A “groundbreaking” study suggests that a diverse range of gut bacteria – far more than previously assumed – can bind to inulin, revealing the extensive effects of the prebiotic, say Austrian researchers.
The findings, published in Nature Communications, are hoped to advance our understanding of how prebiotics affect the human gut microbiome.
The scientists, from the Centre for Microbiology and Environmental Systems Science (CeMESS) at the University of Vienna, hope that their method will also prove a pioneering step towards personalised dietary supplements.
Inulin, a prebiotic fibre derived from chicory, has increasingly captured the attention of the food and supplement industry in recent years. It is one of the most popular commercial prebiotics, with increased demand for its use in powders and functional food and drink fuelling sales.
Its rise in popularity is part of a wider consumer trend, as concerns around obesity and digestive conditions, coupled with a greater awareness of the importance of holistic gut health, drive demand for prebiotics – non-digestible food components that promote the growth of beneficial microorganisms in the gut.
In addition to its use in adult products, inulin is increasingly added to infant formula or milk to improve the intestinal microflora of babies and small children; its neutral taste makes it an ideal ingredient for this consumer group.
Studies have shown that inulin, which is found in foods including bananas, wheat, onions, and garlic, may have benefits for human health, including anti-inflammatory and anti-cancer properties. However, the complex nature of the human gut, which is home to about 100 trillion microbes, poses a challenge in deciphering its exact effects.
Meanwhile, research suggests that large quantities of inulin may be harmful for gut health by only feeding certain microbes and thus reducing bacterial diversity.
The researchers used fluorescence-labelled nanoparticles to track the interaction of inulin with gut bacteria.
When incubated with human stool samples, these inulin-grafted nanoparticles yielded a surprising result: a far wider range of gut bacteria than previously known about can bind to inulin.
"Most prebiotic compounds are selectively utilised by only a few types of microbes," said lead researcher David Berry. "But actually, we found that the ability to bind to inulin is really widespread in our gut microbiota."
Using a state-of-the-art technique to identify cells actively synthesising proteins, the team discovered that a diverse group of bacteria actively responds to inulin, including some species not previously associated with this capability, such as members of the Coriobacteriia class.
"Inulin supplements have been on the market for years, but precise scientific evidence of their health-promoting effects has been lacking," said Berry.
"We used to think that inulin mainly stimulates Bifidobacteria, the so-called ‘good bacteria’, but now we know that the effect of inulin is much more complex. Our study is a trailblazer for the future of microbiome-based medicine: with our method, dietary supplements can be personalised, precisely designed, and scientifically substantiated in the future."
Co-study leader Alessandra Riva said: "Interestingly, when comparing stool samples from different individuals, we noticed significant differences in the microbial communities that respond to inulin.
"These findings highlight the importance of considering individual differences in the development of dietary recommendations and microbiome-based interventions."
The research not only contributes to a better understanding of prebiotic metabolism in the human digestive tract but also to a better framework for its investigation, the authors argue.
"Our approach to marking and sorting cells based on their metabolic activity is relatively new," added Riva. "We hope that our study can serve as a framework for future research and the development of new microbiome-based therapies."
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