Vitamin D is a secosteroid hormone critical for calcium and phosphate metabolism, bone health, and immunomodulation. In surgical populations, it plays an emerging role in modulating immune responses, reducing postoperative complications, and supporting recovery, particularly when preoperative levels are deficient. Low vitamin D status is highly prevalent in patients undergoing surgery and has been linked to adverse outcomes across a range of surgical specialties.

Mechanisms of Action and Benefits

Immunomodulatory and Anti-Inflammatory Effects
The active form of vitamin D, 1,25-dihydroxyvitamin D, regulates both innate and adaptive immunity by enhancing macrophage function, promoting antimicrobial peptide synthesis, and suppressing pro-inflammatory cytokines such as TNF-α and IL-6 [1,2]. These effects may reduce the risk of postoperative infections and inflammatory complications during the vulnerable perioperative window.

Endothelial Stabilization
Vitamin D helps stabilize endothelial membranes and improve vascular integrity, which may support microcirculatory function during and after surgery [2]. This effect can reduce capillary leak, edema, and systemic inflammation, particularly in procedures associated with high inflammatory burden.

Association with Postoperative Complications
Observational studies show a strong inverse relationship between preoperative vitamin D levels and the risk of postoperative complications, including infections, cardiovascular events, and in-hospital mortality [3]. In a large cohort of noncardiac surgical patients, those with serum 25(OH)D <13 ng/mL had the highest risk, whereas higher levels were linked to a linear decrease in adverse events [3]. In cardiac surgery, low levels of 1,25-dihydroxyvitamin D were independently associated with increased infection rates [4]. Similarly, in colorectal liver metastasis surgery, patients deficient in vitamin D had a higher rate of surgical and infectious complications [5].

Renal Protection and Cognitive Support
Vitamin D status also influences renal outcomes. Low levels have been associated with a greater risk of postoperative kidney injury [9]. Preclinical data suggest that vitamin D may mitigate surgery-induced neuroinflammation and cognitive impairment by modulating NLRP3 inflammasome signaling—a promising avenue for future investigation into its role in preventing postoperative cognitive dysfunction (POCD) [10].

Clinical Implications

Vitamin D deficiency is common among surgical patients and associated with increased risks of infection, cardiovascular complications, and mortality. While randomized trials on perioperative supplementation have produced mixed results regarding mortality or length of stay, there is evidence for benefit in reducing atrial fibrillation, ventilation time, and hospital stay in cardiac surgery, as well as modest improvements in pain control and inflammatory markers in general surgical populations [6,7,8].

Summary

• supports immune regulation, inflammation control, and endothelial stability during surgical stress.
  
• Severe deficiencies (<13 ng/mL or <25 nmol/L) is associated with higher rates of infectious, cardiac, renal, and surgical complications [3–5,9].
  
• well-tolerated and may improve recovery, particularly in high-risk populations or those undergoing major surgery.

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