A protective effect of vitamin D against cancers was first proposed in 1980, based on an earlier observation that colon cancer mortality was the highest in geographical areas exposed to the least amounts of sunlight.2,3 Several more studies of geographical variations in cancers have found the same result: inverse relationships exist between sun exposure and 24 types of cancer, including the most common cancers – those of the breast, colon, rectum, and prostate.4,5
Since 1980, evidence for the involvement of vitamin D in the relationship between sun exposure and decreased cancer risk has progressively accumulated, as associations were found between blood vitamin D levels and reduced risk of cancers.6,7 Further support for the importance of vitamin D in cancer prevention was provided by randomized controlled trials of vitamin D supplementation that showed reduced cancer risk compared to placebo. There have also been many reports that vitamin D receptor gene mutations, which interfere with the normal biological actions of vitamin D, were associated with increased cancer risk.8-10
Additional studies confirmed that vitamin D has growth-inhibitory effects on cells derived from breast, colon, prostate, and skin cancers.11 Vitamin D can block cancer cell growth in a number of ways: Vitamin D alters the expression of genes that regulate inflammation, cell death and cell proliferation, and also interferes with the growth-promoting actions of IGF-1 and other growth factors. Additional anti-cancer effects of vitamin D include enhanced DNA repair and immune defenses, and angiogenesis inhibition.12
Today, over 800 scientific papers have been published on the relationship between vitamin D and cancers. We now have ample evidence that maintaining adequate vitamin D levels is an effective strategy for protection against cancer. (Please see references below drfuhrman.com)
You can get Vitamin D through multivitamins, but I recommend Cod Liver Oil. Once a standard supplement in traditional European societies, cod liver oil provides fat-soluble vitamins A and D, which found present in the diet of primitives in amounts ten times higher than in modernized diets. Cod liver oil supplements are a must for women and their male partners, to be taken for several months before conception, and for women during pregnancy. Growing children will also benefit greatly from a small daily dose.
Cod liver oil is also rich in eicosapentaenoic acid (EPA) and docasahexaenoic acid (DHA). The body makes these fatty acids from omega-3 linolenic acid. EPA is as an important link in the chain of fatty acids that ultimately results in prostaglandins, localized tissue hormones while DHA is very important for the proper function of the brain and nervous system. Those individuals who have consumed large amounts of polyunsaturated oils, especially partially hydrogenated oils, who are suffering from certain nutrient deficiencies, or who have impaired pancreatic function, such as diabetics, may not be able to produce EPA and DHA and will, therefore, lack important prostaglandins and necessary fats for the brain unless they consume oily fish or take a cod liver oil supplement. You can find more information here at the Weston A. Price Foundation
2. Garland CF, Garland FC. Do sunlight and vitamin D reduce the likelihood of colon cancer? Int J Epidemiol 1980;9:227-231.
3. Apperly FL. The Relation of Solar Radiation to Cancer Mortality in North America. Cancer Res 1941;1:191-195.
4. Grant WB, Garland CF. The association of solar ultraviolet B (UVB) with reducing risk of cancer: multifactorial ecologic analysis of geographic variation in age-adjusted cancer mortality rates. Anticancer Res 2006;26:2687-2699.
5. Grant WB. Ecological studies of the UVB-vitamin D-cancer hypothesis. Anticancer Res 2012;32:223-236.
6. Gandini S, Boniol M, Haukka J, et al. Meta-analysis of observational studies of serum 25-hyd roxyvitamin D levels and colorectal, breast and prostate cancer and colorectal adenoma. Int J Cancer 2011;128:1414-1424.
7. Grant WB. Relation between prediagnostic serum 25-hydroxyvitamin D level and incidence of breast, colorectal, and other cancers. J Photochem Photobiol B 2010;101:130-136.
8. Kostner K, Denzer N, Muller CS, et al. The relevance of vitamin D receptor (VDR) gene polymorphisms for cancer: a review of the literature. Anticancer Res 2009;29:3511-3536.
9. Lappe JM, Travers-Gustafson D, Davies KM, et al. Vitamin D and calcium supplementation reduces cancer risk: results of a randomized trial. Am J Clin Nutr 2007;85:1586-1591.
10. Bolland MJ, Grey A, Gamble GD, et al. Calcium and vitamin D supplements and health outcomes: a reanalysis of the Women's Health Initiative (WHI) limited-access data set. Am J Clin Nutr 2011;94:1144-1149.
11. Fleet JC. Molecular actions of vitamin D contributing to cancer prevention. Mol Aspects Med 2008;29 :388-396.
12. Fleet JC, DeSmet M, Johnson R, et al. Vitamin D and cancer: a review of molecular mechanisms. Biochem J 2012;441:61-76.
13. Tripkovic L, Lambert H, Hart K, et al. Comparison of vitamin D2 and vitamin D3 supplementation in raising serum 25-hydroxyvitamin D status: a systematic review and meta-analysis. Am J Clin Nutr 2012.