World's first microbiome study reveals links between lifestyle and gut flora

2012 marked the launch of the Flemish Gut Flora Project, initiated by prof. Jeroen Raes (VIB/VUB/KU Leuven). Together with his team, prof. Raes aimed at the ambitious task of mapping the gut flora composition of around 5,000 volunteers in Flanders (Belgium). The purpose of this endeavor was to investigate links between the human gut flora and health, diet, and lifestyle.

Gut flora composition linked to health, diet, and lifestyle

Titled "Population-level analysis of gut microbiome variation," prof. Raes' study has identified 69 factors associated with gut flora composition and diversity. Most of these covariates are related to transit time, health, diet, medication, gender, and age. Integration of the Flemish Gut Flora Project results with other data sets gathered around the world revealed a set of 14 bacterial genera that make up a universal core microbiota present in all individuals.

Jeroen Raes (VIB/VUB/KU Leuven): "Our research has given us a tremendous amount of new insight into the microbiota composition of normal people like you and me. This makes the Flemish Gut Flora Project unique, since the majority of previous studies focused on specific diseases or featured a significantly smaller geographical scope. However, analyzing the 'average' gut flora is essential for developing gut bacteria-based diagnostics and drugs. You need to understand what's normal before you can understand and treat disease."

Beer and buttermilk

Stool transit time showed the strongest association to gut flora composition. Also diet was an important factor, with most associations related to fiber consumption. One of the many surprising findings was the association of a particular bacterial group with a preference for dark chocolate! "The Belgian chocolate effect.," Raes laughs. "As many readers might expect, we also found an association between gut flora composition and beer consumption." Other project results incite deeper investigation, such as the relationship between the gut flora and factors linked to oxygen uptake capacity. Medication also had a strong link to the gut flora profile. The Raes Lab researchers not only identified associations with antibiotics and laxatives, but also with hay fever drugs and hormones used for anticonception or alleviation of menopause symptoms. Remarkably, early life events such as birth mode or whether or not volunteers were breast-fed as babies were not reflected in adult microbiota composition.

Jeroen Raes (VIB/VUB/KU Leuven): "These results are essential for disease studies. 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."

A key factor in this study was the collaboration with the Dutch LifeLines study, which allowed the researchers to replicate their findings: more than 90% of the identified factors were also detected in the Dutch cohort. International collaborations like these are the key for advancing the field and speed up the path to developing gut flora-based drugs. "Such replication adds a tremendous amount of robustness to the results," Raes emphasizes. "Of course, we also found some differences between both cohorts. Believe it or not, but one of the important dietary covariates identified in the Dutch cohort was the consumption of buttermilk."

Tip of the iceberg

Although the Flemish Gut Flora Project has enormously enriched our knowledge on gut flora composition, it only allowed to explain 7% of gut flora variation. An enormous amount of work still needs to be done in order to sketch out the entire gut flora ecosystem. The Raes Lab estimates that around 40,000 human samples will be required just to capture a complete picture of gut flora biodiversity. In other words: we are only seeing the tip of the iceberg. And although the VIB team revealed a wide range of associations, further research is required to unveil what is cause and what is consequence.

This is why this first publication doesn't mark the end of the Flemish Gut Flora Project. The Raes Lab is already planning follow-up studies, including new large-scale research projects that will explore the evolution of gut flora over time. More volunteers are now being recruited for this long-term study. The more people willing to participate, the faster VIB will be able to unveil new insights into the relationship between the trillions of microbes in the human body and our health. "The thousands of volunteers, pharmacists, and healthcare professionals that participated to the Flemish Gut Flora Project are the heart of this study," Raes says. "Without their enthusiasm, this couldn't have been done."