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May 17, 2011

Vitamin D linked to breast tumor progression, blood pressure

Aggressive breast tumors linked to vitamin D deficiency

Low vitamin D levels among women with breast cancer correlate with more aggressive tumors and poorer prognosis, according to a new Medical Center study highlighted at the American Society of Breast Surgeons meeting in Washington, D.C.

The study is one of the first to examine vitamin D and breast cancer progression. Previous research has focused on vitamin D deficiency and the risk of cancer development. The Medical Center epidemiology study associates suboptimal vitamin D levels with poor scores on every major biological marker that helps physicians predict a patient’s breast cancer outcome.

“The magnitude of the findings was quite surprising,” says lead researcher Luke Peppone, a research assistant professor of Radiation Oncology at the Wilmot Cancer Center. “Based on these results, doctors should strongly consider monitoring vitamin D levels among breast cancer patients and correcting them as needed.”

Peppone and senior investigator Kristin Skinner, an associate professor of surgery and director of the Wilmot Comprehensive Breast Care Center, examined prognostic factors for 155 women who underwent surgery for breast cancer between January 2009 and September 2010. They also obtained blood tests that provided vitamin D status for all the patients within the one-year period before or after surgery.

Meanwhile, researchers collected relevant breast cancer data on each patient, including age, race, menopause status, stage of cancer at diagnosis, estrogen and progesterone status, HER2 expression, gene expression, and Oncotype Dx score. The Oncotype is a newer diagnostic test for early-stage breast cancer that looks at a group of 21 genes within a woman’s tumor sample and issues a score between 0 and 100 that correlates with the likelihood of a recurrence. A higher risk of recurrence is usually reflected in scores greater than 30.

A statistical analysis showed that cancers known to be more aggressive, such as triple-negative tumors, correlated with low vitamin D levels. Triple-negative cancers are often associated with younger women and minority women, and Peppone’s study also found that both premenopausal women and black women tended to have suboptimal vitamin D levels, compared to older, Caucasian women.

A growing number of physicians are already monitoring cancer patients and healthy people for vitamin D. Last fall the Institute of Medicine announced new daily recommended intakes of vitamin D for nearly all adults and children in the United States and Canada. Although the institute did not specifically address vitamin D and cancer, it reported that 600 IUs daily meets the needs of most people. Higher amounts are often prescribed to cancer patients; sometimes a weekly dose of 50,000 IUs is necessary to treat severely deficient people.

Further research is needed to explore the biological basis of the relationship between D and tumor markers, but Peppone says his study highlights the importance of obtaining vitamin D levels in women diagnosed with breast cancer.

Vitamin D may help explain racial differences in blood pressure

High blood pressure, or hypertension, is more common and often more deadly in blacks than in whites, and a new Medical Center study shows that low vitamin D levels among black people might be a powerful factor that contributes to the racial differences in hypertension.

The findings, published online in the Journal of General Internal Medicine, are consistent with growing evidence that lower vitamin D status is associated with higher blood pressure, and that people with darker skin generally produce less vitamin D.

“Our study confirms that vitamin D represents one piece of the complex puzzle of race and blood pressure,” says lead author Kevin Fiscella, a professor of family medicine. “And, since black-white differences in blood pressure represent thousands of excess deaths due to heart disease and stroke among blacks, we believe that simple interventions such as taking vitamin D supplements might have a positive impact on racial disparities.”

Fiscella and colleagues analyzed data from the National Health and Nutrition Examination Survey, 2001–06. Their sample included nearly 2,000 blacks and approximately 5,100 non-Hispanic whites, ages 20 and older. Researchers specifically compared the average systolic pressure and blood levels of vitamin D among the study participants.

Most vitamin D is produced by the skin in response to sunlight and metabolized in the liver where it is converted to 25 hydroxyvitamin D or 25(OH) D, the form used to determine a person’s vitamin D status through a blood test. Deficiency is usually defined as less than 20 nanograms per milliliter; lower than 15 ng/ml is inadequate to maintain bone health and normal calcium metabolism.

Many people around the world have low concentrations of vitamin D. Genetic factors common to blacks, such as darker skin, reduce vitamin D synthesis. In addition, a higher incidence of lactose intolerance among blacks, which can eliminate vitamin-D fortified milk from the diet, contributes to lower dietary intake, previous research has shown.

Notably in Fiscella’s data, 61 percent of blacks compared to 11 percent of whites had vitamin D levels in the lowest one-fifth of the population sample, whereas only 2 percent of blacks compared to 25 percent of whites had vitamin D levels in the highest group.

However, Fiscella notes some limitations to the study and said that vitamin D did not fully explain the racial differences in blood pressure. “It is likely that other factors beyond vitamin D, such as psychological stress, medication adherence, and discrimination could contribute to this disparity,” he wrote in the article. “Further study using more refined measures of skin color is needed to tease apart the complex relationship between skin type, stress, vitamin D, and hypertension.”

The National Heart Lung and Blood Institute funded the research.

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