you do and especially for you to recover from exercise. When you don't get enough, the first thing to fail is your ability to fight off illness. Pathogens exist in all walks of life, and fighting them off is an essential part of your well-being. A rested body is a recovered body, and when your body is strong, it's more efficient.
  2. Avoid outside stress. During times of intense training, it's wise to do your best to avoid as much outside distraction as possible. I try to schedule my hardest training phases during when I don't have a lot of commitments. When I have a big travel schedule or a massive workload on the horizon, I try scaling back my exercise accordingly.
  3. Wash your hands. A very simple act that's highly effective when it comes to keeping you healthy. You don't need fancy antibacterial soap. Any simple soap will do. Just wash your hands often because most of the things you touch, especially in public, are covered in germs. To make this easier, you can buy waterless hand sanitizers, which were popularized by travelers in countries where the water was unsafe.
  4. Avoid enclosed spaces for long periods of time. This one's tough, since most of us work or go to school in enclosed spaces. But just because you're forced into a space doesn't mean there's nothing you can do about it. We could all benefit from taking more breaks. Our bodies and our minds will perform better if we give them a break every hour or so. This is why classes tend to be about an hour long. Moving outside of your enclosed space helps you recharge with clean air, sunshine, and vitamin D.
  5. Don't skip your recovery periods. There's a reason INSANITY and P90X have recovery weeks built into their schedules. Intense training should only be done in short cycles. One of the most common ways people get sick or injured is by trying to prolong the amount of time during which they Bring It. As good as it feels to keep pushing yourself to your limit, you have a breaking point.
Diet Changes

Following a healthy diet enhances each behavioral change mentioned and everything else you do in life. Staying hydrated, in particular, is also very important for your immune system. Supplementing during times of high stress, and when you're forced to stay in an enclosed place for long periods of time (like in an airplane), has been shown to reduce your chances of getting sick. But these are all obvious things, right?

What's less obvious is that many natural foods and herbs have been shown to improve the immune system. None of these are "proven" medical remedies, but they all have a long history of anecdotal lore that probably has some relevant meaning, even if the American Medical Association hasn't blessed them in the same way it has pseudoephedrine. Whether they work or not, all these foods have healthy benefits to supplement your diet, so file them under the "why not" category. With that disclaimer, here are 10 foods that may boost your immune system.
  1. Garlic. From staving off vampires to having antiviral and antibacterial properties, garlic has been a wonder food of holistic medicine for as long as we've been writing about it. Just eat it in its natural form—there's a reason you've never seen anyone defend themselves against Dracula with garlic salt.
  2. Citrus fruits. They're not just for scurvy anymore. Citrus fruits are all high in vitamin C—the vitamin most commonly associated with a strong immune system.
  3. Echinacea. Another one long on lore but short on science, its anecdotal history in antiviral medicine shouldn't be discounted. However, this herb is best used only in times of severe stress.
  4. Berries. These fruits contain exceedingly high amounts of antioxidants, which are directly responsible for fighting off would-be illnesses.
  5. Zinc. Not a real food, but with the popularity of zinc lozenges, who would know? There's good science behind zinc supplementation, but again, it's a high-stress supplement only. Don't make sucking on these a part of your daily diet.
  6. Oysters. For those who want to take their zinc naturally, nothing beats oysters. And to think that all this time we've only thought of them as aphrodisiacs.
  7. Shiitake mushrooms. Long used in Japan for their antibacterial and antiviral qualities, we're lucky they're now common ingredients in haute cuisine.
  8. Yogurt. One of the few foods that's been a cornerstone of an entire region's diet, as it was for most everyone living between Eastern Europe and Central Asia for about 4,000 years. The bacteria in yogurt helps us digest other foods better, as well as helping us fight off many dangerous bacteria.
  9. Carrots. High glycemic index be damned. There's no negative research—and plenty of positive research—associated with eating carrots. They're exceptionally high in beta-carotene, and in a study on children's school attendance, beta-carotene was found to improve cognitive function and attendance in the participants.
  10. Astragalus root. Another popular herb used in traditional Chinese medicine that's picking up steam under the scrutiny of Western science. Unfortunately, the only downside is that it's not yet found its place in haute cuisine—although it can be found in Beachbody's Herbal Immune Boost.