Vitamin D Levels and Colorectal Cancer Risk
In a study reported in the Journal of the National Cancer Institute, McCullough et al found reduced risk for colorectal cancer with increasing levels of circulating 25-hydroxyvitamin D (25[OH]D).
Study Details
The study was an international pooling project using participant-level data from 17 separate cohorts, including 5,706 colorectal cancer case participants and 7,107 control participants with a wide range of circulating 25(OH)D concentrations. Levels of 25(OH)D were newly measured in 30% of participants; previously measured levels were calibrated to the same assay to allow risk estimation using absolute concentrations.
Associations With Colorectal Cancer Risk
Among all participants, compared with the lower range of sufficiency for bone health (50 to < 62.5 nmol/L), deficient 25(OH)D level (< 30 nmol/L) was associated with increased risk of colorectal cancer (relative risk [RR] = 1.31, 95% confidence interval [CI] = 1.05–1.62), whereas 25(OH)D above sufficiency (75 to < 87.5 and 87.5 to < 100 nmol/L) were associated with significantly reduced risk (RR = 0.81, 95% CI = 0.67–0.99; RR = 0.73, 95% CI = 0.59–0.91); no continued decline in risk was observed at levels of ≥ 100 nmol/L (3.5% of controls), with the risk reduction not being significant (RR = 0.91, 95% CI = 0.67–1.24, 3.5% of control participants). These associations were not markedly different in analysis adjusting for body mass index, physical activity, or other risk factors.
Overall, for each 25-nmol/L increase in circulating 25(OH)D, colorectal cancer risk was 19% lower in women (RR = 0.81, 95% CI = 0.75–0.87) and 7% lower in men (RR = 0.93, 95% CI = 0.86–1.00) (P = .008 for heterogeneity by sex). The inverse association between circulating level and colorectal cancer risk was observed in subgroups including colorectal cancer subsite, geographic region, and season of blood collection.
The investigators concluded, “Higher circulating 25(OH)D was related to a statistically significant, substantially lower colorectal cancer risk in women and nonstatistically significant lower risk in men. Optimal 25(OH)D concentrations for colorectal cancer risk reduction, 75–100 nmol/L, appear higher than current [Institute of Medicine] recommendations [based on bone health].”
The study was supported by grants from the National Cancer Institute; the National Heart, Blood, and Lung Institute; and by the National Cancer Institute Intramural Research Program.
Marjorie L. McCullough, ScD, of the Behavioral and Epidemiology Research Program, American Cancer Society, is the corresponding author for the Journal of the National Cancer Institute article.
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
