A new prospective study has reported that there is no relationship between circulating vitamin D levels and recurrence of breast cancer. The study was designed to investigate the relationships between blood levels of vitamin D (as determined by 25-hydroxyvitamin D (25(OH)D) concentrations) and vitamin D intake and breast cancer recurrence after treatment. The study included 3,085 women within the Women's Healthy Eating and Living Study for whom circulating concentrations of 25(OH)D and dietary, supplemental, and total intake of vitamin D were assessed. Associations were calculated for recurrent or new breast cancer events. In addition, a nested study with 512 matched pairs was used to analyze the associations between 25(OH)D levels and breast cancer recurrence.

No associations were found between circulating 25(OH)D levels and recurrence. The authors found no statistically significant differences between breast cancer rates of women with serum concentrations of 25(OH)D of at least 30 ng/mL and those with concentrations under 10 ng/mL or levels in between. Levels below 30 ng/mL are considered deficient by many observers, although there is less agreement on what constitutes an optimal level of circulating vitamin D. No significant associations were found when the analyses were conducted according to menopausal status or different types of recurrences (local, regional, or distant recurrence or death). However, the analysis was hampered somewhat by a relatively small number of premenopausal women and women with 25(OH)D concentrations of less than 10 ng/mL among the 512 matched pairs. When considering intake of vitamin D (rather than circulating 25(OH)D levels), total intake (through diet and supplements) was not found to be related to breast cancer recurrence overall. However, dietary vitamin D intake was found to be protective against recurrence among premenopausal women.

Please see our article on vitamin D for an in depth discussion of the relationship between vitamin D and breast cancer.