The findings are all the more valuable as the results represent the microbiota composition of the general population. Previous studies have focused on specific diseases or featured a significantly smaller geographical scope.
“Analysing the ‘average’ gut flora is essential for developing gut bacteria-based diagnostics and drugs,” said Professor Jeroen Raes, research leader of the study.
“You need to understand what’s normal before you can understand and treat disease.”
The Flemish Gut Flora Project
Results from the study, known as The Flemish Gut Flora Project, is the culmination of four years of research in which more than 1,000 human stool samples were analysed in order to map the gut flora of around 5,000 volunteers.
All in all, 69 factors were identified as linked to gut flora composition and the onset of various disorders. Most of these factors were related to transit time, health, diet, medication, gender and age.
Integration of the project’s results with other data sets, such as the Dutch LifeLines-DEEP study, revealed a set of 14 bacterial genera that made up a universal core microbiota present in all individuals.
Findings revealed stool transit time as the strongest indicator of gut flora composition. Microbiota richness and evenness were elevated in a specific group of subjects, who were of a lower weight and demonstrated a longer transit time, looser stool consistency and time since previous relief.
As expected, diet remained an important factor, with most associations related to fibre consumption. A second group comprising of individuals with reduced microbiome diversity revealed their preference for white, low-fibre bread.
The Raes Lab researchers found that early-life events such as the method of giving birth or whether they were breast-fed as babies made no difference to microbiota composition as an adult.
“The results suggest that there is still an opportunity to mould the gut microbiome in later years” said Raes.
“We see for example that at age 50, a lot of the initial effect has worn off and has been replaced by another effect, such as diet. So I think there is indeed an opportunity to mould the microbiota using dietary interventions.”
The gut-brain axis
The findings also provide valuable insights into future disease research and clinical studies for a range of conditions including Parkinson’s disease and autism.
The gut’s influence on mental health and well-being is well-known in the field of gastroneuroenterology, where the bidirectional communication is known as the gut–brain axis.
Here, it has been suggested the use of probiotics and prebiotics to alter gut microbiota and influence the gut-brain axis may open up new ways of influencing neuropsychological conditions.
“Our study provides the blueprint of the natural health variation at population level, and identified the factors associated with that variation,” said Raes. “Parkinson’s disease, for example, is typically associated with a longer intestinal transit time, which in turn impacts microbiota composition.
"So to study the microbiota in Parkinson’s disease, you need to take that into account. These and many other observations can help scientists in their research into future therapies.”
Investigations into the microbial communities that exist in human faecal material as well as the gut and their link to disease and well-being have been well documented.
These associations have led researchers to search for specific microbiome-based biomarkers for a wide range of pathologies.
Although the project has enhanced current knowledge of gut flora composition, the researchers revealed that only 7% of gut flora variation had been investigated.
The Raes Laboratory estimated that around 40,000 human samples would be required to categorise the entire gut flora biodiversity.
Published online ahead of print, www.sciencemag.org
“Population-level analysis of gut microbiome variation.”
Authors: G. Falony et al.
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