Vitamin D and Colorectal Cancer
A number of studies have suggested that higher vitamin D intake, or higher circulating levels of vitamin D, may be associated with decreased risk of some cancers. To date, the evidence has been strongest for colorectal cancer. This study from EPIC is the largest of its kind to date and one of a few based on European populations. Vitamin D levels were measured in blood of 1248 subjects diagnosed with colorectal cancer and compared with levels measured in an equal number of control subjects, who were matched by sex, age, study centre, and some additional relevant variables. Higher blood vitamin D concentration showed a strong dose—response inverse association with colorectal cancer risk in both men and women. Subjects in the highest fifth of blood vitamin D levels showed a 40% reduced risk compared with those in the lowest fifth. When compared with a pre-defined mid-level concentration of vitamin D, subjects with very low levels showed a significantly higher risk of colorectal cancer development. In a follow-up study looking at survival after colorectal cancer diagnosis, subjects with higher blood vitamin D levels at baseline showed significantly longer survival. The strength of these observations lies in the large size of the study, and that blood samples were collected prior to any disease onset. The data suggest a role for vitamin D in colorectal cancer prevention, but in a similar way to pharmaceutical drugs, any public health advocacy of this should be based on clear and conclusive evidence from double-blind randomized trials.
Jenab M et al. Association between pre-diagnostic circulating vitamin D concentration and risk of colorectal cancer in European populations: a nested case-control study. BMJ. 2010 Jan 21;340:b5500. PMID: 20093284
Fedirko V et al. Prediagnostic 25-hydroxyvitamin D, VDR and CASR polymorphisms, and survival in patients with colorectal cancer in western European populations. Cancer Epidemiol Biomarkers Prev. 2012 Apr;21(4):582-93. PMID: 22278364