A multicoloured dietcan lead to a brighter complexionColdsnowstorm/Getty ImagesThis article is part of a special issue investigating key questions about skincare. Find the full series here.Your skin is under constant assault. Exhaust fumes, cigarette smoke, particulate pollution, heavy metals and ozone can generate reactive oxygen species (ROS) that attack DNA, rupture cell membranes and unravel lifes essential proteins. Perhaps the most harmful are UV rays, which generate ROS as well as disrupting DNA directly.The human body can mop up ROS and neutralise them, but it needs molecules found in fruit, vegetables and leafy greens to do so.Carotenoids are among the nutrients that have been most extensively studied for these benefits. These are the pigments that give the likes of pumpkins their bright colour. They are very good antioxidants and they are particularly good at neutralising singlet oxygen [a type of ROS], says Jean Krutmann at the Leibniz Research Institute for Environmental Medicine in Dsseldorf, Germany, who recently analysed 50 years of data from human clinical trials involving carotenoid supplements. The carotenoids catch them and neutralise them before they can do damage.These substances are best at protecting against longer wavelengths found in UVA light. UVA penetrates the deepest layers of the skin, generating ROS that can cause skin ageing, wrinkling and cancers. Carotenoids cant prevent the direct DNA damage caused by the rays themselves though, meaning they cant be considered a replacement for sunscreen.Good dietary sources include carrots and tomatoes. To get the greatest benefits,