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This 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 life鈥檚 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. 鈥淭hey are very good antioxidants and they are particularly good at neutralising singlet oxygen [a type of ROS],鈥� says at the Leibniz Research Institute for Environmental Medicine in D眉sseldorf, Germany, who 50 years of data from human clinical trials involving carotenoid supplements. 鈥淭he carotenoids catch them and neutralise them before they can do damage.鈥�

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 can鈥檛 prevent the direct DNA damage caused by the rays themselves though, meaning they can鈥檛 be considered a replacement for sunscreen.

Good dietary sources include carrots and tomatoes. To get the greatest benefits, however, Krutmann recommends taking carotenoids as a nutritional supplement, especially if you drink alcohol, which depletes antioxidants in your skin.

Nutrients for skin

Besides carotenoids, healthy skin requires vitamin C too, found in foods such as citrus fruits. This helps by stimulating the production of collagen, the protein that gives skin its structure and firmness. Vitamin C also works with vitamin E (nuts and seeds are a good source of this) to protect natural fats known as lipids in our skin from becoming oxidised by ROS. 鈥淰itamin E sacrifices itself, so it gets oxidised in the place of the lipids,鈥� says , who researches regenerative medicine at North Carolina State University and has written a outlining the most important nutrients for skin health. 鈥淰itamin C then recycles vitamin E to its reduced form so that it is ready to protect the lipids again.鈥�

The NRF2 system can kick in when the skin is under attack and ramp up the production of antioxidants

This recycling process can take some time. Luckily, a secondary system called NRF2 鈥� named after the protein at its centre 鈥� can kick in when the skin is under attack and ramp up the production of other antioxidants. Polyphenols such as resveratrol, found in grapes and apples, and the substance sulphoraphane, present in broccoli and cauliflower, can activate this system.

Minerals such as selenium, manganese, copper and zinc can also increase the efficiency of the NRF2 pathway, making it work faster and more efficiently. They can be found in a range of foodstuffs, including nuts, legumes, grains and 鈥� you鈥檝e guessed it 鈥� fruit and veg.

Eating your greens may sound like age-old advice, but the build-up of pollution in our environment means that it has never been more important, says Valacchi. 鈥淥ur skin is the first organ to be affected, so we need to take even more care of it.鈥�