Letter to the Editor about Effect of chewing gum on clinical outcomes and postoperative recovery in adult patients after gastrointestinal surgery: an umbrella review

Dear Editor, I read with great interest the recently published review1, which examined the effectiveness of chewing gum on postoperative recovery indicators, including time to first flatus, time to first bowel movement, length of hospital stay, and postoperative complications, in adult patients undergoing gastrointestinal surgery. While the topic is clinically relevant and the breadth of the synthesized literature is commendable, several methodological and interpretive issues warrant attention before any firm clinical recommendations can be made. The meta-analysis noted that, according to the AMSTAR-2 criteria, 13 of the 17 included systematic reviews were rated as “critically low” in quality, with only one review meeting high-quality standards. This raises serious concerns about the stability and reliability of the pooled conclusions. Key AMSTAR-2 domains were frequently unmet: more than 75% of the reviews lacked prospective registration, 82% failed to justify study exclusions, and most did not appropriately address risk of bias. In addition, nearly all reviews omitted an assessment of publication bias and did not account for study-level bias when interpreting their findings. Given that the credibility of an umbrella review rests heavily on the methodological rigor of its component reviews, the current evidence base appears fragile. The corrected covered area of 11.10% indicates substantial overlap among the included studies, meaning many effect estimates were repeatedly synthesized across different reviews. Such redundancy risks creating an illusion of consistency while drawing from a limited and heterogeneous trial pool. Moreover, 93% of the meta-analyses showed moderate to high heterogeneity (I2 > 50%), undermining the comparability of the underlying studies. Although the review explored sources of heterogeneity, such as surgical technique, perioperative care differences, or cancer status, through basic subgroup analyses, many analyses remained underpowered. Despite acknowledging that most pooled effect sizes represented “weak evidence,” the review still concluded that chewing gum “may significantly aid postoperative care” and recommended its incorporation into clinical practice. Time to first flatus (TFF) and time to first bowel movement (TFBM) are commonly used markers of gastrointestinal recovery but are subjective and prone to reporting bias2,3. Few primary studies used standardized definitions or blinded assessment, which should temper the strength of the conclusions. Similarly, the reported 0.59–0.98-day reduction in hospital stay must be interpreted in context. Such small absolute differences may fall within institutional practice variation and may not translate into meaningful cost savings or improvements in patient experience. Most of the included trials were conducted before enhanced recovery after surgery protocols became widespread. Modern perioperative care emphasizes early feeding, multimodal analgesia, and mobilization, which likely diminishes the added value of the “sham-feeding” effect produced by chewing gum. Without analyses comparing pre-ERAS and ERAS-integrated settings, the applicability of the findings to contemporary practice is limited. Given the broad appeal of chewing gum as a low-cost, low-risk intervention, high-quality randomized controlled trials remain justified. Future studies should employ standardized definitions of gastrointestinal recovery, register protocols with prespecified outcomes and analysis plans, and assess patient-centered endpoints, such as comfort, satisfaction, and tolerability, rather than relying solely on surrogate markers. Although the review offers a useful synthesis of existing literature, the pervasive low quality of the included studies, pronounced heterogeneity, and methodological shortcomings caution against drawing definitive clinical recommendations. Chewing gum remains a promising adjunct, but its benefits should be confirmed in rigorously designed, contemporary trials. Finally, this paper complies with the TITAN guidelines regarding the disclosure of artificial intelligence4. Ethical approval None.