London, June 24 (IANS): Lifestyle factors that are associated with a Parkinson's disease (PD) risk may be influenced by the bacteria living in the human gut, says a new study.

The gut mediates the effects of various chemicals and nutrients on disease processes. By reviewing the studies related to gut motility to microbiota compositions, the authors suggested there might be complex relationships between coffee, microbiome concentrations, and the altered gut motility found in PD patients.

"Considering the gastrointestinal involvement in PD, it was recently speculated that the associations between smoking, coffee, and PD risk could be mediated by gut microbiota," said lead investigator Filip Scheperjans from the Helsinki University Hospital.

The literature review indicated that smoking affects gut microbiome composition and this seems to be associated with improved barrier function and anti-inflammatory effects in the colonic mucosa.

"Also a possible reverse effect of gut microbiota on smoking propensity and its relevance for PD is an interesting field for future studies," Scheperjans said.

In the case of coffee consumption, most of the direct effects on the GI tract are related to gut motility such as gastro-esophageal reflux, gallbladder contraction, and increasing colonic motor activity.

Intriguing associations have been reported based on which microbiota could indeed play a role at the interface between environmental and lifestyle factors and PD.

The most promising domains seem to be related to gut barrier function, inflammation, oxidative stress, gut motility and metabolism.

"By studying these, we may gain more insight into the hugely complex network of microbiome-host-interactions underlying the observed associations," Scheperjans said.

"Considering the well-established gastrointestinal abnormalities in PD and the vast interactions of gut microbiota with the human host, it seems mandatory to explore whether gut microbiota are involved in this devastating disorder," Scheperjans added.

The study was reported in the Journal of Parkinson's Disease.