Vitamin D is essential for the formation, growth, and repair of bones and for normal calcium absorption and immune function. It is obtained primarily through exposure of the skin to ultraviolet radiation in sunlight, but it can also be obtained from some foods and dietary supplements. Some recent research suggests vitamin D may be able to stop or prevent cancer. Now, a new study finds an enzyme that plays a role in metabolizing vitamin D can predict lung cancer survival. The study, from researchers at the University of Michigan Comprehensive Cancer Center, suggests that this enzyme stops the anti-cancer effects of vitamin D. Levels of the enzyme, called CYP24A1, were elevated as much as 50 times in lung adenocarcinoma compared with normal lung tissue. The higher the level of CYP24A1, the more likely tumors were to be aggressive. About a third of lung cancer patients had high levels of the enzyme. After five years, those patients had nearly half the survival rate as patients with low levels of the enzyme.