 Ultramarathon runners may generate so many free radicals during a race that they can damage the DNA of a significant percentage of their cells. Now some have looked on the exercise-induced increase in free radical production as a paradox. Why wouldn't apparently healthy act exercise lead to detrimental effects through damage to various molecules and tissues? This is somewhat of a misunderstanding, as exercise in and of itself is not necessarily the healthy act. It's the recovery after exercise that's so healthy. The whole, that which doesn't kill us, makes a stronger notion. For example, exercise training has been shown to enhance antioxidant defenses. For example, by increasing the activities of antioxidant enzymes. So, yeah, during the race, ultramarathoners may be taking hits through their DNA, but check out a week later. Six days after the race, they didn't just go back to the baseline level of DNA damage, they had significantly less, presumably because they had so revved up their antioxidant defenses. So maybe exercise-induced oxidative damage is beneficial, kind of like vaccination. By freaking out the body a little, maybe you'll induce a response that's favorable in the long run. This concept that low levels of a damaging entity can upregulate 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 then eating anti-inflammatory antioxidant-rich plant foods undermine this adaptation response? We saw that berries could reduce inflammatory muscle damage, and greens could reduce the free radical DNA damage. Dark chocolate and tomato juice may have similar effects. The flavonoid phytonutrients in fruits, vegetables, and beans appeared to inhibit the activity of xanthine oxidase, considered the main contributor of free radicals during exercise, and that carbs and 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. So if you decrease the free radical tissue damage, maybe you don't get that increase in activity of those antioxidant enzymes. The cherry researchers responded, look, although it's likely that muscle damage, inflammation, and oxidative stress are important factors in the adaptation process, minimizing these factors may improve recovery, so you can train more and perform better. So there's kind of theories on both sides, but what happens when you actually put it to the test? What does the data show? While antioxidant or anti-inflammatory supplements may prevent these adaptive events, researchers found that a very extract black current in this study, although packed with antioxidant and anti-inflammatory properties, actually augmented, boosted the health effects of regular exercise even further. But you take antioxidant pills, vitamin C and vitamin E supplements, and you can actually reduce the stress levels induced by exercise, but in doing so, you can block that boost in antioxidant enzyme activity caused by exercise. Now, maybe you don't need that boost if you don't have as much damage, but vitamin C supplements may impair physical performance in the first place. Whereas with plant foods, you appear to get the best of both worlds. Check out this recent study on lemon verbena, an antioxidant rich herbal tea, protects against oxidative damage, decreases the signs of muscular damage and inflammation, all without blocking the cellular adaptation to exercise. They 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. Here's 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 to that cause, the body started cranking up its antioxidant defenses. But give a dark green leafy tea, and not only do you put a kibosh on the damage due to all the phytonutrient antioxidants, you still get the boost in defenses. In fact, in this case, even better.