Video: Study: Vitamin D deficiency may increase risk for breast cancer

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The evidence continues to pour in about vitamin D. Deficiencies may be linked to back pain in older women and may increase the risk for breast cancer. The newest study suggests the farther you live from the equator, the greater the risk.

Vitamin D is normally associated with strong bones, but new research indicates it may also play a crucial role in breast cancer.

"We need to be more aware of vitamin D levels," said Dr. Jennifer Ligibel, oncologist, Dana Farber Cancer Institute.

A study of 500 women with breast cancer found three-quarters had a vitamin D deficiency upon diagnosis, and that deficit appeared to increase the risk of the cancer spreading and death significantly. Experts say while adequate levels of vitamin D are important, don't stock up on the supplement just yet.

"It doesn't really prove that vitamin D itself is what's causing the breast cancer or what's making the breast cancer come back," said Ligibel.

A separate study from the Mayo Clinic finds mastectomy rates are up 13 percent among women with early stage breast cancer. The use of new MRI technology may have played a role.

"There's been an enormous growth in use of MRI, and I think that until this study we really haven't known what the consequences of that have been," said Ligibel.

The study showed more than half of patients who had an MRI also had a mastectomy, while just under 40 percent without the scan had the surgery. Identifying previously unseen cancers is a good thing, but studies have yet to prove mastectomy is the new gold standard.

"Women who had a mastectomy, so removing all the breast tissue, had the same long-term survival rates as women who had just the tumor removed and then also received radiation," said Ligibel.

There are also studies planned to determine whether mastectomy can improve a woman's chance of beating the disease long-term.

Another observational study on vitamin D and breast cancer is under way and more rigorous studies are in the works.