Vitamin D increases the likelihood that breast cancer will disappear with chemotherapy

In a study conducted at São Paulo State University with 80 women over the age of 45, low-dose vitamin D supplementation nearly doubled the treatment response rate.

By Maria Fernanda Ziegler  |  Agência FAPESP – A study conducted at the Botucatu School of Medicine at São Paulo State University (FMB-UNESP) in Brazil has shown that low-dose vitamin D supplementation can increase the effectiveness of chemotherapy treatment in women with breast cancer. The results suggest that the substance could be an alternative to hard-to-access drugs that also aim to increase the response to chemotherapy.

The research, supported by FAPESP, involved 80 women over the age of 45 who were about to start treatment at the oncology outpatient clinic of the general and teaching hospital (“Hospital das Clínicas”) at FMB-UNESP. They were separated into two groups: 40 of them took 2,000 IU (international units) of vitamin D a day, while the other 40 received placebo tablets. 

After six months of cancer treatment and supplementation, 43% of participants using vitamin D saw their disease disappear with the use of chemotherapy, compared to 24% of the placebo group. All the participants in the study underwent so-called neoadjuvant chemotherapy, which is used to facilitate surgery to remove the tumor. 

“Even with a small sample of participants, it was possible to observe a significant difference in the response to chemotherapy. In addition, the dosage used in the research [2,000 IU per day] is far below the target dose for correcting vitamin D deficiency, which is usually 50,000 IU per week,” says Eduardo Carvalho-Pessoa, president of the São Paulo Regional Brazilian Society of Mastology and one of the authors of the article published in the journal Nutrition and Cancer. 

Immunity

Vitamin D is a hormone that aids in the absorption of calcium and phosphorus, which is essential for bone health. Recent studies have shown that it also plays an important role in the immune system by helping to fight infections and diseases, including cancer. However, most studies linking cancer and vitamin D supplementation have used high doses of the substance.

This hormone is obtained primarily through exposure to sunlight and food. The recommended daily intake is 600 IU for those who are not deficient in the vitamin, and 800 IU a day for older people. The American Academy of Pediatrics recommends 400 IU of vitamin D per day for babies. It is important to note that too much can be toxic and cause vomiting, weakness, bone pain, and kidney stones.  

Most of the participants in the study had low levels of vitamin D, defined as less than 20 nanograms per milliliter (ng/mL) of blood. The Brazilian Society of Rheumatology recommends levels between 40 and 70 ng/mL. “With supplementation, levels increased throughout chemotherapy treatment, which reinforces a possible contribution to the patients’ recovery,” Carvalho-Pessoa told Agência FAPESP. “Vitamin D is an accessible and inexpensive option compared to other drugs used to improve the response to chemotherapy, some of which are not even included in the list of the Unified Health System [the Brazilian national public health network, known as the SUS, its acronym in Portuguese],” he adds. 

For the researcher, the findings pave the way for further investigation into the auxiliary role of the substance in the response to cancer treatment. “These are encouraging results that justify a new round of studies with a larger number of participants. This will allow a greater understanding of the role of vitamin D in increasing the response to chemotherapy treatment and, consequently, in the greater likelihood of breast cancer remission,” he concludes.

The article “Vitamin D Supplementation Improves Pathological Complete Response in Breast Cancer Patients Undergoing Neoadjuvant Chemotherapy: A Randomized Clinical Trial” can be read at: www.tandfonline.com/doi/full/10.1080/01635581.2025.2480854.