Nutrition and the gastrointestinal tract: Edited by Maria Isabel Toulson Davisson Correia and Miquel A. Gassull
Writing an editorial is always a challenge because it is the author's perception of what they have read, preferably unbiased and, at the same time, with enough information to trigger the reader's curiosity for what is going to come up. However, this year's editorial has been made easy by the variety and quality of the updated and provocative topics. It is a real journey into the world of what we think we already know… virtually nothing! Thus, I invite you to share with us the fascinating manuscripts ahead. Let us start with a bit of flavor, ‘tasting’ what each of them has to offer to the readers.
Who among us has not been questioned by patients or friends on the reasons for that bad breath they have? This is one of the very common questions posed by lay people for which very few health professionals have an adequate reply. Stephen Porter has elegantly explained that the transient altered breath smell usually reflects the effects of foodstuffs, whereas long-standing halitosis is almost always due to oral disease such as gingivitis or periodontitis. Halitosis derived from the mouth reflects the generation of volatile sulphur compounds and short-chain fatty acids by microbial putrification of food debris, cells, saliva and blood. Halitosis derived from gastrointestinal diseases may be associated with unrecognized factors such as gastric, duodenal or esophageal diseases. According to the author, there are robust data indicating a link between upper gastrointestinal tract and halitosis, thus implicating that such diseases should be searched upon and the treatment will of course depend on the primary cause.
Chowdhury and Lobo (pp. 469–476) have offered us with a very complete review of fluid and electrolyte imbalance as risk factors for gut dysfunction. As a surgeon trainee, some years ago (maybe too many years ago …, although not enough to have seen such old paradigm changed), I was made to believe that colon operations were necessarily associated with postoperative ileus. Therefore, right before the beginning of the operation, a nasogastric tube was placed to resolve such a problem. The fact is that these patients remained on nil per os for longer periods and intravenous solutions were used and not necessarily individually estimated. So the question that we now raise is was it a common colonic associated problem or a consequence of overhydration? Chowdhury and Lobo (pp. 469–476) state that a striking balance, in terms of both fluid composition and volume, is likely to reduce the morbidity associated with interstitial edema, a frequently observed occurrence with contemporary perioperative fluid regimens. According to the authors, this balance may be best achieved using individualized and goal-directed approaches to fluid therapy in order to provide fluid when it is needed and in the correct quantities. This particular concept is further discussed by Gustafsson and Ljungqvist (pp. 504–509), who very well define the importance of organized individual protocols in the caring of surgical patients. Numerous surgery-related factors, including adequate pain control, included in the so-called multimodal approaches, definitely impact on patients’ outcome, decreasing morbidity, mortality and length of hospital stay, thus overall costs. Immune nutrition is something to be further discussed in surgical patients as several controlled randomized studies and systematic reviews indicate that immune nutrition formulas reduce both morbidity and length of stay after major abdominal surgery.
New insights into the link between anorexia nervosa, a well known psychiatric disorder, and the gut have been extremely well discussed by Fetissov and Déchelotte (pp. 477–482), who have dedicated the last couple of years investigating such an intricate axis. After reading their article, one will be made to believe that the gut is for sure one of the triggering events related to such a disease. And the question is how can this be possible? Apparently, the millions of bacteria that outsize the number of human body cells play an important role in such aspect. According to the authors, the gut microbiota has been identified as the main source of highest biological variability confined in an individual and also provides constant antigenic stimulation shaping up the physiological immune response. Furthermore, molecular mimicry has been shown between microbial proteins including gut microbiota and several key neuropeptides involved in the regulation of motivated behavior and emotion. Immunoglobulins reactive with these neuropeptides have been identified in humans, whereas their levels or affinities were associated with neuropsychiatric conditions including anxiety, depression, eating and sleep disorders.
Who would have thought that obesity, diabetes and insulin resistance could one day be temptatively treated by targeting the intestine? The gut microbiota is once more the focus of another very elegant article by Esteve et al. (pp. 483–490), who discuss the interactions between the microbiota and obesity, insulin resistance and type 2 diabetes. According to the authors, these disease states are associated with specific changes in the gut microbiota composition. The mechanisms underlying the association between specific gut microbiota and metabolic disease include increasing energy harvest from the diet, changes in host gene expression, energy expenditure and storage and alterations in gut permeability leading to metabolic endotoxemia, inflammation and insulin resistance. In some studies, the modifications of gut microbiota induced by antibiotics, prebiotics and probiotics led to improved inflammatory activity in parallel to amelioration of insulin sensitivity and decreased adiposity.
Finally, but not lastly, Quigley (pp. 497–503) presents us with convincing data on the role of microbiota in the pathogenesis of intestinal bowel syndrome (IBS) and inflammatory bowel disease (IBD). According to the author, several studies implicate that there is a stronger link between the microbiota of those with IBS and IBD when compared with control individuals. In fact, using either antibiotics or probiotics, in selected circumstances, may alter the clinical course of such diseases.
In conclusion, novel approaches to some old important and unsolved clinical states have been discussed, and I have to admit that the session is almost totally dedicated to our friends or enemies: the bacteria! Enjoy reading it!
Conflicts of Interest
There are no conflicts of interest.