Higher blood levels of vitamin D may be associated with improved survival from breast cancer, suggest new findings from study published this week in Anticancer Research.
The study, a meta-analysis of 5 studies of vitamin D (25-hydroxyvitamin D) serum concentrations obtained at the time of breast cancer diagnosis, involved a total of 4443 women who were followed-up for an average of 9 years. The women were divided into quintiles of vitamin D serum concentrations. Women in the highest vitamin D quintile (an average of 30 ng/mL) were about half as likely to die of breast cancer during the follow-up period as those in the lowest quintile (an average of 17 ng/mL), the researchers found.
There’s a biologically plausible mechanism for vitamin D’s apparent beneficial effect on breast cancer survival, the authors suggest. “Vitamin D metabolites increase communication between cells by switching on a protein that blocks aggressive cell division,” said Cedric F. Garland, DrPH, a coauthor of the study and professor in the department of Family and Preventive Medicine, University of California, San Diego School of Medicine, in a statement. As long as vitamin D receptors are present on the tumor cells (where they remain until the tumor is advanced), “tumor growth is prevented and kept from expanding its blood supply,” he explained. “This is the reason for better survival in patients whose vitamin D blood levels are high.”
Although the researchers did not study whether adding vitamin D supplements to the diet of women diagnosed with breast cancer improved survival, they did recommend such supplementation to get serum vitamin D levels into the normal range, which is between 30 ng/mL and 74 ng/mL.
Breast cancer is the most common cancer in women worldwide, with about 1.7 million new cases and a half million deaths reported in 2012. In the United States, about 234 600 new cases and about 40 000 deaths from breast cancer were reported in 2013.