Vitamin D and Breast Cancer

Adequate serum levels of Vitamin D have been associated with decreased risk of several cancers, including breast cancer. Why? Some studies have shown vitamin D inhibits the formation of malignant breast cells. Regardless of the mechanism, KD Crew and associates recently published an abstract on line that indicates vitamin D levels are inversely related to breast cancer risk.

This population-based, case-controlled study compared vitamin D plasma levels of 1,026 women diagnosed with breast cancer between 1996 and 1997 with vitamin D plasma levels of 1,075 women who lived in the same area of Long Island, New York.

The authors found:

• Plasma vitamin D levels were inversely related to breast cancer risk


• All women with vitamin D levels greater than or equal to 40 ng/mL were 46% less likely to have breast cancer than women with vitamin D levels less than 20 ng/mL


• Postmenopausal women benefited most with a 54% reduction of breast cancer risk if their serum vitamin D level was greater than or equal to 40 ng/mL

These results add to a growing body of evidence that adequate vitamin D stores may prevent breast cancer development. It is known that circulating vitamin D levels of more than 32 ng/mL are associated with normal bone mineral metabolism; this data suggest that the optimal level for breast cancer prevention is greater than or equal to 40 ng/mL. More clinical trials are urgently needed to evaluate the role of vitamin D supplementation on breast cancer prevention.

What I tell my patients

It is unknown, as of yet, the optimal plasma level of 25-hydroxyvitamin D. Evidence continues to mount that our previous perception of "normal" levels of vitamin D falls short. Many experts now believe that a range of 40 to 80 ng/mL is an optimal range to protect us from many chronic and debilitating illness. However, many labs still report a 25-hydroxyvitamin D level as "normal" when it falls in the range of 20 - 100 ng/mL. Have your levels tested. Ask your doctor what your 25-hydroxyvitamin D level is. I recommend a level of 52 - 80 ng/mL to my patients (colon cancer risk is cut in half at 52 ng/mL).

Do self-breast exams monthly. Get annual mammograms starting at age forty; sooner if advised. Get 20 minutes of sunshine (without sun block) at least 3 days per week. Eat a diet abundant in vegetables, fruit, whole grains and omega-3's. Eat organic, when possible. Exercise regularly. Limit alcohol consumption to no more than 1 drink per day. Laugh often. Enjoy nature. Practice silence. And, be your own best health advocate.

Reference: Crew KD, et al. Association between Plasma 25-Hydroxyvitamin D and Breast Cancer Risk. Cancer Prev Res (Phila Pa). 2009 May 26. [Epub ahead of print]