Calcium supplementation and vitamin D status appear to act largely together, not separately, to reduce the risk of colorectal adenoma recurrence. VDR genotype does not appear to be associated with risk.

Data regarding the association between folate status and risk of prostate cancer are sparse and conflicting. We studied prostate cancer occurrence in the Aspirin/Folate Polyp Prevention Study, a placebo-controlled randomized trial of aspirin and folic acid supplementation for the chemoprevention of colorectal adenomas conducted between July 6, 1994, and December 31, 2006. Participants were followed for up to 10.8 (median = 7.0, interquartile range = 6.0-7.8) years and asked periodically to report all illnesses and hospitalizations. Aspirin alone had no statistically significant effect on prostate cancer incidence, but there were marked differences according to folic acid treatment. Among the 643 men who were randomly assigned to placebo or supplementation with folic acid, the estimated probability of being diagnosed with prostate cancer over a 10-year period was 9.7% (95% confidence interval [CI] = 6.5% to 14.5%) in the folic acid group and 3.3% (95% CI = 1.7% to 6.4%) in the placebo group (age-adjusted hazard ratio = 2.63, 95% CI = 1.23 to 5.65, Wald test P = .01). In contrast, baseline dietary folate intake and plasma folate in nonmultivitamin users were inversely associated with risk of prostate cancer, although these associations did not attain statistical significance in adjusted analyses. These findings highlight the potential complex role of folate in prostate cancer and the possibly different effects of folic acid-containing supplements vs natural sources of folate.

Some serrated polyps of the colorectum are likely pre-invasive lesions, evolving through a newly recognized serrated pathway to colorectal cancer. To assess possible risk and protective factors for serrated polyps – and particularly to explore differences in risk factors between polyps in the right and left colorectum – we pooled data from three large multi-center chemoprevention trials. A serrated polyp (SP) was defined broadly as any serrated lesion (hyperplastic, sessile serrated adenoma, traditional serrated adenoma, mixed adenoma) diagnosed during each trial’s main treatment period, of about three to four years. Using generalized linear regression, we computed risk ratios and 95% confidence intervals (CI’s) as measures of the association between risk of serrated polyps and demographic, lifestyle, and dietary variables. Of the 2830 subjects that completed at least one follow-up exam after randomization, 675 (23.9 %) had at least one left sided serrated polyp and 261 (9.2 %) had at least one right sided lesion. In the left colorectum, obesity, cigarette smoking, dietary fat, total energy intake, and red meat intake were associated with an increased risk of serrated polyps. In the right colon, aspirin treatment was associated with a reduced risk and family history of polyps and folate treatment were associated with an increased risk of serrated polyps. Our results suggest that several common lifestyle and dietary variables are associated with risk of serrated polyps, and some of these may differ for the right and left colorectum.