However a recent study published in the British Journal of Dermatology revealed that an epidemic of the disease has broken out among indoor workers. These workers get three to nine times LESS solar UV exposure than outdoor workers get, yet only the indoor workers have increasing rates of melanoma -- and the rates have been increasing since before 1940.
There are two major factors that help explain this, and the first has to do with the type of UV exposure.
There are two primary types of UV rays from sunlight, the vitamin-D-producing UVB rays and the skin-damaging UVA light. Both UVA and UVB can cause tanning and burning, although UVB does so far more rapidly. UVA, however, penetrates your skin more deeply than UVB, and may be a much more important factor in photo-aging, wrinkles and skin cancers.
A study in Medical Hypotheses suggested that indoor workers may have increased rates of melanoma because they're exposed to sunlight through windows, and only UVA light, unlike UVB, can pass through window glass. At the same time, these indoor workers are missing out on exposure to the beneficial UVB rays, and have lower levels of vitamin D.
"We hypothesize that one factor involves indoor exposures to UVA (321–400nm) passing through windows, which can cause mutations and can break down vitamin D3 formed after outdoor UVB (290–320nm) exposure, and the other factor involves low levels of cutaneous vitamin D3. After vitamin D3 forms, melanoma cells can convert it to the hormone, 1,25-dihydroxyvitamin D3, or calcitriol, which causes growth inhibition and apoptotic cell death in vitro and in vivo. … We agree that intense, intermittent outdoor UV overexposures and sunburns initiate CMM [cutaneous malignant melanoma]; we now propose that increased UVA exposures and inadequately maintained cutaneous levels of vitamin D3 promotes CMM."
To put it simply, UVB appears to be protective against melanoma -- or rather, the vitamin D your body produces in response to UVB radiation is protective.
As written in The Lancet (vol 363, issue 9410, pp 728-730):
"Paradoxically, outdoor workers have a decreased risk of melanoma compared with indoor workers, suggesting that chronic sunlight exposure can have a protective effect."
Your organs can convert the vitamin D in your bloodstream into calcitriol, which is the hormonal or activated version of vitamin D. Your organs then use it to repair damage, including damage from cancer cells and tumors. Vitamin D's protective effect against cancer works in multiple ways, including:
This applies not only to skin cancer but other types of cancer as well. Theories linking vitamin D to certain cancers have been tested and confirmed in more than 200 epidemiological studies, and understanding of its physiological basis stems from more than 2,500 laboratory studies, according to epidemiologist Cedric Garland, DrPH, professor of family and preventive medicine at the UC San Diego School of Medicine.
LIFE Clinic recommends using the sun therapeutically, this means getting the proper exposure to optimize your vitamin D levels. This typically means exposing enough of your unclothed skin surface to get a slight pink color on your skin. Your exact time will vary radically depending on many variables, such as you skin color, time of day, season, clouds, altitude and age.
The key principle is to never get burned, while still spending as much time as you can in the sun during the peak hours, as it is virtually impossible to overdose as long as you don't get burned.
The best time to be in the sun for vitamin D production is actually as near to solar noon as possible which is 1 PM in the summer for most (due to Daylight Saving Time). The more damaging UVA rays are quite constant during ALL hours of daylight, throughout the entire year -- unlike UVB, which are low in morning and evening and high at midday.
Most people with fair skin will max out their vitamin D production in just 10-20 minutes, or, again, when your skin starts turning the lightest shade of pink. Some will need less, others more. The darker your skin, the longer exposure you will need to optimize your vitamin D production.
If you work in an office, or get limited opportunities to go into the sun at peak hours, we recommend you have your Vitamin D levels checked, which can be done on a simple blood test. If they are low, they can be easily supplemented with a daily vitamin D3 capsule.
Optimizing your levels of Vitamin D3 may not only just protect against malignant melanoma, but has also been shown to reduce the risk of getting cancer of the colon, prostate, breast and lymphoma.