Clinical Trial of Vitamin D3 to Reduce Cancer Risk in Postmenopausal Women

Hypotheses:

Primary: Increasing serum 25(OH)D from prevailing levels with vitamin D3 supplementation, while maintaining adequate calcium intake, will significantly decrease incidence of all-type cancer in a population sample of healthy postmenopausal women.

Secondary:

Increasing serum 25(OH)D from prevailing levels will significantly decrease incidence of specific cancers: breast, lung, colon, myeloma, leukemia, lymphoma.
Increasing serum 25OHD from prevailing levels will significantly decrease incidence of other disorders, specifically hypertension, cardiovascular disease, osteoarthritis, colonic adenomas, diabetes, upper respiratory infections and falls.

Specific Aims:

Determine the effect of supplementation with vitamin D3 on incidence of all types of cancer combined.
Determine in a nested-case control study the association of serum 25OHD collected at randomization and at the end of year one of study with risk of cancer over four years.
Sample randomly the population of healthy independently-living postmenopausal women 55 years and older from twelve adjacent rural counties in Nebraska.
Enroll a random sample of 2300 women into an intervention study, assign them randomly to one of two treatment groups: 1) vitamin D3 (2000 IU/d) and calcium (1500 mg/d), or 2) vitamin D3 placebo and calcium placebo, and to follow each study participant for four years.
Collect and store blood serum and white blood cells from every participant to test for genetic markers should the intervention be found effective in decreasing the incidence of cancer. Markers selected will be determined by the state of the science at the time of analysis.
Determine the effect of supplementation with calcium and vitamin D3 on incidence of specific cancers: breast, lung, colon, myeloma, leukemia, and lymphoma.
Determine the effect of supplementation on incidence of other disorders, specifically hypertension, cardiovascular disease, osteoarthritis, colonic adenomas, diabetes, upper respiratory infections, fractures, and falls.