Here at iToBoS, we strongly suggest you avoid getting a suntan. You certainly need some sunshine in your life, but UV dose high enough to cause a tan is already much higher than the dose needed for vitamin D production.
Excess UV exposure is estimated to contribute to 95% of melanomas and 99% of non-melanoma skin cancers. A tan forms when ultraviolet (UV) rays from the sun discharge too much energy into our skin. The excess energy of UVB rays, which penetrate the upper layers of our skin, distorts the DNA and prevents it from copying correctly when the cells multiply, which can cause mutations.
UVA rays, which penetrate deeper into the skin, can trigger a harmful process called oxidative free radical damage, which can damage not just DNA but also many of the skin’s structural components like collagen. This is the kind of UV exposure that causes premature ageing.
A single day’s sun exposure can cause up to 100,000 defects in the DNA of each skin cell. The same damage can be caused by sunbeds and solariums.
Once their DNA repair mechanisms detect large amounts of damage, skin cells signal pigment-producing cells (melanocytes) to start producing extra melanin. Melanin is parcelled up and transported into other skin cells to protect their DNA, by settling over the cell nucleus like an umbrella. This filters some UV rays and gives tanned skin its brown colour. But don’t rely on a tan to protect you fully – it’s only as protective as SPF 2 sunscreen.
Many people find a tanned look attractive, and luckily there is a safe way to indulge in the aesthetics of golden-brown skin. Any bottle or spray tan with the active ingredient dihydroxyacetone is safe to use because the active ingredient doesn’t penetrate below the layer of dead cells on the top of your skin. This colourless sugar molecule turns brown when it reacts with amino acids in the skin, and is shed as the old skin flakes off.
So how do you protect your skin and still get the health benefits of sunshine? There are two parts to sun-safe behaviour developed in Australia, and the same principles apply elsewhere in the world too.
First, every day when the UV index in your area is 3 or higher, you should wear sunscreen everywhere that isn’t covered by that day’s outfit. This prevents the damage accumulated by short exposures, day in and day out. Check your local weather report to find out the UV index where you are today. During the cooler months in places where the UV index is often below 3, it’s good to spend some time on most days, in the middle of the day, with skin exposed to the sun to maintain healthy vitamin D levels.
Second, if you’re planning to be outside for a prolonged time, you should follow the Slip Slop Slap Seek Slide advice. Slip on a long-sleeved shirt, slop on sunscreen, slap on a hat, seek shade and slide on some sunglasses. Reapply your sunscreen every two hours, and be sure to use plenty: you want about a teaspoon each for your back, chest, head/neck, and each arm and leg.
Katie Lee, University of Queensland.