John Nash Ott, in his book "Health & Light: the effects of natural & artificial light on man & other living things" throws light on the benefits of Ultraviolet rays. His experiments proved that sunlight absorbed through the eyes had dramatic effects on the pineal gland. Ultra-violet rays of the Sun helps in the cure of Leukemia. It is evident from the fact that in 1961, with five times the national average incidence, an elementary school in Niles I Illinois, was found to have the highest rate of leukemia of any school in the USA. Because of the intense glare from the sun, in the newly-constructed building in which glass had been used extensively, the teachers in two of the classrooms kept the blinds drawn and the children were exposed all day only to `warm-white` fluorescent light. All of the children with leukemia were being taught in these two classrooms. After several years of keeping the blinds drawn and the fluorescent lights on, the teachers in the two classrooms left and were replaced with teachers who preferred to let the sunlight in. At the same time, the warm-white fluorescent were replaced with cool-white lights. After that there were no further cases of leukemia reported in that School.
Also, it is best to get Sun exposure earlier in the day, rather than later in the day, if possible. That is because the bodys internal clock is regulated by sunlight, and requires early morning light for proper setting. Additional benefits of sun include better immune system function and this could be a part of the reason why it decreases cancer risk, since the immune system identifies and destroys abnormal cells as well as stronger bones and teeth, including significantly fewer cavities in children who get adequate sun exposure.