Working out may be critical to helping you lose fat and putting on muscle, but the act of exercising has a sneaky downside: It releases free radicals, oxygen molecule byproducts that lead to aging and diseases such as diabetes and cancer. That doesn't mean you need to stage a permanent gym walkout. By eating the right kinds of foods, such as the leafy green known as watercress, you can minimize much of the damage to your DNA triggered by free radicals during high intensity exercise, according to a recent study from the British Journal of Nutrition. People were asked to consume 85 grams of watercress—that's approximately one small bag—each day for eight weeks. Afterward, they were asked to participate in high-intensity treadmill exercise. The researchers found that the group that ate the green veggie had less DNA damage than those who didn't have any. The experts also found that its didn't really make a difference if you eat watercress daily, or every once in a while—people who munched on the green two hours prior to working out got the same level of protection as those who had been eating it for weeks on end. To protect yourself (and your all-important DNA) start incorporating the peppery-tasting leaf into your salads, or blend it into vegetable smoothies.