New research confirms that the link between Vitamin D and breast cancer is indeed a powerful one, suggesting that women with high levels of the vitamin could have a significantly lower risk of developing the disease.
The most recent review of the ongoing research on the Vitamin D/breast cancer connection, published in the September 2011 issue of Anticancer Research, analyzed data from 11 case-control studies. The researchers combined the data from all of the studies to calculate the effect of Vitamin D levels on the risk of breast cancer development.
The results of the data analysis indicate that high Vitamin D levels definitely reduce the risk of breast cancer, with women whose blood levels were highest being at 50 to 70 percent lower risk for the disease than women whose levels of the vitamin were the lowest.
These findings confirm the results of a large number of epidemiological studies, including geographical correlation studies, randomized clinical trials, and observational and laboratory studies that show Vitamin D has a measurable impact on the incidence of cancer.
The Vitamin D/cancer link was initially discovered through geographical correlation studies, which compared cancer frequency and the death rate of populations in northern and southern latitudes. These studies indicated that southern latitude populations that had more sun exposure had a lower cancer incidence and death rate than northern latitude populations. Researchers hypotheisized that the the production of Vitamin D, which is stimulated by exposure to sunlight, could be causal.
These studies were followed by further investigation into the connection between the vitamin and the risk and severity of cancer development. Observational studies appear to support the findings of the geographic correlation research (though their conclusions cannot be considered entirely accurate because of difficulty collecting precise dietary data).
One of the most significant observational studies involved over 6,000 Canadian women between the ages of 25 and 74. The data from the study clearly indicated that women who spent the most time outdoors had a significantly lower risk of developing breast cancer than those who spent the least time outdoors.
In addition, a number of UK studies on the high mortality rate and poor health status in Scotland (known as the "Scottish effect") identified the country's climate and lack of sun as an important factors. 2008 research correlates the generally low level of Vitamin D among the population (roughly four times lower than that of the population in England) with the nation's increased incidence of a number of diseases including cancer and multiple sclerosis.
Laboratory studies also support the Vitamin D deficiency/cancer link, showing that the vitamin both promoted the death of cancer cells and slowed their proliferation. A 2010 State University of New York at Albany study, which included treating human breast cancer cells with a potent form of the vitamin, found that Vitamin D has an effect similar to that of anti-cancer drugs such as Tamoxifen.