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What Happens to Our Bodies After We Exercise & How to Boost the Health Benefits

We all know exercise is beneficial to our health. Then why is it that ultramarathon runners may generate so many free radicals during a race that they can damage the DNA of a significant percentage of their cells? Researchers have looked at the exercise-induced increase in free radical production as a paradox: why would an apparently healthy act—exercise—lead to detrimental effects through damage to various molecules and tissues? This arises out of somewhat of a misunderstanding: exercise in and of itself is not necessarily the healthy act—it’s the recovery after exercise that is so healthy, the whole “that-which-doesn’t-kill-us-makes-us-stronger” notion. For example, exercise training has been shown to enhance antioxidant defenses by increasing the activities of our antioxidant enzymes. So, during the race ultra-marathoners may be taking hits to their DNA, but a week later they may experience great benefits, as I show in the above video.

In a recent study, researchers from Oregon State University looked at the level of DNA damage in athletes. Six days after a race, athletes didn’t just go back to the baseline level of DNA damage, but had significantly less, presumably because they had revved up their antioxidant defenses. So, maybe exercise-induced oxidative damage is beneficial, similar to vaccination. By freaking out the body a little, we might induce a response that’s favorable in the long run.

This concept, that low levels of a damaging entity can up-regulate protective mechanisms, is known as hormesis. For example, herbicides kill plants, but in tiny doses may actually boost plant growth, presumably by stressing the plant into rallying its resources to successfully fight back.

Wait a second, though. Could eating anti-inflammatory and anti-oxidant rich plant foods undermine this adaptation response? We know that berries could reduce (See Reducing Muscle Soreness with Berries) inflammatory muscle damage, and greens could reduce (See Preventing Exercise Induced Oxidative Stress with Watercress) free radical DNA damage. Dark chocolate and tomato juice may have similar effects. The flavonoid phytonutrients in fruits, vegetables, and beans appear to inhibit the activity of xanthine oxidase, considered the main contributor of free radicals during exercise. And the carbs in plant foods may decrease stress hormone levels.

So in 1999, a theoretical concern was raised. Maybe all that free radical stress from exercise is a good thing, and increased consumption of some antioxidant nutrients might interfere with these necessary adaptive processes. If we decrease free radical tissue damage, maybe we won’t get that increase in activity of those antioxidant enzymes.

A group of researchers who performed a study on tart cherry juice and recovery following a marathon responded to this antioxidant concern by suggesting that, although it is likely that muscle damage, inflammation, and oxidative stress are important factors in the adaptation process, minimizing these factors may improve recovery so we can train more and perform better. So, there are theories on both sides, but what happens when we actually put it to the test?

While antioxidant or anti-inflammatory supplements may prevent these adaptive events, researchers found that blackcurrant extract – although packed with antioxidant and anti-inflammatory properties – actually boosted the health benefits of regular exercise.

If we take antioxidant pills—vitamin C and vitamin E supplements— we can also reduce the stress levels induced by exercise, but in doing so we block that boost in antioxidant enzyme activity caused by exercise. Now maybe we don’t need that boost if we don’t have as much damage, but vitamin C supplements seem to impair physical performance in the first place. With plant foods, though, we appear to get the best of both worlds.

For example, lemon verbena, an antioxidant-rich herbal tea, protects against oxidative damage and decreases the signs of muscular damage and inflammation, without blocking the cellular adaptation to exercise. In a recent study, researchers showed that lemon verbena does not affect the increase of the antioxidant enzyme response promoted by exercise. On the contrary: glutathione reductase activity was even higher in the lemon verbena group. If you click on the above video, you can see the level of antioxidant enzyme activity before and after 21 days of intense running exercises in the control group. With all that free radical damage, the body started cranking up its antioxidant defenses. But give a dark green leafy tea, and not only do we put a kabosh on the damage due to all the phytonutrients and antioxidants, but we still get the boost in defenses—in fact, in this case, the boost was even greater.

Find out more on enhancing athletic recovery in this three-part video series:

1. Reducing Muscle Fatigue with Citrus
2. Reducing Muscle Soreness with Berries
3. Preventing Exercise-Induced Oxidative Stress With Watercress

Then there’s my 15-video series on using nitrate-rich vegetables to boost athletic performance starting with Doping With Beet Juice and ending with So Should We Drink Beet Juice or Not?

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live year-in-review presentations Uprooting the Leading Causes of Death and More Than an Apple a Day.

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Read more: Health, Diet & Nutrition, Eating for Health, Fitness, General Health, Men's Health, Natural Remedies, Videos, Women's Health, , , ,

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Dr. Michael Greger

A founding member of the American College of Lifestyle Medicine, Michael Greger, M.D., is a physician, author, and internationally recognized speaker on nutrition, food safety, and public health issues. Currently Dr. Greger serves as the Director of Public Health and Animal Agriculture at The Humane Society of the United States. Hundreds of his nutrition videos are freely available at


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1:27AM PDT on Oct 17, 2014

Thank you!

6:38AM PDT on Mar 20, 2014

Thank you for sharing.

4:04AM PDT on Mar 17, 2014

Thank you :)

5:26AM PDT on Mar 14, 2014


5:25AM PDT on Mar 14, 2014


4:54PM PDT on Mar 13, 2014


4:28PM PDT on Mar 13, 2014


2:36AM PDT on Mar 13, 2014

Thank you :)

8:45PM PDT on Mar 12, 2014


1:47PM PDT on Mar 11, 2014

I an fairly new to running and still struggling with stamina and speed. I found this article useful but confess I don't quite understand all of it. Seems like we're dealing with a paradoxical phenomena. I have decided to keep consuming what I already do as it works well enough.

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