Total and free circulating Vitamin D and Vitamin D-binding protein in relation to colorectal cancer risk in a prospective study of African Americans

Background: Previous studies rarely evaluated the associations between Vitamin D-binding protein and free Vitamin D with colorectal cancer risk. We assessed these biomarkers and total 25- hydroxyVitamin D in relation to colorectal cancer risk in a sample of African Americans. Methods: Cases comprised 224 African American participants of the Southern Community Cohort Study diagnosed with incident colorectal cancer. Controls (N = 440) were selected through incidence density sampling and matched to cases on age, sex, and race. Conditional logistic regression was used to calculate odds ratios (OR) and 95% confidence intervals (CI) for associations between biomarker levels and colorectal cancer risk. Results: Vitamin D was inversely associated with colorectal cancer risk where the OR per-SD increase in total and free 25- hydroxyVitamin D were 0.82 (95% CI, 0.66-1.02) and 0.82 (95% CI, 0.66-1.01), respectively. Associations were most apparent among cases diagnosed <3 years after blood draw: ORs for the highest tertile versus the lowest were 0.69 (95% CI, 0.21-0.93) for total 25-hydroxyVitamin D and 0.71 (95% CI, 0.53-0.97) for free 25-hydroxyVitamin D. Inverse associations were seen in strata defined by sex, BMI, and anatomic site, although not all findings were statistically significant. Vitamin D-binding protein was not associated with colorectal cancer risk. Conclusions: Our findings suggest that total and free 25-hydroxyVitamin D may be inversely associated with colorectal cancer risk among African Americans. Impact: These findings highlight a potential role for Vitamin D in colorectal cancer prevention in African Americans.