According to Mercola.com:
Theories linking vitamin D deficiency to cancer 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.
Optimizing your vitamin D levels could help you to prevent at least 16 different types of cancer including pancreatic, lung, ovarian, prostate, and skin cancers. Overall, optimal vitamin D levels can cut cancer risk by as much as 60 percent, according to one large-scale, randomized, placebo-controlled study.
The most important factor is your vitamin D serum level. In order to help prevent a wide variety of diseases and health ailments, your vitamin D level needs to be between 50 and 70 ng/ml year-round.
The ideal way to optimize your vitamin D level is through sun exposure. As a very general guide, you need to expose a substantial amount of your entire body, when the sun is at its zenith.
According to recent findings from the D* Action study, adults need about 8,000 IU’s of oral vitamin D3 per day in order to get serum levels above 40 ng/ml.
Natural sunlight is the best source of vitamin D! UV sunlight is the fuel that enables the body to make vitamin D, but how long should you stay in the sun to optimize your Vitamin D without sun protection?
Skincare experts at SkinHealth Technology, LLC have developed a patented, new concept that enables you to attain vitamin D development 100% naturally–without damage to the skin. To accurately gauge the necessary length of time in the sun, simply apply one of their Natural Vitamin D UV Activation Sensors to skin or clothing. When the sensor turns red and the sun symbol disappears —it’s time to apply sunscreen or get out of the sun.