Western diets, high in fat and simple sugar, may promote the growth of bacteria in the small intestine that increases fat digestion and absorption, a study claims. The study, published in the journal Cell Host and Microbe, determined if microbes were required for digestion and absorption of fats. The researchers from the Midwestern University in the US assessed which microbes were involved, and the role of diet-induced microbes on the digestion and uptake of fats. They conducted a series of experiments to demonstrate that mice reared germ-free (GF) are protected from diet-induced obesity and are unable to absorb fat compared to conventionally-raised mice, also known as specific pathogen free (SPF) mice.
When the germ-free animals are given small intestine microbiota from high fat conditions, they are able to absorb fat, said Kristina Martinez-Guryn, an assistant professor at Midwestern University. The findings suggest that these microbes facilitate production and secretion of digestive enzymes into the small bowel, Martinez-Guryn said. Those digestive enzymes break down dietary fat, enabling the rapid absorption of calorie-dense foods, the researchers said. Additional experiments showed that bacteria-derived bioactive products stimulate absorptive cells in the small intestine to package and transport fat for absorption.
Therefore, bacteria in the small intestine orchestrate a series of events that allow the host to efficiently absorb fat. It is expected that these diet-microbe interactions can lead to over-nutrition and obesity over time, researchers said. While most studies have focused on the large intestine, this study highlights the microbiota in the small bowel, the major site of macronutrient digestion and absorption. Understanding host-microbe interactions in this region has significant clinical implications, especially in preventing and treating obesity and diabetes, researchers said.
“I would say the most important takeaway overall is the concept that what we eat – our diet on a daily basis – has a profound impact on the abundance and the type of bacteria we harbour in our gut,” said Martinez-Guryn. “These microbes directly influence our metabolism and our propensity to gain weight on certain diets,” she said. “Our results suggest that we can use pre- or probiotics or even develop post-biotics (bacterial-derived compounds or metabolites) to enhance nutrient uptake for people with malabsorption disorders, such as Crohn’s disease, or alternatively, we could test novel ways to decrease obesity,” she said.