Purpose of Review: Probiotics are promising remedial treatments for symptoms of small intestine (SI) diseases and promoters of overall good health. Probiotics play an important role in supporting a healthy SI microbiome (eubiosis), and in preventing establishment of unhealthy microbiota. SI eubiosis promotes optimal nutrient uptake, and optimal nutritional status maintains a healthy SI, reducing the likelihood of SI diseases. It is important to understand the advantages and limitations of probiotic therapies. Recent Findings: Microbial dysbiosis decreases the capacity of the small bowel to utilize and absorb dietary compounds. In some studies, probiotic supplements containing lactic acid bacteria and Bifidobacterium have been demonstrated effective in supporting beneficial microbes in the SI while improving barrier integrity and reducing nutrient malabsorption and SI disease-related pathology. Summary: Strain-specific probiotic therapy may be a natural and effective approach to restoring SI barrier integrity and eubiosis, resulting in improved nutrient absorption and better health, including reducing the incidence of and severity of SI diseases.

Background: We have previously reported that the addition of resistant maltodextrin (RMD), a fermentable functional fiber, to the diet increases fecal weight as well as the amount of fecal bifidobacteria. Here, we report on the targeted analysis of changes in potentially beneficial gut bacteria associated with the intervention. Objective: The primary objective of this study was to determine the effect of adding 0, 15 and 25 g RMD to the diets of healthy free-living adults on potentially beneficial gut bacteria. Methods: We expanded on our previously reported microbiota analysis in a double-blind, placebo-controlled feeding study (NCT02733263) by performing additional qPCR analyses targeting fecal lactic acid bacteria (LAB), Akkermansia muciniphila, Faecalibacterium prausnitzii and Fusicatenibacter saccharivorans in samples from 49 participants. Results: RMD resulted in an approximately two-fold increase in fecal Fusicatenibacter saccharivorans (p = 0.024 for 15 g/day RMD and p = 0.017 for 25 g/day RMD). For Akkermansia muciniphila and Faecalibacterium prausnitzii, we obtained borderline evidence that showed increased amounts in participants that had low baseline levels of these bacteria (p < 0.1 for 25 g/day RMD). We did not detect any effects of RMD on LAB. Conclusions: RMD supplementation in healthy individuals increases Fusicatenibacter saccharivorans. Albeit to a lesser extent, RMD at the higher intake level may also increase Akkermansia muciniphila and Faecalibacterium prausnitzii in individuals with low baseline levels of those two species. Potential benefits associated with these microbiota changes remain to be established in studies with quantifiable health-related endpoints.

Long COVID, also known as Post COVID-19 condition by the World Health Organization or Post-Acute Sequelae of SARS-CoV-2 infection (PASC), is defined as the development of symptoms such as post-exertional malaise, dysgeusia, and partial or full anosmia three months after initial SARS-CoV-2 infection. The multisystem effects of PASC make it difficult to distinguish from its mimickers. Further, a comprehensive evaluation of the gut microbiome, nutrition, and PASC has yet to be studied. The gut-brain axis describes bidirectional immune, neural, endocrine, and humoral modulatory interactions between the gut microbiome and brain function. We explore recent studies that support an association between alterations in gut microbiome diversity and the severity of acute-phase COVID-19, and how these may be affected by diets rich in antioxidants and fiber. The Mediterranean Diet (MeDi) has demonstrated promising neuroprotective effects through its anti-inflammatory processes. Further, diets rich in fiber increase gut diversity and increase the amount of short-chain fatty acids (SCFAs) within the body-both shown to protect from acute COVID-19 complications. Long-term changes to the gut microbiome persist after acute infection and may increase susceptibility to PASC. This study builds on existing knowledge of determinants of PASC and highlights a relationship between nutrition, gut microbiome, acute-phase COVID-19, and, subsequently, PASC susceptibility.