Researchers have found that breast cancer patients who don't have enough vitamin D in their bodies are much more likely to have their cancer spread and to die from the disease.
For millions of women, the finding in a new study raises the possibility that a basic nutrient like vitamin D, a vitamin pill that costs just pennies a day, might have a profound impact on their breast cancer.
Dr. Anne McTiernan at the Fred Hutchinson Cancer Research Center said, "This study is significant because it tells us this may be one thing women can do to improve their prognosis."
Researchers, following more than 500 women with breast cancer, found that women deficient in vitamin D were 94 percent more likely to have their cancer spread and 73 percent more likely to die from their cancer.
JoEllen Welsh, a professor at the State University of New York at Albany, said, "Vitamin D is pretty unique in its action in that it does enter the cancer cells and induces them to undergo a cell death process."
Welsh should know. She studies vitamin D in her laboratory. Under a microscope, she showed ABC News a cluster of human breast cancer cells that shriveled up and died when she added vitamin D.
"The effects of vitamin D on breast cancer cells are very similar to the established drug Tamoxifen that many women take for breast cancer."
Vitamin D, essential for strong bones, has also been linked in several studies with cancer prevention. And not only breast cancer but colon and prostate cancers as well.
The problem, said cancer researchers, is that many women and men are not getting enough vitamin D. In this latest study, 76 percent of the breast cancer patients had low levels of the nutrient.
A simple blood test can determine whether someone is vitamin D deficient and by how much.
McTiernan, a researcher in breast cancer prevention, exercises daily, eats nutritiously and recently discovered that she too had dangerously low levels of the nutrient.
"I was very surprised at how low my vitamin D levels were. I thought I was doing everything right." she said.
Now with daily vitamin D supplements, she just might be.
For more information on vitamin D, check out the fact sheet provided by the National Institues of Health here.