PhD defence Colin Andreas Jan van Kalkeren

Keywords: Dietary fibers, Plant-based diets, Microbiome, Metabolism

"Dietary Fibers, Plant-based Diets, and Human Health: From the Gut Microbiome to Metabolism and Cognition"

In this thesis, the effects of dietary fibers (within a protein-rich, partially plant-based diet) on human health, including insulin sensitivity, neurocognition, and food-related brain activity have been evaluated in individuals with overweight/obesity and disturbed glucose homeostasis. 

Dietary fibers are generally fermented by bacteria in the colon, producing substrates that benefit insulin sensitivity, inflammation, and brain processes. 

In general, dietary fibers are fermented rapidly once entering the colon, although the aforementioned effects occur predominantly after fermentation in the distal part of the colon. The investigated fiber mixture, showing distal fermentation in a colonic model, was hypothesized to improve metabolism. 

However, the dietary fibers, combined with the protein-rich diet, induced rather negative metabolic effects, while the group only adhering to the partially plant-based protein-rich diet improved. This suggests that the interaction between dietary fibers, (plant-based) proteins and the gut microbiome is more complex than expected. Even though dietary fibers generally induce benefits for host health, the interactions with other food compounds is in need of further research.

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