Women who are deficient in vitamin D at the time they are diagnosed with breast cancer are nearly 75 percent more likely to die from the disease than women with sufficient vitamin D levels, and their cancer is twice as likely to spread to other parts of the body.

This study links vitamin D with the aggressiveness of disease. A number of prior studies have strongly demonstrated that vitamin D deficiency is associated with an increased risk of developing cancers of the breast, colon, esophagus, pancreas and prostate, and perhaps others. But until now, no study has looked at how vitamin D levels affect the progress of any cancer.

Fifteen percent of the women with healthy vitamin D levels died from their cancer, and 17 percent had their cancers metastasize, or spread to other organs. In contrast, 26 percent of the vitamin D-deficient women died, and 31 percent had cancer that metastasized. This translated into a 73 percent higher risk of death among women who were vitamin D deficient, and a 94 percent higher risk of the cancer spreading..

Vitamin D deficiency was significantly more common among women with a higher body weight. Levels were also lower in younger women which were a bit of a surprise, until we realized older women were taking more supplements.
Women who were premenopausal or had high insulin levels were also more likely to be deficient in vitamin D.

Even with strong evidence that vitamin D can help prevent – and, in the current study, fight off – various cancers, researchers are still unclear on the mechanism by which the chemical works.

- By Harvinder Singh