A growing body of evidence suggests that robust postoperative immune function is associated with a lower risk of surgical site infections (SSIs). At the same time, vitamin D is increasingly recognized as a key regulator of the innate and adaptive immune systems. The investigators elected to conduct the current study in patients who will undergo colorectal surgery since these patients are historically at higher risk of developing SSIs and therefore would be ideal for future investigations.

While vitamin D insufficiency \[25(OH)D \<30 ng/mL\] is common in the general population, hypovitaminosis D may affect 40-80% of patients in the perioperative setting. Recent evidence also suggests that surgical stress may be associated with a 40% reduction in circulating 25(OH)D levels when compared to preoperative values. Moreover, the derangement in perioperative 25(OH)D levels may be sustained for up to 3 months after surgery. This finding has potential implications regarding modifiable risk factors for surgical site infections (SSIs), which account for nearly 40% of all nosocomial infections. On aggregate, SSIs result in 3.7 million extra hospital days per annum and an added burden of $1.6 billion in annual healthcare costs. A growing body of evidence suggests that robust postoperative immune function is associated with a lower risk of SSIs. At the same time, vitamin D is increasingly recognized as a key regulator of the innate and adaptive immune systems. Yet, optimization of perioperative vitamin D status remains grossly understudied. Although our overarching aim is to study the impact of vitamin D status on SSIs, the focus of the current investigation is to determine whether the administration of a "bolus" oral dose of cholecalciferol (vitamin D3) in the preoperative setting alters vitamin D status in the perioperative setting (compared to a placebo). The investigators elected to conduct the current study in patients who will undergo colorectal surgery since these patients are historically at higher risk of developing SSIs and therefore would be ideal for future investigations.