eileen

OK Don has me on a new mission. If I'm interpeting this article correctly its suggesting moderation and the longer you take this path the less DNA damage you'll get from tanning. Anything else? Thanks :)

http://www.sciencedirect.com/science...1682ad789cdd23


Abstract Exposure to ultra violet radiation (UVR) is associated with significant long-term deleterious effects such as skin cancer. A well-recognised short-term consequence of UVR is increased skin pigmentation. Pigmentation, whether constitutive or facultative, has widely been viewed as photoprotective, largely because darkly pigmented skin is at a lower risk of photocarcinogenesis than fair skin. Research is increasingly suggesting that the relationship between pigmentation and photoprotection may be far more complex than previously assumed. For example, photoprotection against erythema and DNA damage has been shown to be independent of level of induced pigmentation in human white skin types. Growing evidence now suggests that UVR induced DNA photodamage, and its repair is one of the signals that stimulates melanogenesis and studies suggest that repeated exposure in skin type IV results in faster DNA repair in comparison to skin type II. These findings suggest that tanning may be a measure of inducible DNA repair capacity, and it is this rather than pigment per se which results in the lower incidence skin cancer observed in darker skinned individuals. This evokes the notion that epidermal pigmentation may in fact be the mammalian equivalent of a bacterial SOS response. Skin colour is one of most conspicuous ways in which humans vary yet the function of melanin remains controversial. Greater understanding of the role of pigmentation in skin is vital if one is to be able to give accurate advice to the general public about both the population at risk of skin carcinogenesis and also public perceptions of a tan as being healthy.

Don Smith

DNA "damage" is assessed by measuring the photoproducts, i.e., Cyclobutane Pyrimidine Dimers (CPD) and 6-4 dimers (but CPD's are by far the most common and important), that are produced by a dose of UVR. The narrow "peak" of the CPD AS (Action Spectrum) is 300 nm - 302 nm.

Traditional sunlamps have about the same amount of CPD-effective photons as sunlight at noon on a typical summer day while HID/high pressure sunlamps and new-era sunlamps only produce 30% (HID/hp) to 10% (new-era) of sunlight.

As your tolerance to UVR (TUVR) increases, your sensitivty to UVR (SUVR) decreases. An increase in TUVR comes from (a) darker skin type/subtype (darker natural skin color) and (b) the development of facultative (acquired) pigmentation (a.k.a., a "tan"). An increase in TUVR (and a decrease in SUVR) means that you are reducing the potential for DNA damage.

In the October issue of Looking Fit we will show "how and why" your TUVR increases (and your SUVR decreases) in direct relation to (a) your skin type/subtype and (b) your level of tan. Our data shows that a skin type 3B (the most common Caucasian skin subtype) with a "maximum" tan level reduces his SUVR by 90%.

The "bottom line" is that your "best friend" if you want to prevent DNA "damage" is a deep, dark year-round tan (and you get the "fringe" benefit of helping to maintain an optimal vitamin D level and you will look and feel good).