It happens while we sleep, while we work and while we play. Every day, our bodies quietly fight a battle against enemies that sneak into our bodies in ways we might not consider. Once inside, they do their worst, attacking us at the cellular level and contributing to everything from wrinkles to cancer.

"We are constantly exposed to environmental factors such as pollutants in the air, smoke, harmful substances in the food that we eat, too much sun-they all come into our body and want to do some damage," said Laura Sechrest, director of food and nutrition services at St. Mary's Hospital.

These harmful substances, Sechrest explains, contribute to the formation of free radicals.

"Every cell in our body needs oxygen, and when they burn that oxygen, there is a by-product formed called a free radical," she said. "They can be thought of as unstable molecules. That unstable molecule-which is missing one electron-is always looking for stability. So it steals from other body cells to stabilize itself, and that's where the damage to those cells comes into play."

These damaged cells can lead to a host of diseases and ailments, including heart disease, diabetes, Alzheimer's, cataracts and cancer. Other damage caused by free radicals is simply part of the natural aging process. But we can help our bodies fight off as much damage as possible by giving our cells the weapons they need, in the form of antioxidants. These healthy substances, found in both animal and vegetable sources, appear to neutralize free radicals.

"A good example of this would be to look at the oxidation of an apple, when you cut it and it starts to get brown," said Sechrest. "If you dip it in orange juice, it stays white because of the Vitamin C in the orange juice."

In some cases, Sechrest says, antioxidants work by contributing an electron of its own to the unstable free radical.

"Research can't say yet that there's a clear-cut relationship in which taking in antioxidants will undo or eliminate a chronic illness, but we do know they are helpful," she said.

The wonderful thing about antioxidants is that they are found in tasty and easy-to-find foods. You won't have to consume buckets of tofu or fields of wheat grass to get the antioxidants you need. And although they can be found in supplements, it's best to get them from food. Animal sources such as fish oil, eggs and fortified milk provide Vitamins E, D, C and A, and plant sources including any deeply or brightly colored fruit or vegetable all provide antioxidants. Think prunes, blueberries, blackberries, strawberries, pomegranates, kale, spinach, broccoli, red bell peppers, cherries, red grapes, peas, corn, oranges and sweet potatoes. And-great news for chocoholics-cocoa powder (the kind use in baking) and dark chocolate are among the most powerful antioxidants, right up there with blackberries, blueberries and prunes.

A great way to incorporate antioxidants into your diet (beyond salad, that is), is with smoothies, easy to make with fresh or frozen fruit and yogurt or milk in a blender. Sechrest says that it's vital for parents to model good eating behavior for the next generation, so that kids will grow up making healthy food choices on their own.

"Simply buy good foods and expose your kids to them, and as years go by, they will continue to try new foods and elaborate on what they eat," she said.

In the mean time, the youngest picky eaters can get the antioxidants they need with a little clever thinking. Children love carrot cake. A few prunes can be finely chopped and added to brownies. Fresh spinach, also finely chopped, can be added to soup. Sechrest says that she even makes a meatloaf with shredded carrots, bell peppers and mushrooms.

But is there any hope for junk food junkies? Yes, says Sechrest. Just take it one fruit or vegetable at a time.

"The first step is to bring it home from the grocery store and commit to using it," she said.

And after drinking that smoothie or eating that salad, you can reward yourself with a square of delicious dark chocolate, guilt-free.