Colorectal cancer is the third most common cancer and the third leading cause of cancer-related mortality, with rectal cancer accounting for approximately one-third of cases (1). Despite significant advances in neoadjuvant therapy in recent years, surgery remains the only curative treatment for rectal cancer (2). The postoperative recovery of gastrointestinal function is a key factor influencing the quality of postoperative rehabilitation. If gastrointestinal function recovers quickly, patients can resume oral intake early, replenish nutrients, and enhance their confidence and physical strength. However, delayed gastrointestinal function recovery may lead to nausea, vomiting, abdominal distension, or even bowel obstruction, exacerbating patient suffering, increasing the burden, and potentially prolonging hospital stays.

Previous studies have shown that the use of dexmedetomidine during anesthesia, chewing gum postoperatively, administration of probiotics during the perioperative period, and non-steroidal anti-inflammatory drugs can accelerate the recovery of gastrointestinal function after abdominal surgery (3–9). However, the existing methods and their effects remain limited, with various constraints that cannot fully meet the clinical needs of gastrointestinal surgery. Previous studies have shown that nutrition and metabolism play important roles in colorectal cancer (10, 11). Vitamin B1 and B12, as part of the B-vitamin family, have not been explicitly reported in the literature regarding their role in postoperative gastrointestinal function recovery. Nevertheless, based on long-term empirical observations in our department, vitamin B1 and B12 may have potential benefits in promoting gastrointestinal function recovery.

To further explore the role of vitamin B1 and B12 in gastrointestinal function recovery, we selected rectal cancer as a complex disease model. Rectal cancer surgery involves key surgical factors such as enterostomy and sphincter preservation, which can reflect the practical application value of vitamin B1 and B12 in gastrointestinal function recovery. Through univariate and multivariate analyses of patient data, we comprehensively verified for the first time the effect of vitamin B1 and B12 on postoperative gastrointestinal function recovery. With this study, we aim to provide new therapeutic insights for optimizing postoperative gastrointestinal function recovery, particularly in utilizing simple and low-cost treatments such as vitamin B1 and B12, thereby promoting their clinical application.

Rectal cancer accounts for about one-third of colorectal cancers, making it the eighth most common cancer worldwide and the tenth leading cause of cancer-related deaths (1, 13). Surgery remains the only curative treatment for rectal cancer. Total mesorectal excision has become the gold standard for rectal cancer surgery (14). For patients with low rectal cancer, two surgical approaches are available: one is abdominal rectal cancer resection with sphincter preservation, also known as anterior resection, and the other is abdominoperineal resection, which often requires the establishment of a permanent colostomy (15). However, regardless of the chosen surgical method, the recovery of gastrointestinal function is critical to the overall postoperative recovery of patients, especially in the era advocating for enhanced recovery after surgery.

Postoperative gum chewing has been widely proven to accelerate the recovery of gastrointestinal function in abdominal and orthopedic surgeries (3–5, 16, 17). However, the specific mechanism is not yet fully clear. Previous studies suggest that chewing gum stimulates the head-vagus nerve, promotes the secretion of gastrointestinal hormones, and thus stimulates gastrointestinal motility, as well as promotes the secretion of pancreatic juice and saliva, creating a “sham feeding” effect (18). Furthermore, certain types of gum, particularly sugar-free gum, contain ingredients like sorbitol, which may have a laxative effect (18). However, in previous studies, certain exclusion criteria have been set for postoperative gum chewing, such as excluding individuals with a history of abdominal surgery, children, patients with intraoperative or postoperative complications, and common comorbidities such as diabetes (17). This has limited the widespread applicability of this method.

Dexmedetomidine, an intraoperative anesthetic sedative, has been shown to accelerate the recovery of gastrointestinal function (8, 9). However, meta-analyses point out that the evidence is weak and there is a lack of clear dosage recommendations (9). Nonsteroidal anti-inflammatory drugs (NSAIDs) have also been shown to promote gastrointestinal recovery, but existing evidence is insufficient to determine whether selective or non-selective drugs are preferable (7). Additionally, NSAIDs may increase gastric mucosal injury (19). For complex surgeries like rectal cancer, this undoubtedly increases the risk of stress-related gastric ulcers. Some studies have shown that Bacillus subtilis TBC169 probiotics can accelerate postoperative gastrointestinal recovery in gynecological laparoscopic surgery patients (6). However, there are multiple limitations in these studies, such as excluding patients with a history of intestinal surgery and those with long operative times.

Given the limitations of current methods and their limited effectiveness, existing treatments do not fully meet the needs of gastrointestinal surgery clinical practice. Therefore, more simple, cost-effective, and widely applicable options need to be explored. In long-term clinical practice, we observed that vitamins B1 and B12 may have potential benefits in promoting gastrointestinal recovery. Based on this, we conducted a retrospective cohort analysis focusing on the complex condition of rectal cancer surgery.

We first performed univariate analysis on the four groups. The results showed that the p-value from the Kruskal-Wallis test was 0.0152, suggesting significant differences in the first postoperative flatus time among the four groups. However, paired comparisons from the Dunn test indicated that only the group receiving both vitamin B1 and B12 showed a significant difference compared to the no-vitamin group (p = 0.001). This may indicate that vitamin B1 and B12 have a synergistic effect, which is not significant when used alone.

After excluding patients who received only vitamin B1 or only vitamin B12, and considering that gastrointestinal recovery may be influenced by patients’ physical conditions and perioperative procedures, we performed univariate and multivariate linear regression analysis on the first postoperative flatus time. Linear regression was chosen because all patients experienced the event before discharge, the outcome was measured in days, and the data had moderate dispersion, allowing for straightforward interpretation of covariate effects on mean flatus time. Univariate linear regression results showed that intraoperative blood loss, enterostomy, ileostomy, and combined use of vitamins B1 and B12 significantly influenced the time to first postoperative flatus. After removing variables with severe multicollinearity, the results of the multivariate linear regression analysis showed that intraoperative blood loss, ileostomy, and combined use of vitamin B1 and B12 still had significant effects on the time to first flatus. Specifically, increased intraoperative blood loss prolonged the time to first flatus, whereas ileostomy and the combined use of vitamin B1 and B12 significantly shortened it.

The impact of intraoperative blood loss on first flatus time has been reported in previous studies. Extensive blood loss can exacerbate the sympathetic and endocrine stress responses, leading to more intestinal injury and inflammation, thus delaying gastrointestinal recovery (20). Although ileostomy and colostomy did not show significant differences in multivariate regression analysis, they still have some plausibility from a practical standpoint. Generally, small bowel peristalsis recovers the fastest after surgery (within 24 h), followed by the stomach (24–48 h), and then the large intestine (48–72 h) (21, 22). Therefore, a stoma, especially an ileostomy, can shorten the distance from the small intestine to the stoma, which may explain why a significant difference was observed for ileostomy in the analysis.

The mechanism by which combined use of vitamins B1 and B12 promotes gastrointestinal recovery is currently unclear. Both vitamins are B vitamins. Studies have shown that B vitamins are associated with gut microbiota (23). Vitamin B12, also known as cobalamin, is synthesized and utilized by bacteria in the human gut microbiome and may be related to changes in gut bacterial abundance and diversity (24–26). Vitamin B12 injection is commonly used to treat B12 deficiency in patients with malabsorption (24). Additionally, supplementing vitamin B12 may benefit gastrointestinal diseases through its interaction with the gut microbiota (24). Vitamin B1, also known as thiamine, cannot be synthesized endogenously in humans, and its supply is entirely dependent on dietary intake (27). Thiamine deficiency can occur in gastrointestinal surgery, malnutrition, refeeding syndrome, and alcoholism (28). Thiamine deficiency inhibits pancreatic acinar cells, significantly reducing digestive enzyme secretion (29). Some studies also suggest that thiamine can alleviate symptoms of abdominal pain, nausea, vomiting, and anorexia (30, 31). In terms of safety, both vitamins B1 and B12 are water-soluble vitamins with short half-lives and are rapidly excreted from the body (32, 33).

Although our study is the first to demonstrate that combined use vitamin B1 and B12 can accelerate postoperative gastrointestinal recovery in patients with rectal cancer, several limitations should be acknowledged. First, the number of patients receiving vitamin B1 or B12 alone was small, and these groups were excluded from the primary analysis, which may introduce potential bias. Therefore, larger studies are needed to clarify the independent effects of vitamin B1 and B12. Second, the precise mechanisms by which the combination of vitamin B1 and B12 promotes gastrointestinal recovery remain unclear and warrant further basic and clinical investigation. Third, as this was a retrospective study, the recording of time to first postoperative flatus was not standardized; for convenience, the values were rounded, which may reduce precision and introduce some error. Finally, although no patients received vitamin B1 or B12 preoperatively, their baseline levels were not routinely measured in prior clinical care, highlighting the need for future prospective studies to assess this factor more comprehensively.

The combined use of vitamins B1 and B12 offers a new, simple, cost-effective, and safe treatment option for promoting gastrointestinal recovery after rectal cancer surgery, but further research is needed to establish its broad clinical applicability and elucidate its mechanism of action.