Fruits and vegetables

You may have heard it from your grandma, but now it's official! Eating plenty of fresh fruits and vegetables is good for your health. Fruits and vegetables are particularly important for preventing premature skin aging because they contain a wide variety of antioxidants. Many of the pigments responsible for the color of fruits and veggies are -- among other things -- potent antioxidants. These antioxidants help protect skin cells from damage by free radicals which are especially rampant in the skin due to environmental exposure (see also the article about antioxidant nutrients in this section). To ensure that your fruits and veggies have all their antioxidants intact, make sure they are fresh and uncooked (or only minimally cooked) since heat inactivates most antioxidants. Also, some fruits and veggies are significantly richer in antioxidants than others.
Fluids
A well-moisturized skin is somewhat less prone to developing of wrinkles. Drinking plenty of fluids throughout the day ensures proper hydration of the body and helps reduce skin dryness. Experts usually recommend drinking 6-8 glasses of water a day. Coffee and sodas are not a good substitute for water because they contain caffeine, which is a diuretic, i. e., a substance promoting the excretion of water via urine. Also, do not drink too much fluid 2-3 hours before going to bed. This may cause morning puffiness and excessively stretch your skin.
Calories
Except for frying oneself in direct sunlight at noon, the quickest way to get wrinkles is to put on a lot of weight and then lose it. The reason is obvious: when you gain weight, extra fat stretches the skin, then, when you lose weight and body fat goes away, the skin sags and crumples up. The degree of skin sagging after weight loss varies with the person's age (it tends to be worse the older you are), genetics and other factors. Let the desire to retain youthful skin be another incentive for you to watch your calories and avoid weight gain - even if you plan to lose weight later on. Also, keep in mind that gaining and losing weight in cycles may have negative effects not only on the skin but on your overall health as well.
Cooking
The central theme in cooking is heat-treatment of foods. As written in bold print in every college chemistry course, increasing temperature causes exponential increase in the rate of chemical reations. What does this mean to us, the eaters? Every time a food is heated up, the rate of reactions of degradation and oxidation of nutrients jumps up dramatically. In other words, cooking depletes food of many essential nutrients and antioxidants and increases the content of oxidative by-products (free radicals). As a result, we consume less essential nutrients and more aging-promoting free radicals. True, complete avoidance of cooked foods is no fun. You don't have to stop eating cooked foods altogether to avoid most of the negative effects of excessively cooked foods. For starters, reduce cooking time and avoid deep frying, grilling and cooking in large amounts of oil or fat.
For further details on how to change your diet and cooking habits in order to maximize skin benefits see Skin & Nutrition Infopack