A group of researchers at Southern Medical University, in Guangzhou, China, have studied the impact of prebiotic supplementation on the metabolism of healthy adults.
Research has shown that differences in gut microbiota composition are associated with the development of insulin resistance and type 2 diabetes.
This is the result of intricate and complicated processes that transform the food we ingest into a myriad of metabolites that enter the circulation and fulfill or adversely affect various functional and metabolic processes in the body.
Prebiotic supplementation is one strategy that could improve gut microbiota composition by selectively stimulating the growth of certain beneficial bacteria.
One of the ways that prebiotics or fermentable dietary fibres can improve the gut microbiota is through raising the number of butyrate-producing bacteria.
People with type 2 diabetes as well as obese people tend to have decreased butyrate-producing bacteria and, in many studies, an increased concentration of butyrate is associated with improvements in metabolic health.
The goal of this study, published in Scientific Reports, was to test the efficacy of supplementation with two different kinds of prebiotic fibres, called fructo-oligosaccharides (FOS) and galactooligosaccharides (GOS).
Researchers looked at whether butyrate-producing bacteria were able to grow on FOS and GOS, and what effects they individually had on glucose metabolism.
A total of 35 healthy adults received 16 g of FOS or GOS in a blind cross-over design for 14 days after which time researchers analysed their glucose tolerance test results, fasting glucose response, body composition and fecal samples.
After the 14-day interventio, they found that neither FOS or GOS had a significant impact on body weight, body mass index (BMI), body fat, visceral fat or the basal metabolic rate (BMR).
Although still within the normal range, fasting blood sugar levels increased slightly after 14 days of GOS supplementation while the FOS intervention led to a somewhat impaired glucose tolerance.
In terms of changes in gut microbiota composition, there was a significant increase in the abundance of bifidobacterium, both with FOS and GOS, which can theoretically support a healthy balance of beneficial and less beneficial gut bacteria.
However, the diversity of the microbial community did not improve and was actually lower in the GOS group. Furthermore, butyrate-producing bacteria were decreased with FOS and GOS, as partly evidenced by a lower fecal concentration of butyric acid.
The results therefore fell short of expectations when it comes to raising butyrate and improving metabolism and show that FOS and GOS have at best a neutral effect on gut microbiota composition.
Overall, further long-term studies are needed to evaluate the efficacy of prebiotics and investigate about their effects on blood sugar control.

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