Low Vitamin D May Mean Worse Breast Cancer

New research suggests low vitamin D levels may be tied to more agressive forms of breast cancer.

Keeping an Eye on Vitamin D Levels

Today, testing for vitamin D levels is as simple as drawing blood from a patient. A specific blood test known as the 25-hydroxy vitamin D test can quickly and accurately determine whether a patient is vitamin D deficient.

Now that such tests are available, Gralow said that women should be encouraged to stay on top of their vitamin D levels, get screened for their vitamin D levels and safely correct any vitamin D deficiencies with the help of a doctor.

"I wouldn't tell someone not to correct a vitamin D deficiency if they had one," Gralow said. "Finally, in the last year or two, we've developed reliable tests to determine vitamin D levels. There is caution for why we might correct vitamin D levels, such as bone health and calcium absorption, but I don't think if we do it safely that we will create many problems in vitamin D deficiencies."

Until now, only preclinical studies have suggested a link between vitamin D and cancer. Animal studies, as well as epidemiologic data, have suggested that vitamin D deficiencies could affect cancer risk. Moreover, experts have strong biological evidence that vitamin D plays a role in the prevention of colon, prostate and breast cancers.

However, the findings of previous studies on vitamin D and cancer risk have proved conflicting.

A 2006 study by researchers at the University of California at San Diego, involving more than 120,000 women, showed that those women with the highest blood levels of vitamin D had a 50 percent reduced risk of breast cancer. Their study was published in the journal Nutrition Reviews.

However, a 1999 study by researchers at the University of Miami and the Northern California Cancer Center in Union City, Calif., found that vitamin D status had no effect on breast cancer mortality. Their study was published in the Journal of the National Cancer Institute.

Despite the conflicting evidence, some experts still recommend that all their patients supplement their vitamin D.