Prof. Michael Holick, a world reknown dermatologist, claims in his book "The UV Advantage" that avoiding the sun altogether can be potentially harmful for our health. He proves that the advantages gained from a short exposure substantially outweight the risk of getting a skin cancer. His research has shown that sunbathing can prevent many types of cancer, including breast cancer, because vitamin D (calciferol) which is only produced when the UV rays hit the skin prevents uncontrollable cell divisions. Moreover, the research has revealed that for every cancer caused because of the excessive sun exposure fall 30 cases of illness caused by sun deficiency! His findings have led the American Cancer Society to withdraw the recommendations of no UV exposure.
Vitamin D is essential for calcium absorbtion, healthy nervous system, strong muscles and heart. It also has anti-inflammatory properties and helps cure joint pain, allergies and diabetes. Plus, it stimulates the ovaries and our fertility, as well as lowers the level of stress hormones like hydrocortisone and adrenaline in the bloodstream, which affects our mood positively.
The key to safe sun bathing is the time spent outside, which should not exceed 10 to 15 minutes a day depending on your skin type. Also, remember that the effectiveness of sunscreens quickly decreases with a higher factor: SPF 5 neutralizes 70% of UV rays, SPF 10 85%, SPF 15 93%, while SPF 50 about 98%. This means the most common SPF 15 sunscreen is almost as good as the much more expensive SPF 50!
Info source: Polish edition of Shape, July 2009.