Aside from its role in promoting calcium absorption, vitamin D-3, the active form of vitamin D, helps ensure that cells that have reached their normal life span are broken down and removed in a timely manner, according to Sarfraz Zaidi, M.D., author of the book "Power of Vitamin D." When vitamin D levels are deficient, the cycle of cell death and replacement can go awry, leading to potential cancer development. Another possible connection between vitamin D-3 and cancer involves insulin. The hormone insulin sends a strong signal to cells to grow and multiply. In situations of insulin resistance, high insulin levels lead to overgrowth of new cells. The combination of low vitamin D levels and high insulin levels may be responsible for promoting cancer development in some cases, Zaidi says.
Deficiency
Overwhelming evidence points to a close link between vitamin D deficiency and cancer. In particular, people with vitamin D deficiency show increased risk for colon, breast, prostate and ovarian cancer. Cancer deaths are also more prevalent in geographical locations with less sunshine and resultant higher rates of vitamin D deficiency. Similarly, your cancer survival rate is better if you are diagnosed in summer or autumn than in winter, possibly due to more available sunshine to contribute to the recovery process.
Lymphoma
Vitamin D may protect against lymphoma -- a group of cancers that affect the lymphatic cells of the immune system -- according to research conducted at the Cancer Prevention Institute of California. In the large cohort study of more than 120,000 teachers, 786 were diagnosed with one of three forms of lymphoma: non-Hodgkin's lymphoma, multiple myeloma or Hodgkin's lymphoma. Those who lived in areas of the state with high sunshine levels showed reduced risk. Skin sensitivity to sunlight, ethnicity, body mass and socioeconomic status did not affect cancer rates. Researchers concluded that mechanisms associated with exposure to ultraviolet rays, in addition to vitamin D, may contribute to lymphoma risk. The study appeared in the May 2011 issue of the journal "Blood."
Breast Cancer
Breast cancer risk may be increased in women with certain genetic variations in their vitamin D receptors, according to Jorg Reichrath, editor of the book "Vitamin D Analogs in Cancer Prevention and Therapy." As many as 70 percent of breast cancer types are associated with the genetic vitamin D receptor type that puts women at higher risk. Further studies are needed to better understand how the different receptor types influence the way the receptors function in order to develop an appropriate strategy for improving breast cancer treatments.
Abnormal Cell Growth
Activated vitamin D is a potent inhibitor of abnormal cell growth, says Michael F. Holick, M.D., author of the book "The Vitamin D Solution: A 3-Step Strategy to Cure Our Most Common Health Problem," but increased exposure to sunshine does not increase the kidneys' conversion of vitamin D to the active form. Instead, all of your body's cells have the ability to activate vitamin D. Prostate cancer cells exposed to the inactive form of vitamin D have been found capable of converting the inactive form into the active form, on the spot, instead of having to rely on the kidneys for the conversion. Similarly, colon, breast, lung and brain cells show the same ability to control their own active vitamin D supply. Holick adds that this delegation of authority prevents negative consequences of too much vitamin D conversion by the kidneys, such as excessive calcium absorption and overly high levels of calcium in the bloodstream.
References
- "Power of Vitamin D"; Sarfraz Zaidi; 2010
- "Blood"; Adulthood Residential Ultraviolet Radiation, Sun Sensitivity, Dietary Vitamin D, and Risk of Lymphoid Malignancies in the California Teachers Study; E. Chang, et al.; May 2011
- "Vitamin D Analogs in Cancer Prevention and Therapy"; Jörg Reichrath; 2003
- "The Vitamin D Solution: A 3-Step Strategy to Cure Our Most Common Health Problem"; Michael F. Holick, Ph.D., M.D.; 2003
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