Low serum levels of vitamin D have been reported as a risk factor for breast cancer. This
narrative review provides an update on the impact of vitamin D on hormone receptors, notably
estrogen receptor subunits, and gives insights on possible therapeutic interventions to overcome
breast cancer. In addition, evidence that supports the beneficial use of vitamin D as adjuvant
treatment of breast cancer is summarized. Vitamin D deficiency is significantly widespread in
patients with triple-negative tumors. Several studies have observed a possible modulatory effect
of vitamin D or its analogues on the expression of different hormone receptors in breast cancer
and increased sensitivity to tamoxifen. Vitamin D possesses anti-inflammatory and immunomodulatory
effects in patients with breast cancer, and the mechanism of action of vitamin D in patients
with breast cancer is discussed. In conclusion, vitamin D appears to have a beneficial role in the
prevention and management of breast cancer, however, large-scale, randomized controlled trials
are needed to confirm the effects of vitamin D in breast cancer prevention or treatment.