I have done extensive research on that topic and obviously, it's not easy to find any reliable sources.
Look into sun gazing - an ancient knowledge of gaining life energy from staring directly into the sun. It should be done early during sunrise or late during the sundown and must be done by a short period of time daily, with gradual increments. Many people have surprising effects: from heath to spiritual.

Extensive sunbathing is not healthy but according to studies, the majority of the people are deficient in vitamin D plus all those sun-blocking creams are highly carcinogenic.