New Study Highlights Potential Role of Vitamin D in Breast Cancer Care

A low-cost vitamin sitting on pharmacy shelves may quietly boost one of cancer care's most powerful tools-chemotherapy. A new study from Sao Paulo State University suggests that Vitamin D supplementation could significantly improve treatment response in women with breast cancer.

Conducted at the Botucatu School of Medicine and published in the journal Nutrition and Cancer, the study followed 80 women over 45 undergoing neoadjuvant chemotherapy—treatment given before surgery to shrink tumors. Participants were split into two groups: one received a daily dose of 2,000 IU of vitamin D, while the other received a placebo.

After six months, the difference was striking. About 43% of women taking vitamin D experienced complete disappearance of their tumors, compared to 24% in the placebo group.

Vitamin D is widely known for its role in bone health, but it also plays a key part in immune function. Researchers believe this immune-modulating effect may help the body better respond to cancer treatment. Notably, most participants in the study started with low vitamin D levels, which increased during supplementation—suggesting a possible link between improved levels and better outcomes.

Another important takeaway is accessibility. Compared to expensive drugs designed to enhance chemotherapy response, vitamin D is inexpensive and widely available, making it a potentially valuable addition to treatment—especially in resource-limited settings.

However, experts urge caution. These findings are promising but preliminary. Larger clinical trials are needed to confirm the benefits and understand exactly how vitamin D interacts with chemotherapy at a biological level. It’s also important not to self-prescribe high doses, as excessive intake can lead to side effects like kidney stones and weakness.

For now, the study opens the door to a simple yet powerful idea: sometimes, small nutritional interventions could make a meaningful difference in complex diseases like cancer.

REFERENCE: Michelle Sako Omodei, Jackeline Chimicoviaki, Daniel Araujo Brito Buttros, Benedito Souza Almeida-Filho, Carla Priscila Carvalho-Pessoa, Eduardo Carvalho-Pessoa, Heloisa De Luca Vespoli, Eliana Aguiar Petri Nahas. Vitamin D Supplementation Improves Pathological Complete Response in Breast Cancer Patients Undergoing Neoadjuvant Chemotherapy: A Randomized Clinical Trial. Nutrition and Cancer, 2025; 77 (6): 648 DOI: 10.1080/01635581.2025.2480854