Circulating vitamin D and colorectal adenoma in asymptomatic average-risk individuals who underwent first screening colonoscopy: a case-control study.

BACKGROUND: A higher circulating vitamin D level is inversely associated with the risk of colorectal cancer, but the association with adenoma risk is less clear. AIMS: We examined the association between the circulating 25-hydroxyvitamin D(3) [25(OH)D(3)] concentration and colorectal adenoma in asymptomatic average-risk participants undergoing initial screening colonoscopy.
METHODS: The study subjects were comprised of 143 cases of colorectal adenomas and 143 age- and gender-matched controls with normal colonoscopy among the 586 asymptomatic average-risk subjects (median age, 58 years; range, 50-73 years) who underwent first screening colonoscopy and measurement of the serum 25(OH)D(3) between December 2009 and April 2010, consistent with winter months of the region.
RESULTS: The mean concentration of serum 25(OH)D(3) in the adenoma and control groups was 20.0 ± 11.0 ng/ml and 25.0 ± 20.0 ng/ml, respectively (P = 0.009). Using multivariate analysis, higher levels of 25(OH)D(3) were associated with a statistically significant decreased risk of colorectal adenoma after multivariable adjustment (highest vs. lowest quartile OR 0.38, 95% CI 0.18-0.80, P (trend) = 0.012). The inverse association of circulating 25(OH)D(3) with colorectal adenoma was stronger among the patients with proximal adenoma than that among the patients without proximal adenoma (highest vs. lowest quartile OR 0.29, 95% CI 0.13-0.66, P (trend) = 0.001).
CONCLUSIONS: The present study suggests that high levels of circulating vitamin D are associated with a decreased risk of colorectal adenoma, and especially adenoma located in the proximal colon.