High-Dose Vitamin D Enhances Chemotherapy Efficacy in Breast Cancer Patients

A recent study conducted by researchers at the Botucatu School of Medicine at São Paulo State University (FMB-UNESP) in Brazil has revealed promising findings regarding the role of high-dose vitamin D in enhancing the effectiveness of chemotherapy for breast cancer patients. Published in the journal *Nutrition and Cancer* on June 12, 2025, the study indicates that vitamin D supplementation significantly boosts the pathological complete response (pCR) rates in women undergoing neoadjuvant chemotherapy (NCT).

The research involved 80 women aged 45 and older who were receiving treatment at the oncology outpatient clinic at FMB-UNESP. Participants were randomly assigned to either a vitamin D supplementation group, receiving 2000 International Units (IU) of vitamin D daily, or a placebo group for a duration of six months. The primary endpoint measured was the rate of pCR, defined as the absence of detectable cancer in breast tissue following chemotherapy.

According to Dr. Eduardo Carvalho-Pessoa, president of the São Paulo Regional Brazilian Society of Mastology and one of the study's authors, “With supplementation, levels increased throughout chemotherapy treatment, which reinforces a possible contribution to the patients’ recovery. Vitamin D is an accessible and inexpensive option compared to other drugs used to improve the response to chemotherapy.” In the vitamin D group, the average 25-hydroxyvitamin D [25(OH)D] level increased from 19.6 ng/mL at baseline to 28 ng/mL at the end of the treatment, while the placebo group only reached 20.2 ng/mL.

The results indicated a pCR rate of 43% in the vitamin D group compared to 24% in the placebo group, a statistically significant difference (P = 0.04). Furthermore, logistic regression analysis revealed that women with 25(OH)D levels of 20 ng/mL or higher were 3.65 times more likely to achieve pCR (odds ratio: 3.65, 95% confidence interval: 1.09-12.8, P = 0.04).

Despite the study's promising outcomes, experts caution against excessive vitamin D intake, which can lead to toxicity. Dr. Carvalho-Pessoa emphasized the need for further studies with larger participant groups to validate these findings and explore the role of vitamin D in increasing chemotherapy response and enhancing breast cancer remission rates.

Vitamin D is known for its critical role in immune support, bone health, and calcium absorption. The American Academy of Pediatrics recommends a daily intake of 600 IU for individuals without deficiency and 800 IU for older adults. Natural sources of vitamin D include fish, egg yolks, and fortified foods. The findings of this study highlight the potential of integrating vitamin D supplementation into standard breast cancer treatment protocols, offering a less invasive and cost-effective option for patients.

As the medical community continues to search for effective strategies to improve chemotherapy outcomes, the implications of this research could lead to significant changes in treatment approaches for breast cancer, particularly in developing regions or for patients with limited access to expensive therapeutic options.