GUT MICROBIOTA, PREBIOTICS, PROBIOTICS, AND SYNBIOTICS IN ANAGEMENT OF OBESITY AND PREDIABETES: REVIEW OF RANDOMIZED CONTROLLED TRIALS

Objective: To review the data from randomized controlled trials (RCTs) for the roles of microbiota, pre-, pro-and synbiotics in metabolic conditions (obesity, prediabetes, and diabetes mellitus type 2 [DM2]). Methods: Primary literature was reviewed on the topics including RCTs of pre-, pro-and synbiotics use for metabolic disease. Results: Gut bacteria (microbiota) benefit digestion and have multiple other functions. Microbiota could increase harvesting of energy from the food and cause subclinical inflammation seen in metabolic disorders. Diet-related interventions including prebiotics, probiotics, and synbiotics (combining pre-and probiotics) may benefit metabolic conditions. Prebiotics are complex carbohydrates (i.e., dietary fiber). Results of RCTs of prebiotics suggested a neutral effect on body weight, decreased fasting and postprandial glucose, and improved insulin sensitivity and lipid profile. Some inflammation markers were reduced, sometimes substantially (20-30%). RCTs for probiotics demonstrated significant but small effects on body weight (<3%) and metabolic parameters. The effect was seen mostly with fermented milk or yogurt compared to capsule form, consumption for at least 8 weeks, and use of multiple rather than a single bacterial strain. Changes in microbiota were seen at times with both pre-and probiotics. Pickled and fermented foods, particularly vegetables and beans, could serve as a dietary source of pre-, pro-, and synbiotics. These foods showed possible benefits for morbidity and mortality in prospective cohort studies. Conclusion: Pre-, pro-, and synbiotics could prove useful, but further research is needed to clarify their clinical relevance for the prevention and management of metabolic disease.