SMOKING alters the gut microbiome--lowering levels of multiple bacteria, including Bifidobacterium
Over one billion people worldwide smoke daily
Study:
Cross-talks between gut microbiota and tobacco smoking: a two-sample Mendelian randomization study
The univariable MR analyses confirmed the effects of smoking on Bifidobacterium abundance, supported by existing population studies. Specifically, the abundance of Bifidobacterium was consistently found to be decreased in current smokers compared to non-smokers.
The study addresses the lack of population-level evidence regarding the causal association between gut microbiota composition and smoking. While previous research suggested a link between smoking and alterations in gut microbiota composition, particularly in Bifidobacterium abundance, comprehensive studies with higher evidence levels for causality were lacking.
The researchers utilized summary-level data from genome-wide association studies (GWAS) for both gut microbial taxa and smoking phenotypes. They employed a two-sample bidirectional Mendelian randomization (MR) design and conducted sensitive analyses to validate their results. Additionally, multivariable MR was performed to evaluate the influence of neurotransmitter-associated metabolites on the observed associations.
Additionally, the study proposed several mechanisms through which Bifidobacterium may influence smoking behavior.
These mechanisms include:
Modulation of the vagus nerve signaling: Bifidobacterium longum was found to send signals to the brain via the vagus nerve, leading to the secretion of higher levels of dopamine. Dopamine is related to the brain's reward function and may reduce smoking addiction by offsetting the euphoria of smoking or the pain of quitting.
Promotion of neurotransmitter synthesis: Bifidobacterium was reported to promote serotonin biosynthesis in colonic enterochromaffin cells. Serotonin has been targeted therapeutically for addiction to substances like alcohol and drugs and may also be relevant for smoking addiction.
Interaction with metabolites or components affecting the central nervous system: Short-chain fatty acids and other metabolites or components of Bifidobacterium may influence smoking behavior through their interaction with the central nervous system.
Cigarette smoke decreases organic acids levels and population of bifidobacterium in the caecum of rats
Study highlight we are interested in: “cigarette smoke changes caecal levels of certain organic acids, the population of Bifidobacterium and the pH in caecal contents of rats”
Smoking and microbiome in oral, airway, gut and some systemic diseases | Journal of Translational Medicine
"In animal models, cigarette smoke decreases organic acids levels and population of bifidobacterium in the caecum of rats [124]. Side-stream smoking increased the abundance of Clostridium and decreased the amount of Lactoccoci, Ruminococcus, Enterobacteriaceae and segmented filamentous bacteria (SFB) in the cecal microflora [125]. In human studies, smoking increased the probability of developing Clostridium difficile infection [126]. Current smokers displayed increased Bacteroidetes and decreased Firmicutes and Proteobacteria in gut microbiota composition community compared with never smokers [127]. Another study also revealed healthy smokers harbour higher Bacteroides–Prevotella (34.8%) than nonsmokers (24.1%)”
Next we are going to dive into bacteriophages versus viruses.