When local treatments for prostate cancer have failed, and prostate-specific antigen (PSA) rises in the absence of symptoms, there is little consensus as to the best management strategy.

Calcitriol has been shown to prolong the doubling time of PSA in this context, but near-toxic doses are required.

We investigated the effect of the nutrient vitamin D (cholecalciferol), a biochemical precursor of calcitriol, on PSA levels and the rate of rise of PSA in these patients.

Fifteen patients were given 2,000 IU (50 microg) of cholecalciferol daily and monitored prospectively every 2-3 months.

In 9 patients, PSA levels decreased or remained unchanged after the commencement of cholecalciferol. This was sustained for as long as 21 months.
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Higher Vitamin D Daily Dose Could Halve Colon Cancer Risk, UCSD researchers say

December 20, 2005 - Taking 1,000 international units (IU) of vitamin D 3 daily appears to lower an individual’s risk of developing colorectal cancer by 50 percent, according to cancer prevention specialists at the Moores Cancer Center at the University of California, San Diego (UCSD) Medical Center. Full story