Scientists Discover Unexpected Connection Between Vitamin D Levels and Pain Severity

A simple vitamin deficiency may be making recovery from breast cancer surgery far more painful than expected. New research suggests women with low vitamin D levels experience more postoperative pain and require substantially higher amounts of opioid medication after mastectomy surgery.

The study, published in Regional Anesthesia & Pain Medicine, found that breast cancer patients deficient in vitamin D were three times more likely to experience moderate to severe pain during the first 24 hours after surgery compared with women who had healthier vitamin D levels.

Researchers conducted the prospective study at Fayoum University Hospital between September 2024 and April 2025. The study included 184 women undergoing unilateral modified radical mastectomy for breast cancer. Half of the participants had vitamin D deficiency, defined as levels below 30 nmol/L.

Doctors and nurses treating the patients were unaware of their vitamin D status. All women received the same standard pain management during and after surgery, including fentanyl during the operation and patient-controlled tramadol afterward.

The differences in pain medication use were striking. Women with low vitamin D required slightly more fentanyl during surgery, but after surgery they used an average of 112 milligrams more tramadol than patients with sufficient vitamin D levels.

Researchers believe vitamin D may influence pain sensitivity through its effects on inflammation and immune system regulation. Previous studies have already linked vitamin D deficiency to chronic pain conditions, and deficiency is also common among breast cancer patients.

The study also found that nausea after surgery occurred more frequently in women with low vitamin D levels. Vomiting was only reported in the deficient group, although the numbers were too small to confirm a statistically significant difference.

While the researchers emphasized that the study cannot prove vitamin D deficiency directly caused worse pain outcomes, the findings raise the possibility that correcting low vitamin D before surgery could help improve recovery and reduce opioid dependence after breast cancer procedures.

REFERENCE: Mahdy Ahmed Abdelhady, Maged Labib Boulos, Mohamed Ahmed Hamed, Doha Hamad Masry, Safaa Gaber Ragab, Mohamed Hasan Ragab. Association between preoperative vitamin D level and postoperative pain in patients undergoing breast cancer surgery: a prospective observational study. Regional Anesthesia, 2026; rapm-2025-107495 DOI: 10.1136/rapm-2025-107495