The effects of fasting and starvation on the microbiome

Researchers at St. Mary’s University, in Texas, published a study in FEMS Microbiology Ecology about the impact that fasting and starvation have on the gut microbiome. Organisms from five different vertebrate classes were studied and the changes in the composition of their colon and cecum microbiome were observed in response to different fasting periods.

Results differed among the animals studied in terms of diversity of their colon microbiome. Tilapia showed a continuous increase in diversity, southern toads showed a 33% increase in early-fasting and a 51% increase in late-fasting, leopard geckos showed no difference, Japanese quail showed less diversity in long-term fasting, and weanling mice showed a 15-22% increase in diversity. Results for the observed cecum microbiome phylogenetic diversity, compared to the respective nourished vertebrates, are as follows: Tilapia showed a decrease in diversity, quail showed a decrease at the early-fasting stage but a return to normalcy at later stages, mice showed no changes.

The only similarity in colon bacteria identified from this study was that the tetrapods (toads, geckos, quail, mice) all showed a decrease in abundance of Coprobacillus and Ruminococcus. In the cecum, tilapia, quail, and mice showed an increase in Oscillospira and a decrease in Prevotella and Lactobacillus. While it must be considered that these diverse hosts tend to house different microbial communities when healthy, which can account for the few similarities observed between the different vertebrates, the study results are important because they show that microbial responses to prolonged fasting varies between vertebrates.  

While these studies were conducted in non-humans, we know that starvation results in important changes in the microbiome.  People around the world suffer from starvation and malnutrition, and it is not only because they lack food and nutrients.  Instead they suffer from immature microbiomes, which can severely impact health.  Furthermore, diet interventions only temporarily repair the microbiome, so the effects of malnutrition persist after the intervention ceases.  Finally, the differences in microbiomes between developed nations and traditional societies may even play in a role in vaccine effectiveness, as we have previously discussed in our blog.

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