Women with higher vitamin D blood levels have lower risk for breast cancer

Results from a new study published today in PLOS ONE shows women who have higher vitamin D blood levels have a significantly lower risk for breast cancer.

Analyses were done combining data from two randomized trials conducted at Creighton University with data from a cohort from GrassrootsHealth. The combined data included more than 5000 women, aged 55 and older, who had a broad range of vitamin D blood levels.

The study found that those women with a blood level of >60 ng/ml had an 80 percent lower risk for breast cancer than those with levels of 20 ng/ml or less. There was a dose response relationship between blood levels of vitamin D and cancer incidence, i.e. between 20 and 60 ng/mL, the higher the blood vitamin D level, the lower the risk of breast cancer.

Joan M. Lappe, PhD, RN, Criss/Beirne Professor of Nursing and investigator at the Osteoporosis Research Center at Creighton University, was the principal investigator of the two NIH-funded randomized trials conducted at Creighton University that were included in the study.

Lappe's 2007 study on bone health and vitamin D blood levels found, in a secondary analysis, that women who took vitamin D and calcium supplementation for four years had a 60% lower risk of all-type cancer than women who took placebos. In her 2017 study of cancer and vitamin D, she and her team found that women with a vitamin D blood level of 55 ng/ml had a 35 percent significantly lower risk for all-type cancer than those with levels of 30 ng/ml.

Lappe emphasized that having the ability to prevent breast cancer and avoid the suffering endured by breast cancer patients and their families would have a significant impact on the lives of many people.

"This study provides strong support that vitamin D plays an important role in breast cancer prevention," said Lappe. "It also demonstrates that blood levels of vitamin D for breast cancer prevention need to be higher than currently recommended levels for bone health."

The National Academy of Science recommends that having vitamin D blood levels of 20 ng/ml or above is adequate for bone health. In the study reported in PLOS, women with blood levels of 60 ng/ml had a much lower risk of breast cancer than those with levels ≤ 20 ng/ml.

According to Carole Baggerly, a breast cancer survivor and director of GrassrootsHealth, "With roughly an 80 percent reduction in the incidence of breast cancer, getting a vitamin D blood level to 60 ng/ml becomes the first priority for cancer prevention. Nutrition and lifestyle factors are certainly important for overall health, but they can't replace the value of vitamin D level. The safety of this level has been demonstrated within this study as well as others."

Female breast cancer is projected to account for more than 266,000 new cases and 40,900 deaths in the United States in 2018, according to the National Cancer Institute.