UV & Free Radicals
Ultraviolet (UV) light refers to the UVA, UVB and UVC light that is either emitted by the sun or by specialised fluorescent lights.
Sunlight is mostly UVA (98%). Normal glass is almost transparent to UVA but blocks UVB and C. UVA has been linked to the destruction of collagen fibres and to the breakdown of Vitamin A and D in the skin. In the past UVA was considered less harmful than UVB but it is now known that they are both dangerous at high levels. Some scientists blame the absence of UVA filiters for the higher cancer risk that has been found for sunscreen users.
Our bodies need some UVB light for the synthesis of Vitamin D. This is a very important vitamin and is responsible for bone health, normal function of the nervous system, insulin production and many other key functions. Too much UVB exposure leads to DNA damage, sunburn and skin cancer. UVB also damages collagen but at a much slower rate than UVA.
Supplementing with oral Vitamin D will not generate the highly active form that your skin can synthesise. Your body needs some UVB light to keep you healthy. You won’t get this light from exposure to sunlight through glass. You should expose yourself to small amounts of open sun regularly. We recommend 10 to 15 minutes of sun, twice a week with the arms, face and back exposed and without sunscreen. With longer exposure to sun the levels of vitamin D reach an equilibrium in the skin and the vitamin is degraded as fast as it is produced.
This needs to be strictly controlled. Sunburn is devastating for your long term skin health. Overexposure to UV also compromises the skin’s immune system and damages the microflora on the skin’s surface.
Melanin absorbs UV and dissipates the energy as heat. Melanin is responsible for a tan. UVA light gives a quick tan that lasts for a few days by oxidising melanin that was already present. UVB stimulates the body to produce more melanin. This type of tan takes about two days to develop but lasts far longer.
Sunscreen
There is a lot of controversy over sunscreens at the moment. Many of them don’t provide sufficient UVA protection and there is also a debate over the benefits of chemical sunscreen use. A well controlled experiment in 2006 showed that the quantity of free radicals in the skin is higher in skin treated with sunscreen than in skin with no protection once the photoprotective chemicals in the sunscreen have been absorbed into the skin. This means that sunscreen use may increase the risk of malignant melanoma.
Lawsuits have been filed against sunscreen manufacturers in the US and this has led the US Food and Drug Administration to conclude that “the available evidence fails to show that sunscreen use alone prevents skin cancer”.
Vitamin D deficiency can also, ironically, lead to skin cancer. Application of sunscreen with an SPF of 8 inhibits vitamin D synthesis in the skin by 95%. Recent initiatives in Australia and New Zealand to encourage the use of sunscreen have resulted in increased vitamin D deficiency and have not resulted in a decrease in skin cancer rates.
All this would suggest that daily sunscreen use has questionable merits unless you’re outside most of the time and also suggests that sunscreens that use physical SPF factors are the way to go. Look for sunscreens that use zinc or titanium but make sure that the titanium particles are not nanoparticles as these have been linked to genetic damage that may cause cancer.
