Study Suggests Dietary Fibers from Common Trees Promote Gut Health

Jan. 23, 2019
Wednesday, Jan. 23, 2019

Washington, D.C. – January 23, 2019 – Prebiotics are high-fiber compounds that nourish helpful bacterial species in the gut. They’re typically associated with healthy foods like fruits or whole grains, but new research suggests that’s too narrow a way to think about them. A study published in this week’s mSphere suggests that the hemicellulose fibers extracted from ordinary trees can help bring balance to the microbiome.
Findings from lab tests showed that fibers extracted from Norwegian birch and spruce trees promoted the growth of BifidobacteriumLactobacillus, and Bacteroides bacterial species, which among other things promote gut health by protecting against inflammation and colonization by pathogens. The findings suggest that the wood left from construction projects may serve a second purpose inside the intestines, says lead author Sabina Leanti La Rosa, Ph.D., a microbiologist at the Norwegian University of Life Sciences in Aas, Norway.
“We decided to use waste material from construction,” she says. “But that wood is not real waste, it’s a resource of compounds with health-promoting properties,” she says.
La Rosa worked with researchers at her home institution in Norway, as well as at the University of Reading, in the United Kingdom, and at the University of Michigan, in the United States. She says her team began the project with the goal of identifying a plentiful source of prebiotics that was cheap to produce and environmentally friendly.
They knew that some of the most common hemicellulose compounds found in wood have structural similarities to prebiotics found in cereals and beans, which suggests that the wood may similarly confer microbiome benefits.  That similarity led them to look for a source of root biomass close to home, and La Rosa said they quickly realized that Aas is surrounded by thick forests that include spruce and birch, both of which are used in construction.
They tested hemicellulose compounds that had been extracted from the wood using steam explosion, a process that uses high-pressure steam to break down the structure of a tree into a fibrous solid. The researchers conducted culture experiments on those compounds with 43 different bacterial species, all commensal, and compared the results to control experiments using commercially-available compounds sold as prebiotics. In the majority of the experiments, the bacteria grew more in the presence of the wood-derived hemicellulose compounds than in the commercial compounds. In some cases, the experimental compounds led to the growth of bacterial species that didn’t metabolize commercial compounds at all.  
These promising lab tests suggest that the woody compounds have at least as much prebiotic potential as the edible compounds, and the same materials used to build shelters for external protection may confer internal benefits as well. “Everybody in our profession knows that fibers are agents for health and well-being,” La Rosa says, “but it’s amazing that you can have these prebiotics from wood.”
Despite the promising findings, it’s too early to design nutritional interventions based on tree-munching. La Rosa cautions that more testing is needed – next on animals – to better understand how well these findings translate to a real-world, real-intestine setting. 
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