Vitamin D May Help Protect Women From Aggressive Breast Cancer

By Michelle Fay Cortez

May 16 (Bloomberg) -- Vitamin D, a byproduct of sunlight and a supplement in milk, may help protect women from deadly breast cancer, a study found.

Women with low levels of vitamin D in their blood when they were diagnosed with cancer were 94 percent more likely to have the disease spread and 73 percent more likely to die from it a decade later than those with recommended levels of the vitamin, researchers said. More than three of every four women had low levels of the vitamin when they learned they had breast cancer, according to the study to be presented at the American Society of Clinical Oncology conference.

Sunshine is the greatest source of vitamin D, produced when ultraviolet light strikes the skin. Studies have shown vitamin D, which occurs naturally in few foods, may make several types of cancer less lethal and protect against breast cancer, the most common malignancy in women. The latest findings suggest women who don't get enough of it may be most vulnerable.

``There is growing evidence that there is an optimal range of vitamin D for a wide range of health outcomes,'' said Pamela Goodwin, the lead author of the study and professor of medicine at the University of Toronto. ``We've shown that vitamin D deficiency is common at breast cancer diagnosis, it's associated with higher grade tumors and it's associated with an increased risk of distant recurrence and death.''

Death, Sunscreen

More than 180,000 women will be diagnosed with breast cancer in the U.S. this year and nearly 41,000 will die, according to the American Cancer Society. It's the most common cancer in women and the second-most deadly after lung cancer. Meanwhile, public health efforts to keep people out of the sun and to use sunscreen as a way to lower risks of skin cancer have lowered vitamin D levels, studies show.

The data was reported at an online briefing by ASCO, one of the nation's largest cancer organizations. The findings will be presented at ASCO's annual meeting at the end of May.

The study doesn't prove that a lack of vitamin D caused cancer to become more aggressive, just that a deficiency and deadly tumors were often linked, Goodwin said. More studies are needed to confirm the findings and to determine whether giving vitamin supplements to women with breast cancer will improve their prognosis, she said at a news conference yesterday.

Too Compelling?

``My concern as it relates to breast cancer risk is women will avoid other ways to maintain breast health if they feel the evidence is so compelling that vitamin D reduces risk that they avoid screening mammograms and all the other general health things that they should be doing,'' she said.

The study, funded by the Breast Cancer Research Foundation, included 512 women with an average age of 50 who were followed for more than a decade after they were diagnosed between 1989 and 1995 at University of Toronto hospitals.

Those with low vitamin D levels also ate few grains and drank little alcohol. The deficiency was also more common in younger, overweight women with advanced tumors. Adjusting for those things didn't change the results, the researchers said.

After a decade, 26 percent of women with a vitamin D deficiency died from the disease, compared with 15 percent of those who had adequate levels, the study found. The disease progressed or metastasized in 31 percent of those with a deficiency and 17 percent of those with enough of the vitamin.

The findings may lead more women to get tested for vitamin D deficiency and to correct low levels, said Julie Gralow, chair of ASCO's cancer communications committee and associate professor at the University of Washington.

First Study

``This is the first study to really suggest an association between vitamin D deficiency and the outcome after a diagnosis of breast cancer, the relapse or the death,'' Gralow said on the conference call. ``I wouldn't tell someone not to correct their vitamin D if they knew they had a deficiency,'' she said.

Still, she emphasized that researchers have no idea whether correcting those levels will improve the women's fate. It may be that the deficiency leads to higher-risk cancers, and fixing the problem later won't change the results, she said.

In addition, the study suggested that women whose vitamin D level is too high may have an increased risk of death, though the results weren't conclusive.

``We now have a tool to evaluate vitamin D in the blood and we should begin to use it more'' Goodwin said.

To contact the reporter on this story: Michelle Fay Cortez in Minneapolis at mcortez@bloomberg.net

Last Updated: May 16, 2008 00:01 EDT

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