Does Caffeine Enhance Bowel Recovery After Colorectal Surgery?

Background Postoperative ileus is a frequently occurring surgical complication. It is defined as temporary inhibition of propulsive bowel activity and is manifested by abdominal distention, nausea and vomiting and diet intolerance. It may lead to a prolonged hospital stay, hospital-acquired infections or complications that may require additional treatments (analgesia, intravenous fluid administration, electrolyte replacement, nasogastric tube decompression etc.) and as a result increase medical costs.

Surgeons are continually trying to find ways to shorten postoperative ileus. The means are diverse and include advancing diet as tolerated, avoiding the use of nasogastric tubes, early ambulation, occasional use of gastrograffin or alvimopan (a selective μ-receptor opioid antagonist) and the use of minimally invasive surgery (laparoscopic colectomy) rather than laparotomy. Asao et al showed that chewing gum after laparoscopic colectomy leads to an earlier return of bowel function and shorten the hospital stay, probably via the cephalic-vagal reflex which increase the production of gastrointestinal hormones associated with bowel motility. However, up until now, there has been no strategy or drug that has been consistently effective in accelerating bowel recovery from abdominal surgery.

Coffee is a popular beverage with known influences on the central nervous system and the cardiovascular system. Although coffee can stimulate intestinal function in healthy volunteers, the mechanism by which coffee stimulates intestinal motility is still unknown. The cholinergic anti-inflammatory pathway (CAIP) has been proposed as a key mechanism by which the brain, through the vagus nerve, modulates the immune system in the spleen. Vagal stimulation by nicotine was shown to reduce intestinal inflammation and improve postoperative ileus. It is known that caffeine stimulates vagal activity. An average cup of caffeinated coffee contains 50-150 milligrams of caffeine, depending on the type, concentration and amount of coffee consumed.

The gastrointestinal system can be stimulated by a substantial caloric intake, acidity, osmolality, or volume load. The caloric content of coffee is negligible (approximately 1 kcal/ 100 mL). It has a pH which varies from 5 to 6 (less acidic than other beverages that have no similar effect on the bowel motility). Brewed and filtered coffee is hypotonic (as is water which serves as the control drink in previous studies). Therefore, it seems that the gastrointestinal effect of coffee is most probably not attributed to its physicochemical properties but to the biochemical activity of one or several of the many active compounds in coffee.

In a study that was conducted in 1990, 29% of healthy volunteers claimed that coffee induced a desire to defecate. The effect of caffeinated coffee on recto-sigmoid motor activity was investigated with a manometry. The activity was accelerated four minutes after the intake of either regular or decaffeinated coffee. However, water had no comparable effect on the recto-sigmoid motility. Caffeine, when in the stomach, can act upon gastric myenteric and submucous nerves to induce gastric emptying. The influx of digestive metabolites into the small intestines may stimulate the gastrocolic reflex and be a possible mechanism behind caffeine causing the need to defecate shortly after consumption. The ultimate result of this reflex mediated by caffeine is an increased anal sphincter contraction power and less neural input required to induce contraction (decreased sensory threshold). Rao et al. performed an ambulatory manometry with inserting a catheter through the rectum up to the mid transverse colon. They investigated the effects of 240 mL regular coffee, 240 mL decaffeinated coffee, 240 mL water and a 1000 kcal meal on colonic activity. Regular coffee, decaffeinated coffee and the calorie-rich meal induced more colonic contractions than water. Moreover, regular coffee induced colonic contractions at greater intensity compared to a caloric-rich meal, 60% stronger than water and 23% stronger than decaffeinated coffee. A randomized controlled trial performed in 2012 at the University of Heidelberg among patients after laparoscopic colectomy, studied the effect of coffee on the duration of postoperative ileus. The study showed that the time to first bowel movement was significantly shorter in the group (40 patients) which received 3 caffeinated coffee cups per day compared to group (40 patients) receiving water only. No significant side effects were observed at the active treatment group. Dulskas.A et al. conducted a randomized controlled study in 2015 to evaluate whether consumption of 100 mL coffee is effective in reducing postoperative ileus. The study showed that coffee consumption after colectomy is safe and that decaffeinated coffee was associated with a shorter time to bowel movement and tolerance of solid food but not time to first flatus; caffeinated coffee did not impact the duration of postoperative ileus. In all the studies carried out so far, none could explain the mechanism by which coffee stimulates intestinal motility and the determinant agent for this action is still up for discussion: either caffeine or another component of the coffee, such as chlorogenic acids or melanoidins.