Epidemiology of vitamin D and colorectal cancer: Casual or causal link? –

The Journal of Steroid Biochemistry and Molecular Biology
doi:10.1016/j.jsbmb.2010.03.085 | Copyright © 2010 Elsevier Ltd All rights reserved.
Edward Giovannuccia, b, Corresponding Author Contact Information, E-mail The Corresponding Author
a Harvard School of Public Health, United States
b Channing Laboratory, Brigham and Women's Hospital/Harvard Medical School, United States
Received 4 November 2009; accepted 26 March 2010. Available online 14 April 2010.

Introduction
Since Garland and Garland hypothesized that better vitamin D status lowered risk of colorectal cancer in 1980, the relation between vitamin D status and colorectal cancer risk has been investigated in epidemiologic studies. These studies are reviewed.

Materials and methods
Various approaches have been used to estimate vitamin D status, including direct measures of circulating 25(OH)vitamin D levels, surrogates or determinants of vitamin D (including region of residence, intake, and sun exposure estimates, or a combination of these). These measures of vitamin D status have been studied in relation to colorectal adenoma, cancer incidence and mortality.

Results
In general, all lines of inquiry from observational studies indicate that an association between better vitamin D status and lower colorectal cancer risk exists. While most of the studies have examined vitamin D status in relation to risk of cancer, some evidence suggests that vitamin D may be additionally important for colorectal cancer progression and mortality.

Discussion
Although confounding factors cannot be entirely excluded, the consistency of the association using various approaches to measure vitamin D, for diverse endpoints and in diverse populations shows high consistency and is suggestive of a causal association. Thus, improving vitamin D status could be potentially beneficial against colorectal cancer incidence and mortality.

Article Outline

1. Introduction
2. Geographic studies
3. Nested case–control studies of 25(OH)D and colorectal cancer or adenoma risk
4. Predicted 25(OH)D level
5. Studies based on dietary and supplementary vitamin D intake
6. Randomized controlled trials
7. Vitamin D and survival from colorectal cancer
8. Biologic plausibility of an association between vitamin D and colorectal cancer
9. Conclusions
References

Special issue selected article from the 14th Vitamin D Workshop held at Brugge, Belgium on October 4–8, 2009.