Q: We've heard a lot of talk about antioxidants being good for the body—and the skin. But if I'm a healthy person, and I take my daily supplements, do I really need antioxidants too?

Dr. Palmer: We all need—and use—oxygen to live. After we breathe it in, oxygen travels from our lungs to every cell in our body, helping to turn food into energy.

But oxygen can also have negative effects, whether you're healthy or not. Body cells are stable when their molecules have a full set of electrons. When oxygen enters the picture, though, they can lose an electron, becoming unstable or oxidized—the same chemical reaction that causes metal to rust. Losing an electron to a passing oxygen molecule converts that cell's molecule to an unstable, and damaging, atom known as a free radical.

Antioxidants are the body's main defense against free radicals. Antioxidants—which can be produced in the body or be obtained from food sources or, in the case of the skin, from topical products—donate missing electrons to free radicals and return them to a normal state.

Q: Why are free radicals so bad?

Dr. Palmer: Free radicals attack cells in the body. These attacks change the structure and function of cells and how they work. Cellular damage caused by free radicals is a key part of the aging process—and may even contribute to the development of some of our most prevalent diseases, including coronary artery disease and cancer.

When it comes to the skin, free radicals stimulate the production of enzymes, which break down collagen and elastin—triggering premature aging (wrinkles and sagging skin).

Q: Aren't free radicals caused by sun exposure?

Dr. Palmer: Yes, free radicals can be created in the body as a result of exposure to ultraviolet light (through sunlight or a tanning booth). But they can also be triggered through environmental exposure to cigarette smoke (breathing in secondhand smoke or even simply having it pass over the skin), car exhaust, factory pollution, pesticides (in our food and water supply), and insecticides (used in the home, our yards, and in the environment around us).

Poor diet (not eating enough fruits and vegetables and/or eating foods high in bad fats) can lead to the production of free radicals—as can lack of sleep and stress. Free radicals can also be formed while digesting large meals—why eating small, frequent meals is best.

Even exercise—though it's good for you—causes an increase in free radical production. Because of this, it's important to consume a diet high in antioxidants and to apply antioxidant products daily to your skin.