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Enjoying Your Day in the Sun: Defending Skin from the Inside Out
By: Kimberly Decker
Posted: May 4, 2011, from the May 2011 issue of GCI Magazine.
page 2 of 6When you think of sunlight and skin damage, you tend to think first of the UV spectrum. Within the UV range, UVA rays are the longest and, until recently, were thought to be the least harmful. However, new studies indicate that UVA is quite damaging, because it can contribute to collagen breakdown and, notably, DNA damage in melanocytes—which can lead to cancer. Furthermore, UVA radiation can pass through windows both at home and in the car while driving, causing extensive damage. UVB rays, with midrange wavelength, are associated with skin cancers such as melanoma, as well as the reddening, or erythema, of sunburn. The shortest and most dangerous are the UVC rays, and though the ozone layer has historically blocked this spectrum, continual depletion of that barrier may render them a worrisome new consideration for those concerned about skin health.
How light rays age skin involves a basic process of photooxidation. As David Djerassi, wellness and nutricosmetic expert for LycoRed, Ltd., Beer Sheva, Israel, explains, “UV light penetrates the skin, causing the formation of UV-induced free radicals.” Among these is singlet oxygen, a harmful reactive oxygen species, or ROS, that tips the skin’s homeostasis off balance—destroying tissues, oxidizing lipids, cleaving genes and setting off a chain reaction that generates additional harmful reactive species, including hydroxyl radicals and superoxide anion. “There is also new information suggesting that only 50% of the free radicals generated in skin are caused by exposure to UVB and UVA radiation, and the other 50% are caused by visible light,” Djerassi adds.
As with chronological aging, photoaging manifests in external and internal effects: reduced cell turnover, delayed wound healing, cross-linking of collagen, loss of skin elasticity, dermal thinning, roughness and blotchiness. But photoaging assaults skin further still. The oxidative stress initiates inflammation and reddening that shows up as erythema. In the dermis, or inner layer of skin, UV light triggers the buildup of abnormal elastin damage and breaks down collagen at a faster rate than natural aging; eventually, these disorganized proteins show up as solar scars and, with time and continued accumulation, become wrinkles. And perhaps most worrisome, the sun attacks the skin’s genes, mutating mitochondrial and nuclear DNA so as to increase cell dysfunction and death and possibly precipitate skin cancer.
It doesn’t take much exposure to set these events into motion. Not only do studies show that the sun time during a conservative vacation accounts for only about a third of the annual average UV dose—another reminder that most UV exposure takes place at home, every day—but, says Djerassi, “Clinical evidence demonstrates that just one day of unprotected sun exposure can cause irreversible cell damage, which is associated with both morphological and histological changes. These changes can lead to premature aging of the skin.” And they offer further proof that you need more sun protection than you think.
Protection From the Inside Out
Typically, sun protection has taken an exogenous form—coming from the outside by way of clothing or topical sunscreens. But long sleeves and pants aren’t always practical, and studies of the composition of sunscreens show that only 16% of those currently marketed contain both UVA- and UVB-filtering ingredients. As much as 13% of the sunscreens with a sun-protection factor, or SPF, of at least 30 screen only UVB rays, lacking any ingredients to block the aging and DNA-damaging UVA. And as if that weren’t enough, analyses reveal that fully 54% of available sunscreens contain UV-blocking ingredients that themselves are vulnerable to photooxidation, breaking down in a matter of hours or sometimes even minutes.