My dentist takes a daily baby aspirin & Vitamin D

My dentist has taken a daily baby aspirin for 20-25 years because of research showing reduction in colon cancer (his father died of colan cancer). Would that research be from CPS II data which demonstrated a decreased risk of colon cancer in people who take aspirin regularly?...

• Thun, M. J., Namboodiri, M. M. & Heath, C. W. Jr. Aspirin use and reduced risk of fatal colon cancer. N. Engl. J. Med. 325, 1593–1596 (1991). (cited in Ann M. Bode and Zigang Dong, 508, July 2009, Volume 9, www.nature.com/reviews/cancer)

He also takes a Vitamin D spray daily (as a dentist he works out of the sun!)