Cellulose-based thickening agents found in common foods can be digested, study finds

A new study from researchers at the University of British Columbia, in the US, finds that cellulose-based thickening agents found in common foods can be digested, challenging long-held beliefs about how the gut deals with them.

The study, published in the Journal of Bacteriology, offers new insights into how these food additives are actually digested by our gut bacteria because of the natural polysaccharides in diets.

It showed that gut bacteria can feed on these large molecules, something previously thought impossible.

“Researchers assumed that these thickening agents, which are artificial derivatives of natural cellulose, just pass right through the digestive system unaltered,” says Dr. Deepesh Panwar, a postdoctoral fellow at the Michael Smith Laboratories and lead author of the study published in the Journal of Bacteriology. 

“But our study provides a first glimpse at how these food additives are actually digested by our gut bacteria thanks to natural polysaccharides in our diets.”

Cellulose derivatives can be used as thickening agents in products such as ketchup and salad dressing. 

The in vitro study shows that cellulose derivatives can be digested if our gut bacteria are ‘primed’ with natural polysaccharides — long chains of sugars found in fruits, vegetables, and cereals. 

This is because natural polysaccharides activate enzymes produced on bacteria cell surfaces, which can also break down artificial cellulose molecules.

The new research suggests that more work should be done to explore the physical, chemical, and biological effects of gut bacteria’s digestion of cellulose derivatives.

“It was really unexpected for us to see that these cellulose derivatives are in fact used as a source of sugar for bacterial growth,” says Dr. Harry Brumer, a professor in the Michael Smith Laboratories and Department of Chemistry. “It is always a surprise when a new finding goes against the conventional wisdom, in this case showing that these common additives are not just inactive thickeners.