Gum for bowel recovery

“Chewing gum aids bowel recovery” is the headline on BBC News website. Chewing gum “appears to speed up the return of normal bowel function by stimulating nerves in the digestive system”, the BBC reports.

The story is based on a review of studies that compared recovery from abdominal surgery with and without the use of chewing gum in the early period after surgery. Chewing gum helped speed up a return to bowel health after surgery; however, the reduction in hospital stay was not statistically significant. The researchers say that given the potential health and economic benefits to patients and the health system, the use of chewing gum should be further investigated. There are differences in the studies included, which could mean that using a meta-analysis to combine them was not appropriate. A large, high quality, randomised controlled trial is needed to confirm the results, and this seems a sensible way forward.

Where did the story come from?

Dr Sanjay Purkayastha and colleagues from Imperial College London carried out this research. It is unclear how the study was funded. It was published in the peer-reviewed medical journal: Archives of Surgery .

What kind of scientific study was this?

This was a systematic review and meta-analysis of randomised controlled trials that compared outcomes following abdominal surgery – specifically colonic resection – with or without the use of chewing gum in the early period after surgery. The researchers searched literature databases for studies up until July 2006. They only included studies that reported either return of normal bowel function (enteric function) or length of postoperative stay, or both,  those that clearly documented whether or not chewing gum was used, and the reasons for surgery. “Return to enteric function” was measured in two ways, as the time until first flatulence and the time until the first postoperative bowel movement. Length of time in hospital was defined as length of time (in days) between surgery and discharge.

Meta-analysis, a technique used to combine the results from several studies to arrive at a summary estimate, was used to determine whether chewing gum was associated with improved outcomes (i.e. quicker return to normal bowel function or shorter hospital stay).

What were the results of the study?

The researchers found five randomised controlled studies (investigating 158 patients) that met their inclusion criteria. These were combined together in the meta-analysis. Each study involved chewing gum three times a day after surgery for between five and 45 minutes each time, and this was compared with not chewing gum. The studies were of varying quality and were all different from one another in some aspect of their methods (e.g. in the nature of the control group, in blinding or in participant characteristics).

When combining the results, the researchers found that chewing gum significantly reduced the time to first flatulence and to the first bowel movement. Hospital stay seemed to be slightly reduced too, by just over a day, but this was not statistically significant. These results must be interpreted with caution because of significant heterogeneity in the studies (i.e. the differences between the studies may have made combining their results an inappropriate approach).

When the researchers only analysed the three highest quality studies (containing a total of 115 patients), they confirmed that chewing gum reduced time to flatulence by about a third of a day. In this subgroup, the studies were not too different from one another (i.e. a measure of heterogeneity was not significant). When they excluded the two studies that explicitly included patients who had stomas (a surgical opening for the bowel through the abdominal wall to allow elimination of bodily waste), gum seemed to have an even more positive effect, reducing time to first bowel movement by nearly two days and post-operative hospital stay by 2.5 days.

What interpretations did the researchers draw from these results?

The researchers conclude that their systematic review and meta-analysis suggests that chewing gum after bowel surgery can “limit the discomfort of postoperative ileus [the disruption of normal gastrointestinal activity that can happen following surgery] and reduce the length of postoperative stay”.

What does the NHS Knowledge Service make of this study?

The research used recognised methods and sources to search for studies that compared abdominal surgery with and without the use of chewing gum postoperatively.

• The researchers found that chewing gum after bowel surgery may have sped up a return to normal bowel function. Although they found an effect on length of stay in hospital, they say that this was only statistically significant in subgroup analysis. This result must be interpreted with caution given the small size of this subgroup (two studies with only 53 patients overall). 
• The studies included in the meta-analysis had a variety of methods and may differ in the population they included or in how the treatment was given. It is not always appropriate to combine studies that differ greatly from each another. The majority of analyses in this study showed significant heterogeneity, therefore they must be interpreted with caution. 
• The researchers put forward some theories as to why chewing gum might have a benefit on return to normal bowel function, as well as discussing the literature regarding other interventions that are used to reduce ileus.

This study may have identified a cheaper alternative or an approach that can be used alongside other methods to help return patients to health following bowel surgery. Given the small sample size though, it seems sensible to wait for more research before drawing definitive conclusions. The researchers say that “the potential benefits to individual patients, in health economics terms, are such that a well-designed, large-scale, blinded, randomized, controlled trial with a placebo-arm is warranted to answer the question of whether chewing gum can significantly reduce the length of stay after abdominal surgery or whether it merely represents a placebo effect”.