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.