yes Vitamin D reduces cancer risk, The AICR (American Institute for Cancer Research) found that Vitamin D is the key for reducing cancer risk. They cant tell how much but the current daily recommended amount of 400 international units would not be enough and the new coming numbers are going to show a vitamin D deficiency in most Americans.

Sun and water mean life, all creatures seek sun and water, so instinctively i would say "Yes Vitamin D is good for your well being"