Vitamin D insufficiency is widespread, and is thought to contribute to a variety of disease states, including osteoporosis, cardiovascular disease, diabetes, autoimmune diseases, depression, and cancers.
Vitamin D affects calcium absorption and metabolism in the bone, kidney, and intestine, but it also acts as a regulator of gene transcription in many tissues, affecting genes that control cell growth, adhesion, differentiation, proliferation, and programmed cell death. Vitamin D’s action on such genes has been shown to suppress proliferation of human colon cancer cells and tumor growth.1,2
Also, the cells of the colon, whether they are normal or cancerous, are capable of converting 25(OH)D to its active form 1,25(OH)2D. It is likely that this ability has purpose – vitamin D may have yet unidentified actions specific to the cells of the colon.
Researchers analyzed data from the European Prospective Investigation into Cancer and Nutrition (EPIC) study, which has over 520,000 participants. Blood levels of vitamin D, which were measured at the start of the study, were compared between 1248 colorectal cancer patients and matched controls after diagnosis.
Circulating 25(OH)D levels of below 20 ng/ml were associated with increased risk of colorectal cancer compared with levels between 20-30 ng/ml. When the researchers arranged the data into 5 quintiles of Vitamin D levels, they found a dose-dependent reduction in colon cancer risk; highest quintile (greater than 40 ng/ml) had 40% reduced risk compared to lowest quintile (less than 10 ng/ml). When cancers were distinguished by site, the association between Vitamin D levels and colon cancer was even stronger – the highest quintile showed a 60% risk reduction.3
This large study followed up at least 25 previous studies since 2002. A 2009 review of these previous studies confirmed that there is indeed an inverse relationship between vitamin D levels and colorectal cancer. Even after a diagnosis of colon cancer, vitamin D levels are associated with increased survival – in colon cancer patients, higher vitamin D levels were predictive of a decreased risk of death from any cause, not only colon cancer.4
The 2009 review concluded that 25(OH)D levels of 32 ng/ml would be sufficient to achieve the protection against colorectal cancers seen in the literature, and the most recent study cited saw benefits with as low as 20 ng/ml. A minimum of 30 ng/ml 25(OH)D is thought to be required for vitamin D to properly exert its many beneficial effects.5 Accordingly, I recommend that levels be maintained in the range of 35-55 ng/ml.
About 50% of the U.S. population is deficient in vitamin D and cannot rely on sun exposure because of indoor jobs, skin color, and their climate. Plus, with the depletion of the ozone layer, the amount of sun most people would require to achieve these levels may result in too much skin damage and skin cancer.6
1. Ingraham BA, Bragdon B, Nohe A. Molecular basis of the potential of vitamin D to prevent cancer. Curr Med Res Opin. 2008 Jan;24(1):139-49.
2. Journal of Clinical Investigation (2009, July 7). Understanding The Anticancer Effects Of Vitamin D3. ScienceDaily. Retrieved April 6, 2010, from http://www.sciencedaily.com /releases/2009/07/090706171500.htm
Emory University (2008, April 14). Vitamin D And Calcium Influence Cell Death In The Colon, Researchers Find. ScienceDaily. Retrieved April 6, 2010, from http://www.sciencedaily.com /releases/2008/04/080413161052.htm
Rockefeller University Press (2008, November 26). Vitamin D Can Alter Color Cancer Cells In Many Ways, Through One Pathway. ScienceDaily. Retrieved April 6, 2010, from http://www.sciencedaily.com /releases/2008/11/081117091614.htm
3. Jenab M, Bueno-de-Mesquita HB, Ferrari P, 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.
High vitamin D levels linked to lower risk of colon cancer. ScienceDaily. Retrieved April 6, 2010, from http://www.sciencedaily.com /releases/2010/01/100122002340.htm
4. Dana-Farber Cancer Institute (2008, June 20). Vitamin D Linked To Colon Cancer Survival. ScienceDaily. Retrieved April 6, 2010, from http://www.sciencedaily.com /releases/2008/06/080619090749.htm
5. Holick MF, Chen TC. Vitamin D deficiency: a worldwide problem with health consequences.Am J Clin Nutr 2008;87(suppl):1080S– 6S.
6. Terushkin V, Bender A, Psaty EL, et al. Estimated equivalency of vitamin D production from natural sun exposure versus oral vitamin D supplementation across seasons at two US latitudes. J Am Acad Dermatol. 2010 Apr 2. [Epub ahead of print]