The Effects of Gum Chewing in the Postoperative‐Period: A Systematic Review and Meta‐Analysis

ABSTRACT

Objective

Postoperative ileus (POI) is a transient impairment of gastrointestinal motility occurring after surgery. Patients with POI can suffer from complications such as increased risk of nosocomial infections, overall mortality risk, and higher overall healthcare costs. This study aims to (a) evaluate the effectiveness of gum chewing on relieving POI symptoms (b) conduct meta‐analysis on POI outcome variables to estimate overall effect size.

Methods

We searched MEDLINE (Ovid), EMBASE, CINAHL, Web of Science, and Scopus for English language randomized controlled trials (RCTs), evaluating the postoperative effects of gum chewing in adult surgical patients. Two reviewers independently screened titles, abstracts, and full texts, resolving conflicts by discussion. Study quality was assessed using the GRADE system. Meta‐analysis was conducted within two surgical specialty subgroups separately.

Results

From 1925 citations, 714 duplicates were removed. After title/abstract screening, 128 proceeded to full text review, out of which 43 studies met the inclusion criteria. Among RCTs, 69.8% noted statistically significant improvement in at least one of the POI outcomes in the intervention cohort. Meta‐analysis showed significant reductions in time to first flatus (−7.4 h; p = 0.0003) and defecation (−18.64 h; p < 0.0001) in general and colorectal surgery. Similar reductions were also observed in the OBGYN and gynecology cohort: flatus (−6.52 h; p < 0.0001) and defecation (−9.71 h; p = 0.003).

Conclusion

Chewing gum is a safe low‐cost intervention that has the potential to significantly reduce POI symptoms and hospitalization times. Meta‐analysis validated the clinical relevance of the intervention. Standardized protocols are still required to delineate true effect sizes and reduce heterogeneity.

Meta‐analysis supports the use of chewing gum as a successful intervention to relieve postoperative ileus.

1. Introduction

Postoperative ileus (POI) is known to occur following abdominal and non‐abdominal surgeries [1, 2, 3, 4]. The earliest formalized distinction of POI versus ileus came from Livingston and Passaro in 1990, stating that the former is “uncomplicated ileus occurring following surgery, resolving spontaneously in 2–3 days [5]” POI is characterized by transient impairment of bowel function, lack of bowel sounds, pain, accumulation of gas and fluid, nausea, vomiting, abdominal distension, and delayed passage of flatus or bowel movement [6]. Generally, POI lasts for 3–4 days post procedure but could extend beyond the primary ileus and present for more than 7 days [ibid.]. Varying based on the type of surgery, the prevalence of POI in patients ranges from 7% to 27% and accounts for a 66.3% increase in hospital costs per person due to additional stays or complications [7]. In addition, POI is also associated with delayed wound healing, risk of anastomotic failure, pneumonia, venous thromboembolic events, and sepsis while also significantly contributing to overall mortality risk [1, 8, 9, 10, 11]. The pathogenesis of POI is considered multifactorial, attributed to three main underlying mechanisms: overactivation of sympathetic pathways, inflammatory response from the surgical trauma, and from the opioids used in postoperative analgesia [12]. POI has been frequently discussed as a common complication of surgical trauma due to its significant impact on patient recovery and health care resources. This problem has equally frustrated both the physicians and patients while also being estimated to cost the US healthcare system $1.46 billion annually [13]. Various measures such as enhanced recovery after surgery protocols (ERAS) are being incorporated to assist patient comfort and reduce POI duration. ERAS protocols involve a multidisciplinary multimodal approach at peri‐, intra‐, and post‐operative stages based on best available evidence [14, 15]. For instance, one of the regimens included continuous epidural analgesia, early oral nutrition, mobilization, and laxative treatment [16]. Individual contribution of each of the interventions is unclear, and there seems to be a lack of standardization of these regimens [17]. Sham feeding achieved with gum chewing on its own or as a component of ERAS is of particular interest, offering a low‐cost intervention that carries the potential to translate into a high‐impact solution. Gum chewing can induce cephalic‐vagal stimulation, gut motility, and reduction in sympathetic signaling, while also increasing salivary and pancreatic secretions [18, 19]. Our objective of conducting this systematic review is to: (1) consolidate the existing evidence from randomized controlled studies regarding gum chewing and POI (2) utilize the consolidated evidence to conduct meta‐analysis on POI outcome variables to estimate overall effect size.

2. Materials and Methods

Our study protocol was devised in accordance with the International Prospective Register of Systematic Reviews (PROSPERO) registration standards and reported using the Preferred Reporting Items for Systematic Reviews and Meta‐Analyses (PRISMA).

2.1. Search Methods and Information Sources

We developed our search strategy by first reviewing the search strategies of prior publications of gum chewing effects in various patient populations. The following five electronic databases were searched: MEDLINE (Ovid), EMBASE, CINAHL, Web of Science, and Scopus up until November 27, 2024.

2.2. Screening Process

Using Covidence (Veritas Health Innovations, Melbourne, Australia), two independent reviewers (CL, XMZ) screened titles and abstracts of studies retrieved from our search strategy in order to identify studies that met the specified inclusion criteria (Table 1). The full texts of these studies were then independently assessed for eligibility by two team members (CL, XMZ). In cases of disagreement between reviewers, a consensus was reached via discussion.

TABLE 1.

Eligibility criteria of studies.

Inclusion criteria	Exclusion criteria
Data on postoperative gum chewing in adults	Not primary research (commentary, letters, conference abstracts, etc.) Any other sham feeding other than gum chewing Pre‐operative intervention Not in English Full text not available

2.3. Eligibility Criteria

Eligibility criteria are included in Table 1. Our study focused on randomized controlled trials (RCT) evaluating the postoperative effects of gum chewing in adult surgical patients. No publication date or location restrictions were applied. Only articles available in the English language were included.

2.4. Data Extraction

Data were extracted from studies into a predefined form. Three review authors (CL, XMZ, and AN) extracted data from studies including author(s), title, year of publication, country of origin, number of participants (total, control and intervention groups), surgical population, type of surgery performed, gum chewing protocol (occurrence and duration), gum type, and outcome(s) measured.

Quality of evidence was evaluated using the GRADE quality scale and was assessed by 3 reviewers for each of the studies.

2.5. Meta Analysis

Studies were grouped based on specialties: general and colorectal surgeries (n = 23), OBGYN and gynecology (n = 14), and all other specialties (n = 6). Most studied variables, (1) Time to first bowel sounds (TBS), (2) Time to first flatus (TFF), (3) Time to first defecation (TFD), (4) Length of hospital stay (LOS) and (5) Time to first bowel movement (TBM) were explored in each of the subcohorts. Only variables explored and recorded in at least 10 studies were considered for meta‐analysis. To attain a uniform dataset, all observations were converted to number of days from minutes or hours, and in cases where median and ranges were recorded, means and standard deviations were estimated based on methods suggested in Wan et al. [20]. Post standardization, a random‐effects model was used to estimate an overall effect size while incorporating within and between variances across studies. A significance level of 0.05 was used for all analyses. The mean differences were converted to hours for reporting meaningful inferences. All statistical analyses were conducted using R studios (version 4.4.2, R Foundation for Statistical Computing, Vienna, Austria).

3. Results

3.1. Search Results

A total of 1925 studies were identified, with 714 duplicates removed, using the search strategy. These titles and abstracts underwent screening, resulting in 128 studies progressing to full‐text review. Based on our outlined inclusion and exclusion criteria, 43 articles were included in our systematic review (Figure 1). Tables S3–S5 summarize the characteristics of each included study.

FIGURE 1.

PRISMA flow diagram outlining literature search and results of the screening process.

3.2. Study Characteristics

Many of the articles investigating sham feeding originated from Türkiye (n = 8, 18.6%), followed by China (n = 6, 14.63%), and the United States of America and India each publishing (n = 4, 9.3%). Australia, South Korea, and the United Kingdom contributed (n = 3, 6.98%) each, followed by Iran with 2 publications and 10 other countries around the world accounting for one article each. Patients undergoing general and colorectal surgery associated procedures were the most studied cohort, accounting for 53.49% (n = 23) of all the studies in this systematic review. Immediately followed by gynecology and OBGYN cohort amounting to 32.56% (n = 14); while other surgical specialities contributed to the remaining 13.95% (n = 6). While a large fraction of the RCT's (n = 32, 74.42%) were published more than 5 years ago, with only a single study being reported in the year 2024, we can only speculate that the loss of interest could plausibly be due to lack of standardization and concrete recommendations.

3.3. Interventional Preference and Design Variability

It was interesting to note that although there was no standardized brand or type of chewing gum preferred in the studies, chewing gums marketed as “sugar‐free” were reported to be used in 74.42% (n = 32) of the publications. Among these studies we found high variability in frequency, duration, and introduction of gum chewing post‐surgery. We also noted a significant variability in the end point definition of POI. For instance, one study administered chewing gum 6 h post procedure for 30 min q6h until postoperative day 4 [21]; whereas another study introduced the chewing gum intervention 4 h post procedure for 15 min q2h until flatus [22]. Furthermore, even the outcome/indicators used to measure the effectiveness of the sham feeding intervention were not consistent between the studies, ranging from time to discharge, time of feeling hungry, first fluid intake, and appearance of bowel sounds. In spite of the variations in experimental designs, patient populations, sample sizes, and the surgical procedures, we noticed that among all the RCTs an overwhelming majority 69.77% (n = 30) noted statistically significant improvement in at least one of the measured outcomes in the intervention group.

3.4. Common Variables Tested and Consensus

Among the 43 studies included in this systematic review, the most commonly evaluated outcomes included TFF, TFD, TBM, TBS, and LOS. In spite of being commonly evaluated, not all of these outcomes were consistently tested together in each of the studies. In addition, the definition of TBM was noted to be slightly altered in the studies, with some studies defining it as the time to observe the first bowel sounds, whereas the others chose it to be the time of first defecation. Even with this high variability, underlying patterns can be noticed. Out of 39 studies that studied the impact of post‐operative sham feeding on TFF, 53.85% (n = 21) noted a significantly earlier TFF time in the chewing gum cohort, as illustrated in the radial nested plots in Figure 2. Similarly, earlier TFD and TBS times in the intervention group were noted in 65.38% (n = 17/26) and 66.67% (n = 8/12) studies, respectively. The other two variables yielded mixed outcomes: 35.48% (n = 11/31) reported a significant reduction in hospital stay duration, and 27.78% (n = 5/18) observed a significantly earlier first bowel movement in the chewing gum intervention group.

FIGURE 2.

Nested radial plots illustrating the proportion of studies that demonstrated a significant difference between the chewing gum cohort and the control group, focusing on the most commonly tested variables included in this systematic review. (A) Time to first flatus (TFF) (B) Time to first defecation (TFD) (C) Time to first bowel sounds (TBS) (D) Length of hospital stay (LOS) and (E) Time to first bowel movement (TBM).

3.5. Meta‐Analysis

Meta‐analysis was conducted using a random effects model to assess differences in control and chewing gum cohorts in both subsets of surgical specialties. Across 21 colorectal and general surgery‐based studies (pooled sample size; control = 2041, chewing gum cohort = 2022; Figure 3a) the meta‐analysis revealed a significant average reduction in TFF with a pooled mean difference of −7.4 h (95% CI, −11.08 to −3.85 h, p = 0.0003, I ² = 85%). Similarly, pooled across 14 studies (pooled sample size; control = 1782, chewing gum cohort = 1794; Figure 3c) the chewing gum intervention group achieved a significantly lower TFD time with a pooled mean difference of −18.64 h (95% CI, −25.0 to 12.27 h, p < 0.0001, I ² = 96%). On the other hand, LOS achieved borderline overall significance showing a reduction in hospital stay times by −10.61 h (95% CI, −20.97 to −0.25 h, p = 0.0453) with moderate heterogeneity (I ² = 52.4%) in a pooled sample size (control = 1862, chewing gum cohort = 1846; Figure 3b) from 17 studies. Analysis of the OBGYN and gynecology cohort yielded similar results. Among 12 studies, meta‐analysis showed a significant reduction in TFF (pooled sample size; control = 997, chewing gum cohort = 1001; Figure 4a) and TFD (pooled sample size; control = 1000, chewing gum cohort = 1007; Figure 4b) with a mean difference of −6.52 h (95% CI, −8.889 to −4.16 h, p < 0.0001, I ² = 97.3%) and −9.71 h (95% CI, −15.4 to −4.010 h, p = 0.003, I ² = 98.5%) respectively. LOS was opted out of the meta‐analysis due to an insufficient number of studies evaluating it in the OBGYN and gynecology cohort. Summary of mean differences in individual studies is recorded in supplementary Tables S1 and S2.

FIGURE 3.

Forest plots depicting effect sizes on meta‐analysis of colorectal and general surgery studies with chewing gum as an intervention. The vertical line at zero indicates no difference between the groups. Overall pooled mean difference is indicated with the blue diamond and associated 95% confidence interval (a) Time to first flatus (TFF) (b) Length of hospital stay (LOS) c) Time to first defecation (TFD).

FIGURE 4.

Forest plots depicting effect sizes on meta‐analysis of gynecology and OBGYN surgery studies with chewing gum as an intervention. The vertical line at zero indicates no difference between the groups. Overall pooled mean difference is indicated with the blue diamond and associated 95% confidence interval (a) Time to first flatus (TFF) (b) Time to first defecation (TFD).

4. Discussion

In this systematic review, we explored 43 randomized controlled trials that tested the use of chewing gum as an intervention in alleviating POI‐associated symptoms. POI has been a significant issue leading to postsurgical complications and added healthcare costs. In spite of the widespread prevalence of POI (7%–27% depending on surgery type) attempts at reducing the incidence using enhanced recovery protocols remain poorly standardized. Firstly, drawing a cumulative inference becomes challenging due to the lack of consensus regarding a standard definition of POI and variables evaluated as indicators for resolution of the ileus. Even though TFF, TBS, TFD, LOS, and TBM are commonly used outcome indicators, not all of these variables were tested in conjunction in all studies. Notwithstanding these issues, ~70% of the RCTs evaluated in this review report a significant reduction in at least one POI‐associated parameter from the chewing gum group, indicating overall evidence in favor of this low‐cost intervention. More than 50% of the studies testing these variables reported an earlier occurrence of bowel sounds, first flatus, and first defecation in the intervention group compared to the control group, validating the role of sham feeding in improving gastric motility. Additionally, 35% of the studies recorded a reduction in the duration of hospital stays among the sham feeding group, indicating a positive trend, though not definitively conclusive. Secondly, previous research shows an association of POI to factors such as age, male sex, prior instance of abdominal surgery, obesity, and pre‐existing respiratory disorders [23]. Majority of the studies show age, sex, and BMI means to be comparable between control and intervention groups; this is inadequate considering the wide confidence intervals noted in the outcome measurements. Especially with smaller sample sizes, imbalances in baseline characteristics reduce statistical power, and this unaccounted variability would result in reduced precision and increased error. Additionally, the intervention might have had a stronger effect in a certain age group or BMI category, the effects of which would be diluted upon generalization. The appropriate solution would be to incorporate baseline risk factors as covariates while modeling outcomes as a function of the intervention.

Meta‐analysis adds further nuance into the overall utility of chewing gum intervention in a postoperative setting. In general and colorectal surgery cohorts, TFF (−7.4 h), TFD (−18.64 h), and LOS (−10.61 h) the direction of the effect consistently favored reduced times in the intervention group. While TFF and TFD yielded statistically significant pooled effects, LOS showed a borderline significant trend in the same direction. In addition, substantial heterogeneity was noted in TFF (I ² = 85.5%), TFD (I ² = 96%) and while moderate heterogeneity in LOS (I ² = 52.4%) suggesting wide variations in study contexts, as demonstrated by differences in POI end points, the frequency, duration, start time of the intervention, and type of chewing gum used; all contributing to a large degree of heterogeneity among the studies. OBGYN and gynecology cohort yielded similar results with a significant reduction in TFF and TFD of −6.52 h and −9.71 h respectively. Yet again high levels of heterogeneity were denoted by substantially high I ² = 97.3% and 98.5% associated with TFF and TFD respectively. Apart from variable endpoints, considerable variation in sample sizes ranging from 28 [24] to 2000 [25] and even large ranges of measured outcomes leading to wide confidence intervals as depicted in TFF, TFD, and LOS in the meta‐analysis (Figures 3 and 4) further contribute to the high heterogeneity.

Overall, not controlling for the confounding variables and lack of standardization of the experimental designs directly impacts the effect sizes of measured variables and may be one of the reasons why the observations, although statistically significant, achieve moderate clinical relevance. In spite of these limitations, it is worth noting that even an average reduction in POI associated times of ~7–18 h per patient is a meaningful clinical change, especially in high‐demand and resource‐limited settings with a single postoperative intervention.

5. Conclusions

To ensure the applicability of chewing gum as an intervention for POI, several key recommendations should be considered. First, a need for a standardized definition of POI across the studies, with consensus on the outcome variables used to evaluate its resolution, is essential for enabling comparisons across studies. Second, accounting for baseline risk and adjusting for confounding variables should be incorporated to ensure that observed effects truly reflect the effects attributed to the chewing gum intervention. Lastly, the standardization of the frequency, duration, initiation time, and type of chewing gum used is currently a considerable limitation in inferring from all the existing studies. Given chewing gum's low cost and significant potential for improving POI symptoms despite heterogeneity and fragmented data, even with all the limitations of the significant reduction time required for POI‐associated symptoms, we recommend the incorporation of chewing gum 6 h after post‐operation till POI resolution at a frequency of 3 times a day for at least 30 mins—a consolidated protocol from all the studies in this systematic review. A well‐powered study with a standardized experimental design will further improve the effect sizes and be useful for solidifying the role of chewing gum in postoperative care.

Conflicts of Interest

The authors declare no conflicts of interest.

Supporting information

Table S1. (a) TFD (b) LOS (c) TFF in general and colorectal surgery cohort.

Table S2. (a) TFF (b) TFD in OBGYN and gynecology cohort.

Table S3. General and Colorectal surgery studies.

Table S4. Gynecology and OBGYN studies.

Table S5. Other studies.

Li C., Nair A., Zhu X. M., et al., “The Effects of Gum Chewing in the Postoperative‐Period: A Systematic Review and Meta‐Analysis,” ANZ Journal of Surgery 95, no. 7‐8 (2025): 1320–1328, 10.1111/ans.70238.

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.