For Your Microbiome, How You Eat Could Be As Important As What You Eat

A research group led by Assistant Professor Sayaka Katagiri, of the Periodontology and Associate Professor Haruka Tohara of the Gerodontology and Oral Rehabilitation, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University have demonstrated the importance of oral food intake from a view of microbiology. This study was supported by the Ministry of Education, Culture, Sports, Science and Technology's Grants-in-Aid for Scientific Research and the 8020 Promotion Foundation's 8020 Research Project.

After a stroke, many patients are incapable of oral nutrition and require tube-feeding. Swallowing training is one of the rehabilitation techniques available to help patients reacquire oral nutrition, and numerous previous studies have reported its efficacy for this purpose. The oral cavity and the large intestine are connected by the intestinal tract to which the action of swallowing sends food, saliva, and oral microbes; hence, these factors have the potential to affect changes in the intestinal flora. However, it was unclear just how oral nutrition might influence intestinal flora. The research team in the present study therefore examined the relationship between the reacquisition of oral nutrition and oral and intestinal floras from a bacteriological perspective.

The present study enrolled eight patients who were on tube-feeding during the subacute stage of stroke, then re-initiated oral nutrition after received swallowing training. Saliva and stool samples were collected during the period of tube-feeding before the start of dysphagia rehabilitation and after the re-initiation of oral nutrition following the rehabilitation. The caloric intake of the patients was kept constant during this period. Thereafter, a next generation sequencer was used to identify the oral and intestinal flora species, to analyze the correlation among the bacterial species, and to reveal the predicted functions (functional genes) of the organisms. The results showed that the re-initiation of oral feeding had increased the diversity of oral and gut microbiome.

Moreover, the family of Carnobacteriaceae and genus Granulicatella were increased both in the mouth and gut following the re-initiation of oral food intake. In addition, the network structure showing the correlation among the various bacterial species also changed both in the mouth and gut after re-initiation of oral food intake into such that more bacteria were present in a single network. A comparison of the tube feeding and oral nutrition periods based on the results of the function prediction analysis revealed that the oral nutrition could induce more expression of metabolic pathways.

The research team found that dysphagia rehabilitation in patients with dysphagia not only restored their oral food intake capability but also increased the diversity of oral and gut microbiome, modified the composition of the microbiota, and influenced their co-occurrence network structure. While it was already known that intestinal flora has various effects on many kinds of diseases, the present study demonstrated from a view of microbiology that the re-initiation of oral food intake is also crucial for maintaining health, and may thus be important for designing future treatment strategies.

Reference

Katagiri et al. (2020) Re-initiation of Oral Food Intake Following Enteral Nutrition Alters Oral and Gut Microbiota Communities. Frontiers in Cellular and Infection Microbiology. DOI: https://doi.org/10.3389/fcimb.2019.00434

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