OLIC ACID AND ITS DERIVATIVES (folate) are essential nutrients in humans and play an important role in nucleotide synthesis and methylation reactions. 1 Folate deficiency leads to macrocytic anemia, and abundant evidence indicates that even in well-nourished western populations, folate supplementation reduces the risk of neural tube defects. 2 Considerable epidemiological evidence suggests that a low-folate diet is associated with an increased risk of colorectal neoplasia, 3-5 particularly in concert with alcohol, which can antagonize the metabolism of folate. 6,7 Much animal data support an antineoplastic effect of folate. However, in some animal studies, folate deficiency protects against, and supplementation increases, experimental carcinogenesis. 3 For editorial comment see p 2408.
BACKGROUND Epidemiologic and preclinical data suggest that higher intake and serum levels of vitamin D and higher intake of calcium reduce the risk of colorectal neoplasia. To further study the chemopreventive potential of these nutrients, we conducted a randomized, double-blind, placebo-controlled trial of supplementation with vitamin D, calcium, or both for the prevention of colorectal adenomas. METHODS We recruited patients with recently diagnosed adenomas and no known colorectal polyps remaining after complete colonoscopy. We randomly assigned 2259 participants to receive daily vitamin D3 (1000 IU), calcium as carbonate (1200 mg), both, or neither in a partial 2×2 factorial design. Women could elect to receive calcium plus random assignment to vitamin D or placebo. Follow-up colonoscopy was anticipated to be performed 3 or 5 years after the baseline examinations, according to the endoscopist’s recommendation. The primary end point was adenomas diagnosed in the interval from randomization through the anticipated surveillance colonoscopy. RESULTS Participants who were randomly assigned to receive vitamin D had a mean net increase in serum 25-hydroxyvitamin D levels of 7.83 ng per milliliter, relative to participants given placebo. Overall, 43% of participants had one or more adenomas diagnosed during follow-up. The adjusted risk ratios for recurrent adenomas were 0.99 (95% confidence interval [CI], 0.89 to 1.09) with vitamin D versus no vitamin D, 0.95 (95% CI, 0.85 to 1.06) with calcium versus no calcium, and 0.93 (95% CI, 0.80 to 1.08) with both agents versus neither agent. The findings for advanced adenomas were similar. There were few serious adverse events. CONCLUSIONS Daily supplementation with vitamin D3 (1000 IU), calcium (1200 mg), or both after removal of colorectal adenomas did not significantly reduce the risk of recurrent colorectal adenomas over a period of 3 to 5 years. (Funded by the National Cancer Institute; ClinicalTrials.gov number, NCT00153816.)
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.
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