Study Shows High-Dose Vitamin D Boosts Treatment Response in Breast Cancer

Low-dose vitamin D supplementation could increase the effectiveness of chemotherapy, according to study investigators from the Botucatu School of Medicine at São Paulo State University (FMB-UNESP) in Brazil. The study authors, who published their findings in the journal Nutrition and Cancer, noted that supplementation with vitamin D could offer an additional treatment option over hard-to-access drugs to increase chemotherapy response.^1,2

Image credit: Galina Zhigalova | stock.adobe.com

“With supplementation, levels increased throughout chemotherapy treatment, which reinforces a possible contribution to the patients’ recovery,” Eduardo Carvalho-Pessoa, president of the São Paulo Regional Brazilian Society of Mastology and one of the authors, said in a news release. “Vitamin D is an accessible and inexpensive option compared to other drugs used to improve the response to chemotherapy.”²

Vitamin D Immunity

Vitamin D is a crucial hormone that supports bone health by facilitating the absorption of calcium and phosphorus, which is obtained mainly from sunlight exposure and food. The recommended daily intake is 600 international units (IU) for individuals who are not vitamin D deficient and 800 IU for older individuals, while babies should receive 400 IU daily as per the American Academy of Pediatrics. Foods including certain fish, egg yolks, and mushrooms are rich in vitamin D and could help reduce or prevent deficiency. However, the study authors noted that it is important to be aware that excessive vitamin D could be toxic, leading to symptoms such as vomiting, weakness, bone pain, and kidney stones.^2,3

Recent research indicates vitamin D’s significant role in bolstering the immune system to combat infections and diseases, including cancer, though most cancer-related studies involved high doses of vitamin D.²

Vitamin D Supplementation With Chemotherapy

To further assess vitamin D’s role in combating diseases, researchers conducted a study to evaluate the effect of vitamin D supplementation on the pathological complete response (pCR) rate in women with breast cancer undergoing neoadjuvant chemotherapy (NCT).¹

A total of 80 women aged 45 and older who were starting treatment at the oncology outpatient clinic of the hospital at FMB-UNESP were included in the randomized clinical trial. The women were divided into 2 groups, and 40 individuals were randomly assigned to receive 2000 IU of vitamin D a day, while the remaining 40 received placebo tablets for a duration of 6 months, with the primary end point of pCR rates.^1,2

Researchers measured 25-hydroxyvitamin-D [25(OH)D] levels in the blood of all included individuals following a breast cancer diagnosis and again at the end of NCT. Of these, 75 women finished NCT and had surgery. Additionally, both groups in the study showed signs of vitamin D deficiency at baseline, with average 25(OH)D levels of 19.6 ± 5.8 ng/mL in the vitamin D group and 21 ± 7.9 ng/mL in the placebo group. However, the study authors noted that this difference was not statistically significant (P= 0.33).^1,2

After 6 months, the vitamin D group demonstrated an increase in 25(OH)D levels to 28 ± 8.7 ng/mL compared to the placebo group's 20.2 ± 6.1 ng/mL (P = 0.03). The primary end point of pCR rate was also notably higher in women who received vitamin D supplementation, at 43%, as opposed to 24% in the placebo group (P = 0.04).^1,2

“Even with a small sample of participants, it was possible to observe a significant difference in the response to chemotherapy. In addition, the dosage [of 2000 IU per day] used in the research is far below the target dose for correcting vitamin D deficiency, which is usually 50,000 IU per week,” Carvalho-Pessoa said in a news release.²

Further results of an adjusted logistic regression analysis revealed that women with 5(OH)D levels of 20 ng/mL or greater were 3.65 times more likely to achieve pCR (odds ratio: 3.65, 95% confidence interval: 1.09-12.8, P = 0.04). Overall, women with breast cancer undergoing NCT who were supplemented with 2000 IU of vitamin D were more likely to achieve a pathological complete response than those in the placebo group.^1,2

“These are encouraging results that justify a new round of studies with a larger number of participants," Carvalho-Pessoa said in the news release. "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.”²

REFERENCES

1. Omodei, M. S., Chimicoviaki, J., Buttros, D. A. B., Almeida-Filho, B. S., Carvalho-Pessoa, C. P., Carvalho-Pessoa, E., … Nahas, E. A. P. (2025). Vitamin D Supplementation Improves Pathological Complete Response in Breast Cancer Patients Undergoing Neoadjuvant Chemotherapy: A Randomized Clinical Trial. Nutrition and Cancer, 77(6), 648–657. Accessed June 13, 2025. doi.org/10.1080/01635581.2025.2480854

2. Vitamin D increases the likelihood that breast cancer will disappear with chemotherapy. EuerkAlert!. News release. June 12, 2025. Accessed June 13, 2025. https://www.eurekalert.org/news-releases/1087283

3. 7 Nutritious Foods That Are High in Vitamin D. Healthline. News release. Updated April 7, 2025. Accessed June 13, 2025. https://www.healthline.com/nutrition/9-foods-high-in-vitamin-d