Prebiotics: The Concept Revisited Original paper

What was reviewed?

This paper revisits the concept of prebiotics, a term first defined as non-digestible food ingredients that selectively stimulate the growth and/or activity of beneficial bacteria in the colon, thus improving host health. The review explores methodologies for testing prebiotics, including the criteria needed for a food ingredient to be classified as a prebiotic. These criteria include resistance to gastric acidity, hydrolysis by mammalian enzymes, gastrointestinal absorption, fermentation by intestinal microflora, and the selective stimulation of beneficial bacteria such as bifidobacteria. The paper further reviews specific prebiotics, including inulin and trans-galactooligosaccharides (TOS), as well as the evidence supporting their classification.

Who was reviewed?

The review focused on the concept of prebiotics and the various studies, methodologies, and prebiotic candidates, such as inulin and trans-galactooligosaccharides (TOS), that have been tested for their potential health benefits. It also critically examined the existing body of literature regarding the criteria for classifying food ingredients as prebiotics, the methods used to demonstrate their effectiveness, and the microbial associations (such as bifidobacteria) that are impacted by prebiotic consumption. The review highlighted the limitations and gaps in current research, especially regarding the long-term effects and species-specific interactions of prebiotics with the gut microbiota.

What were the most important findings?

The review emphasizes that only two dietary non-digestible oligosaccharides, inulin and TOS, currently meet the criteria for prebiotic classification. The paper critiques the oversimplified “dose argument” often used in marketing prebiotics, asserting that the prebiotic effect is not determined solely by the amount ingested but by the composition of an individual’s gut microbiota before supplementation, particularly the number of bifidobacteria present. The study also introduces the “prebiotic index” as a more accurate measure of the prebiotic effect, which is the increase in the number of bifidobacteria relative to the daily dose of the prebiotic. Furthermore, the review identifies the significant role of gut microbiota in mediating the health benefits of prebiotics and notes that more research is needed to understand how prebiotics interact with gut bacteria at a species level, especially in relation to their potential in targeting specific bacteria like Clostridium coccoides–Eubacterium rectale cluster, which produces butyric acid and may have protective effects against diseases like colon cancer.

What are the greatest implications of this review?

The implications of this review are far-reaching, especially in the field of microbiome research and functional foods. It challenges the widespread commercial marketing of prebiotics, urging that consumers and regulatory bodies take a more scientific approach to their classification and use. The introduction of the prebiotic index could provide a more accurate and standardized way to evaluate prebiotics. Additionally, this review highlights the need for more in-depth research using advanced molecular microbiological techniques to better understand the specific bacteria affected by prebiotics and how this translates into health benefits. As our understanding of gut microbiota continues to evolve, there may be opportunities to tailor prebiotics to influence specific microorganisms and thus address particular health concerns, such as improving gut health or reducing the risk of colon cancer.