Low vitamin D levels before breast cancer surgery may be linked to more pain during recovery, according to a new study.
The research, published in Regional Anesthesia & Pain Medicine, found that breast cancer patients with vitamin D deficiency were more likely to report moderate pain in the first 24 hours after a radical mastectomy and used more opioid medication after surgery. The study was observational, meaning it cannot prove that low vitamin D caused more pain or that supplements before surgery would improve recovery.
Vitamin D is best known for its role in bone health, but researchers are also studying how it may affect inflammation, immune function and how the body processes pain. Vitamin D deficiency is also commonly reported among people with breast cancer, making it a possible factor to examine before surgery.
For the study, researchers followed 184 breast cancer patients at Fayoum University Hospital in Egypt between September 2024 and April 2025. All were scheduled to undergo unilateral modified radical mastectomy, a surgery to remove one breast.
Half of the patients had vitamin D deficiency, defined as levels below 30 nmol/L. The other half had vitamin D levels above that threshold. The two groups had similar average ages, 44 in the deficient group and 42 in the sufficient group.
Patients were treated according to the hospital’s usual surgery and pain-control protocols. The clinical staff caring for them did not know their vitamin D status.
During surgery, patients received fentanyl to manage acute pain. After surgery, all patients received paracetamol through an IV every eight hours. They also had access to patient-controlled tramadol, an opioid pain medication, meaning they could press a button to receive medication within set limits.
Researchers recorded pain levels immediately after surgery and again at six, 12, 18 and 24 hours. They also tracked nausea, vomiting, sedation and length of hospital stay.
Patients with vitamin D deficiency were three times more likely to report moderate to severe postoperative pain at some point during the first 24 hours than those with sufficient vitamin D levels. However, no patients in either group reported severe pain, defined as 7 or higher on a 0-to-10 scale. The difference was driven by moderate pain, which was defined as 4 to 6 on the scale.
The deficient group also used more pain medication. During surgery, they received an average of 8 micrograms more fentanyl, a difference the researchers described as modest. After surgery, they used substantially more tramadol, averaging 112 milligrams compared with patients who had sufficient vitamin D levels.
Nausea was also more common among patients with vitamin D deficiency, and vomiting occurred only in that group. However, the difference in vomiting was small and was not statistically significant.
The findings suggest vitamin D status may be worth studying as part of preoperative planning for breast cancer patients, especially because opioid medications can cause side effects such as nausea, vomiting, drowsiness and confusion and carry risks of dependency.
The study does not show whether correcting vitamin D deficiency before surgery would reduce pain or opioid use. The researchers did not test supplementation, and they did not collect information on several factors that could affect pain, including anxiety, depression, sleep disturbance, cancer stage or prior cancer treatment. They also did not measure inflammatory markers, so they could not directly study why vitamin D might be linked to pain.
The authors concluded that vitamin D deficiency was associated with more moderate to severe postoperative pain and increased opioid consumption among patients undergoing unilateral modified radical mastectomy. They also suggested that preoperative vitamin D supplementation in breast cancer patients with levels below 30 nmol/L may have a role in modulating postoperative pain.
For now, the findings are best understood as a reason for more research, not as proof that vitamin D supplements prevent pain after surgery. Patients preparing for surgery should talk with their medical team before starting supplements, especially during cancer care.
The authors reported that they did not receive a specific grant for this research from any public, commercial or not-for-profit funding agency.