A study conducted at the Botucatu Medical School of São Paulo State University (FMB-UNESP) found that taking vitamin D may enhance the effectiveness of chemotherapy in women with breast cancer. The research involved 80 women over the age of 45 who were preparing to begin treatment at the university hospital’s oncology outpatient clinic. Participants were divided into two equal groups: one received a daily dose of 2,000 IU of vitamin D, while the other was given a placebo. All patients underwent neoadjuvant chemotherapy aimed at shrinking the tumor before surgery.

After six months, a significant difference was observed between the groups: in the vitamin D group, 43% of women experienced complete tumor disappearance following chemotherapy, compared to 24% in the placebo group. Despite the relatively small sample size, the difference in treatment response was statistically significant. The vitamin D dose used (2,000 IU per day) is much lower than the standard dose typically prescribed to correct deficiencies (usually 50,000 IU per week).

Vitamin D helps the body absorb calcium and phosphorus, which are essential for bone health, and also plays a role in immune system function, including protection against infections and certain diseases such as cancer. Most previous studies on vitamin D and cancer have examined higher doses than those used in this research.

The body primarily produces vitamin D through exposure to sunlight, but it can also be obtained from certain foods. The recommended daily intake is 600 IU for most adults, 800 IU for older adults, and 400 IU for infants. Excessive vitamin D intake can lead to unwanted symptoms such as vomiting, weakness, bone pain, and kidney stones.

At the start of the study, most participants had low blood levels of vitamin D (less than 20 ng/ml). The Brazilian Society of Rheumatology recommends maintaining levels between 40 and 70 ng/ml. Taking the supplement gradually increased vitamin D levels throughout the course of chemotherapy, which may aid in patient recovery. Vitamin D is a more accessible and affordable option compared to some drugs used to boost chemotherapy effectiveness, some of which are not included in Brazil’s national healthcare system.

The study’s results suggest a potential supportive role for vitamin D in cancer treatment, but larger-scale studies are needed to confirm the supplement’s effectiveness and clarify the mechanisms by which it influences the body’s response to chemotherapy. The findings justify further research with a larger number of participants to gain a deeper understanding of how vitamin D may improve chemotherapy outcomes and increase the likelihood of breast cancer remission.