Despite the global focus on understanding COVID-19 and making progress with vaccine candidates, 2021 has been also a fruitful year in gut microbiome research.
Last year a group of scientists under the auspices of the International Scientific Association for Probiotics and Prebiotics updated the definition and potential health applications of postbiotics, defined as “a preparation of inanimate microorganisms and/or their components that confers a health benefit on the host”.
In the light of advances made around the role of microorganisms in protecting human health, scientists have suggested the provocative idea of adapting the concept of RDA (recommended dietary allowance) for microbes, similarly to other nutrients in diet. However, the available body of scientific evidence does not support the use of fermented foods for maintaining health and improving gastrointestinal conditions.
Some advances have been made regarding the potential role of newly identified probiotics in metabolic features of obesity (i.e., the potential candidate Dysosmobacter welbionis for obesity-related metabolic diseases) and functional gastrointestinal disorders (i.e., spore-forming probiotics for functional dyspepsia). It is also important to acknowledge that recent proof-of-principle evidence suggests that, in particular circumstances, focusing on more than one strategy for targeting the gut microbiome and on other host physiological characteristics beyond the microbiome might be worth considering. That is the case with the potential use of fecal microbiota transplants and low-fermentable fiber for improving obesity features. Likewise, the combined targeting of host inflammation and gut microbiota state could pave the way for personalized treatments for ulcerative colitis remission.
Moving to bedside, despite being closely related terms, it is important to remind patients that fiber and prebiotics are not the same. Fiber includes the carbohydrates that are fermentable by the individual’s gut microbiota plus those that remain unfermented and play a bulking role, whereas prebiotics are substrates selectively utilized by host microorganisms that confer a health benefit. While it is likely that many fibers are also selectively utilized by gut microbes, that is not a requirement for fiber. On the other hand, the more recent term “microbiota-accessible carbohydrates” (or MACs) refers to carbohydrates—either from diet, secreted in the intestine by the host, or produced by microbes—that can be metabolically used by gut microbes.
Another topic of interest for healthcare professionals working with patients with functional gastrointestinal disorders is how to make safe use of the low FODMAP diet. Although this exclusion diet has been shown in randomized clinical trials to be effective with regards to the symptoms of IBS, it is not without its challenges, which should be overcome with the support of a registered dietitian. Examples include an altered gut microbiota composition, especially during the initial step of FODMAP elimination, and compromised nutrient intake and diet quality.