Does vitamin D protect against breast cancer?

Dr. Santosh Rao is a medical oncologist at Banner MD Anderson Cancer Center in Gilbert.

Question: Does vitamin D protect against breast cancer?

Answer: Low vitamin D levels have been linked to the development of breast cancer. Studies show that women diagnosed with breast cancer have demonstrated low levels of vitamin D, and those with higher levels appear to have a lower risk of developing breast cancer. Women diagnosed with breast cancer that have higher vitamin D levels may also present with smaller tumors, and they appear to have better outcomes. This is especially true in post-menopausal women.

The medical research community recently published a comprehensive meta-analysis of several clinical trials, which studied more than 4,000 women over a decade. The report revealed that women are twice as likely to survive breast cancer if they have vitamin D levels in the highest quintile, compared to women with low levels. The findings also suggest that women should have their vitamin D levels checked regularly to ensure they are maintaining the amount necessary to offer protection against breast cancer. Women who have been diagnosed with breast cancer may benefit from increasing their vitamin D intake to help slow tumor growth and improve their odds of recovery.

Our vitamin D levels are increased by sun exposure, to a lesser extent by diet, and by taking a vitamin D supplement. Although it is easiest to just spend more time in the sun, unfortunately that may increase skin cancer risk. A woman should discuss vitamin D recommendations with her doctor to determine if a vitamin D supplement is needed. Though vitamin D cannot prevent breast cancer on its own nor is it a replacement for breast cancer treatment, research does support its protective benefits for women trying to limit the onset or growth of breast cancer tumors.