Free radical damage is one of the principal mechanisms of aging. Free radicals are highly and indiscriminately reactive chemicals that can damage any structure in living cells. The most common source of free radicals is normal burning of fuel that occurs in every cell every minute of every day. (Generally, the more free radicals a species produces, the shorter its life span.) Skin suffers additional free radical damage from sunlight and pollutants. Topical antioxidants provide some protection against environmental damage to the skin and may be somewhat effective in slowing down the skin aging. However, topical antioxidants are relatively unreliable. Their effect depends on skin permeability, other ingredients in the cream and many other factors. It appears that increasing oral intake of some antioxidants may additionally protect skin from free radicals. Keep in mind, however, that relatively little solid research has been done specifically on skin benefits of oral or topical antioxidants and much of the supporting evidence is indirect.
A very important chemical property for an oxidant is its solubility in water and fat (or oil). Basically, living organisms have two types of internal media, watery extra- and intracellular space and oily membranes that serve as partitions enclosing individual cells and various intracellular compartments. Water-soluble antioxidants are effective mainly in extra- and intracellular fluid, whereas fat-soluble antioxidants protect biological membranes. Both types of antioxidants are needed to create an effective shield against free radicals for the entire body, and skin in particular.
Vitamin E is a principal fat soluble antioxidant vitamin in the body. It protects cellular membranes, lipoproteins and other “oily” structures. Skin is high in unsaturated fatty acids (“oily” molecules especially susceptible to free radical damage), and can benefit from vitamin E protection (both oral and topical).
Flavonoids are a diverse group of plant pigments with antioxidant properties. These substances are responsible for color in many fruits, vegetables and flowers. In addition to providing color that attracts insects or animals, these pigments protect plants from environmental stress. In addition to being potent antioxidants, some flavonoids have antiallergic, anti-carcinogenic, anti-viral and anti-inflammatory activity. Over 4,000 flavonoids have been characterized and classified, but only a few have been researched. As far as skin benefits are concerned, two classes of flavonoids appear to be especially beneficial: proanthocyanins (found in grapes and pine bark) and polyphenols (found in green tea).
Coenzyme Q10, lipoic acid, cysteine and methionine are potent antioxidants. But they also play other roles that are at least as important as their antioxidant activity. See also the article about conditionally essential nutrients in this section.
From Smart Skin Care
How do antioxidants affect the skin?
If you're like most people, you want smooth, healthy skin, but maybe you don't want to wade through hundreds of chemically laden products to get it. That's where antioxidants can help. Incorporating the right antioxidants into your diet and skin care routine can have a positive effect on your skin.
Antioxidants are nutrients (vitamins and minerals) and enzymes (proteins inside your body) that can help to prevent and repair damage to your body's tissue. Antioxidants do this by slowing or preventing the effect of free radicals, which start oxidation -- a process that causes damage from oxygen that can lead to cell dysfunction. If you've seen a peeled apple turn brown, you've seen oxidation in action. As antioxidants block the effects of free radicals, they end up being oxidized. This is why it's important to constantly replenish your supply of antioxidants.
Free radicals may also play a role in heart disease, cancer and other conditions [source: American Dietetic Association]. You can find antioxidants -- such as beta-carotene, lutein, lycopene, selenium and vitamins A, C and E -- naturally in many foods, including fruits and vegetables, nuts, grains, some meats, poultry and fish [source: MedlinePlus].
When it comes to caring for your skin, antioxidants can help to protect your skin from the damaging effects of the sun. Unlike sunscreens and moisturizers, antioxidants can protect your skin from the inside out by guarding your cells from damage. Vitamins A, C and E and the mineral selenium are thought to be particularly helpful in skin care. In addition to helping fortify cells against free radicals, vitamins A and C also encourage cell and tissue growth, helping the body to repair itself. This is very helpful to the skin, which is constantly shedding and regrowing cells. For this reason, any antioxidants that protect cells and encourage cell growth could be helpful in an anti-aging regimen, as they may help fight fine lines and wrinkles [source: WebMD].
Just like when adding any supplement to your diet, be careful when incorporating antioxidants into your daily routine. Though they are naturally good for you, antioxidants taken in excess can be harmful -- so be sure to follow the recommended amounts. In most cases, all you need to fulfill your body's quota for antioxidants is a healthy and balanced diet. In fact, it's a good idea to talk to your doctor before increasing your intake of any supplement.
For further study: Discovery Fit & Health