Research over the last decade clearly documents that vitamin D is a premier modulator of immune function, helping to protect us from infection and at least 16 types of cancer. For example, recent research documents that white blood cells can convert ordinary vitamin D into an active form that is used to make a protein that kills tuberculosis bacteria. Perhaps more striking, however, is the role vitamin D plays in cancer prevention. As it happens, vitamin D is one of the most potent regulators of cell growth, working to prevent initiation and growth of cancerous cells and tumors. Vitamin D activates the “turn off” switch for many types of cancer cells, preventing uncontrolled growth. In fact, at a recent meeting of the American Association for Cancer Research, Dr. Edward Giovannucci of Harvard University challenged “…any of his colleagues to find an area or nutrient or any factor that has such consistent anti-cancer benefits as Vitamin D.” The data, as he notes, are really quite remarkable.
And just what are these data on vitamin D and cancer? For starters, as early as 1941 it was noted that people living in southern states with more sunshine had half the risk of dying from cancer as those living in northern, less sunny states. In 2002, this observation was further quantified in an article by William Grant published in the prestigious journal, Cancer. Using current data from the Atlas of Cancer Mortality, he again documented that residents of sunny southern areas, like the southwest, have half the risk of dying from 13 types of cancer as did residents of areas receiving less direct sun exposure, such as New England. And the concern with skin cancer from sunlight exposure? First of all, the sun exposure needed to improve vitamin D status is minimal. Vitamin D expert Dr. Michael Holick suggests 15 minutes of mid-day sun two or three times a week for light-skinned people, with more for those with dark skin. As for the risk-benefit ratio, it is now estimated that 30 times more cancer deaths are caused from a lack of sunshine exposure than from sun exposure. As Dr. Holick reports, 500 women die a year from non-melanoma skin cancer (likely related to sun exposure) while 27,500 die prematurely due to illnesses related to low vitamin D, often because of lack of sunlight. In other words, roughly 55 women die prematurely due to underexposure for every one death related to overexposure.
Even more convincing than the correlations between sunlight exposure and cancer is the direct association of higher vitamin D blood levels with less cancer incidence. For example, the large US Nurses’ Health Study found that women with the highest blood levels of vitamin D had half the risk of two of the three major types of colon cancer. And this cancer reduction benefit is not just for women. Garland and colleagues at the University of California, San Diego, reported a similar finding for men.
Breast cancer follows a similar pattern. In 2005, it was reported in the European Journal of Cancer that women with low levels of vitamin D were more than five times more likely to be diagnosed with breast cancer than were women with adequate levels. A similar five-fold increased risk for breast cancer in Caucasian women with low activated vitamin D was reported in 1999 by University of North Carolina researchers. Most recently, intervention studies supplementing with vitamin D have produced dramatic results. For example, in 2007 researchers at Creighton University reported the findings of the first intervention trial examining vitamin D and cancer. In this four-year, population-based, double-blind, randomized, placebo-controlled trial, postmenopausal women given 1,100 IU experienced a 60 to 77% reduction in the risk of developing any type of cancer.
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