Low Vitamin D Levels Raise Breast Cancer Death Risk by 75 Percent

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," said JoEllen Walsh of the University of Albany, who was not involved in the study. "It suggests that your vitamin D status may affect how your disease progresses."

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.

Between 1989 and 1995, researchers tested the blood of 512 women who had been newly diagnosed with breast cancer. All the breast cancer cases were localized, meaning the disease had not spread beyond the breast and armpit region. The average participant age was 50.

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.

Among a third group of women, classified as not deficient in the vitamin but still falling short of optimal blood levels, there was no difference in cancer death rates.

Vitamin D deficiency was significantly more common among women with a higher body weight. According to study author Pamela Goodwin of Mount Sinai Hospital and the University of Toronto, this is because "fat tissue acts as a trap for vitamin D."
"Levels were also lower in younger women," she said, "which was 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.

Only 24 percent of the women involved in the study had vitamin D levels considered healthy, while 37.5 percent were considered deficient and the remaining 38.5 percent fell in between.

"This study found that vitamin D deficiency is very common among women with breast cancer, and it suggests that vitamin D deficiency is linked to poorer outcomes in these women," said Nancy Davidson, director of the breast cancer program at the Johns Hopkins Kimmel Cancer Center and president of the American Society of Clinical Oncology.

Goodwin recommended that women who are diagnosed with breast cancer should take a simple blood test to determine their body's vitamin D levels.

"If you're a woman with breast cancer, it's probably worthwhile having vitamin D levels checked. If they're deficient, they should take more to get it in the range that we think is beneficial," she said. "This study is significant because it tells us this may be one thing women can do to improve their prognosis," said Anne McTiernan of the Fred Hutchinson Cancer Research Center.

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.
"We know from basic science studies that breast cancer cells have vitamin D receptors and can interact with vitamin D," Goodwin said.
Some scientists have suggested that the nutrient might play a role in regulating programmed cell death, without which cells can turn cancerous.
"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," Walsh said. "The effects of vitamin D on breast cancer cells are very similar to the established drug Tamoxifen that many women take for breast cancer."
In a demonstration for ABC News, Walsh added vitamin D to a breast cancer culture, causing the cells to shrivel up and die.
Breast cancer cells are not the only cells with vitamin D receptors. In fact, nearly every cell in the body interacts with the vitamin in some way.
Vitamin D, technically a hormone, is synthesized by the body upon exposure to ultraviolet radiation from sunlight. It can also be acquired from certain dietary sources, including grains and dairy, which are fortified with it in many countries, or via supplements.
The average light-skinned person can produce all the vitamin D he needs from about 15 minutes a day of sunlight on the face and hands, while it takes about twice as long for a darker skinned person. But at far northern latitudes, especially during the winter, there may not be enough sunlight for the body to produce sufficient quantities.
Daily vitamin D recommendations vary widely by country, with the United States and Canada recommending 200 IU per day for children and 400 IU for adults. But many researchers, and even the Canadian Cancer Society, have recommended that this value be raised to 1,000 IU per day. While 400 IU may be sufficient to maintain bone health, scientists say, higher levels are needed to provide cancer-fighting benefits.