Elevated vitamin D levels reduced breast cancer mortality risk by half

Breast cancer patients with high blood concentrations of vitamin D have twice the likelihood of survival than women who are vitamin D insufficient, according to results of a meta-analysis.

“Vitamin D metabolites increase communication between cells by switching on a protein that blocks aggressive cell division,” Cedric F. Garland, DrPH, professor in the department of family and preventive medicine at University of California, San Diego, School of Medicine, said in a press release. “As long as vitamin D receptors are present, tumor growth is prevented and kept from expanding its blood supply. Vitamin D receptors are not lost until a tumor is very advanced. This is the reason for better survival in patients whose vitamin D blood levels are high.”

Garland and colleagues conducted a literature search to identify five studies that included HRs for mortality from breast cancer, stratified by quantiles of blood 25-hydroxyvitamin D levels. The studies included a combined patient population of 4,443 women, with an average follow-up of 9 years.

Researchers used a random-effects model to calculate a pooled HR, and the DerSimonian-Laird test was applied to evaluate homogeneity of the studies.

Researchers observed lower case-fatality rates after breast cancer diagnosis among patients with higher blood levels of 25-hydroxyvitamin D. Notably, patients in the highest category of 25-hydroxyvitamin D concentration had roughly half the fatality rate from breast cancer vs. those in the lowest (HR=0.56; 97% CI, 0.4-0.7).

Women in the highest category had an average 25-hydroxyvitamin D serum level of 30 ng/mL, whereas those in the low group averaged 17 ng/mL.

Individuals who consume 4,000 IU/day vitamin D would typically achieve a blood level of 50 ng/mL, according to investigators.

“There is no compelling reason to wait for further studies to incorporate vitamin D supplements into standard care regimens, since a safe dose of vitamin D needed to achieve high serum levels above 30 nanograms per milliliter has already been established,” Garland said.

Disclosure: The research was supported by a congressional allocation to the Penn State Cancer Institute of the Milton S. Hershey Medical Center in Hershey, Pa., through the Department of the Navy, Bureau of Medicine and Surgery.