People the world over pay a pretty penny to look young. Many don't realise, however, that staving off wrinkles, age spots and thinning hair has little to do with cosmetic creams and lotions.

Take, for instance, the skin, the body's largest organ. "Twenty to 30% of changes in the skin are attributable to genetics," says Jean Krutmann, director of the Leibniz Research Institute for Environmental Medicine in Dusseldorf, Germany. "The other 70% to 80% are caused by environmental factors, for example ultraviolet radiation and air pollution."