Studies show role of human gut microbiome in nutrient absorption
Researchers from the NIDDK Intramural Research Program, in partnership with scientists from academic institutions in the United States and Germany, have found that changes in people’s gut microbiomes, due to diet or use of antibiotics, directly altered nutrient uptake, confirming results from animal models and indirect associations. in previous human studies. Decades of research, primarily in animal models, have illustrated how influential gut microbes can be in supplementing individuals’ metabolic machinery and determining how much nutrition is extracted from food. Human studies in this area have produced similar but indirect associations. For example, one study showed that undernourishment (ingesting fewer calories than needed to maintain current weight) reshaped the microbiome and reduced nutrient absorption, but it was not clear whether the effects on absorption of nutrients were directly caused by changes in the microbiome.
The scientists wanted to test whether there was a causal relationship between human gut microbes and nutrient uptake in a controlled feeding study in which participants’ microbiomes were altered by diet or antibiotics. This study design provided an accurate assessment of dietary intake, with adult men and women, some of whom were obese or glucose intolerant, staying at the NIH Clinical Research Unit at Phoenix Indian Medical Center in Arizona. during the entire 31-day study period. During this time, they were given prepared meals, which were closely monitored to ensure that 95% of the food was consumed, and samples were taken. For the first phase of the study, all participants were overfed and undernourished with the same foods for 3 days each, in random order, with a weight-maintenance diet in between. In the second phase, they were fed a weight maintenance diet and given either the oral antibiotic vancomycin or a placebo pill. Scientists measured nutrient absorption by monitoring the calories transmitted in stool and urine samples. They also tracked the activity and composition of the gut microbiome by measuring plasma biomarkers of host and microbial metabolism as well as the number and types of gut bacteria present in the stool. Undernourishment and antibiotics reduced nutrient absorption (i.e. more nutrients were lost in the stool). In the case of undernourishment, scientists have attributed this to reduced availability of nutrients for intestinal microbial metabolism. These short-term dietary changes slightly altered the composition of the gut microbes, and the antibiotic treatment changed it more dramatically, with a loss of gut microbial species diversity, which may have hampered the metabolic capacity of the remaining gut microbes. . In fact, a marker of microbial metabolism was lower in people who were malnourished or treated with the antibiotic, indicating a reduction in nutrient metabolism by the microbiome under these conditions.
This study offers high-quality evidence for a direct role of gut microbes in the amount of nutrients a given person can extract from their food, including the impact of environmental factors such as diet and drug use. ‘antibiotics. These results also support the validity of animal models in which similar results were found. Further and larger human studies are needed to determine the potential therapeutic implications of this research.