Furthermore, the sun triggers your skin to synthesize vitamin D. While vitamin D is found in foods, including fortified milk and cereals, cod liver oil, and certain fish, many people do not get enough of it from foods, so the sun provides most people with their vitamin D requirement. The catch is that sunscreen blocks the production of vitamin D.
With 10-15 minutes of sun exposure to the face, arms, hands, or back without sunscreen at least two times per week, most people can get an adequate level of vitamin D. However, people who live in northern or cloudy climates during certain times of the year may not be able to synthesize enough vitamin D from the sun.
Adequate levels of vitamin D prevent rickets in children and
in adults (both are diseases that weaken bones). In addition, vitamin D may help maintain a healthy immune system, promote normal cell growth, and prevent
Researchers do not yet know for sure, but some propose that increased levels of vitamin D associated with sun exposure may also have anti-cancer effects. In laboratory studies, vitamin D has been shown to inhibit cancer cell growth and induce death of cancer cells.