Prebiotics for Health: What You Need to Know

Definition of prebiotics

The International scientific association for probiotics and prebiotics (ISAPP) define a prebiotic as “a substrate that is selectively consumed by host microorganisms offering health benefits” (ISAPP., 2018a). Prebiotics are typically indigestible carbohydrates, often soluble fibres, that serve as food for good bacteria that are present in the gut (ISAPP., 2018a). As prebiotics can change the makeup of the gut microbiome, this explains why they are a topic of interest when it comes to gut health.

The gut microbiome encompasses a diverse population of bacteria that perform a range of activities that can influence overall health (Al Bander et al., 2020). These include the metabolism of nutrients,immune system regulation and the body's natural defence against illnesses and infections (Al Bander et al., 2020).

How do prebiotics differ from probiotics?

Common gastrointestinal complaints reported in those with ASD, such as constipation, diarrhoea and abdominal pain, are associated with changes in the composition of the gut microbiome (Ristori et al., 2019). Many functional gastrointestinal disorders that feature these common issues have been linked to the gut microbiome and a lower abundance of beneficial bacteria, such as bifidobacteria (Ristori et al., 2019). Along with higher levels of Clostridiumbacteria, many children with ASD also have a lower relative abundance of bifidobacteria in the gut, suggesting a possible link between the gut microbiome and comorbidities of ASD (Argou-Cardozo and Zeidán-Chuliá., 2018; Ristori et al., 2019).

Children with ASD who also have comorbid gastrointestinal disturbances tend to exhibit more severe behavioural changes, such as irritability and social withdrawal, and these neurobehavioural symptoms are thought to have an underlying inflammatory pathophysiology (Fattorusso et al., 2019). The inflammation hypothesis in ASD suggests the presence of immune system dysfunction in its development (Hughes et al., 2022). Up to 80% of immune cells are found in the gut, and gut barrier function plays a key role in immune homeostasis (Wiertsema et al., 2021). Given that gut barrier integrity and function can be influenced by gut microbiome composition and crosstalk along the gut-brain axis, it is important to note that dysbiosis, such as what is seen in ASD, can lead to changes in immune system function (Erbescu et al., 2022; Levy et al., 2017).

What is the mechanism of action of prebiotics?

Upon reaching the lower gastrointestinal tract, prebiotics are fermented by beneficial bacteria. Both Bifidobacteria and Lactobacillus are key bacterial populations that are capable of utilising prebiotics, and as the beneficial bacteria grow in number, they can contribute to a more balanced gut microbiome (Holscher., 2017). Secondary metabolites, such as short-chain fatty acids (SCFAs), are produced by these beneficial bacteria when they ferment dietary prebiotics and they have been shown to play an important role in health. For example, they have been shown to support the integrity of the intestinal barrier by providing colonocytes with energy and influence metabolic processes such as glucose and lipid metabolism (Ferrari et al., 2022; You et al., 2022).

Types of prebiotics

Galactooligosaccharides

GOS are indigestible, galactose-containing oligosaccharides that are structurally similar to human milk oligosaccharides found abundantly in breast milk, and vary in their chemical structure depending on factors such as chain length (Mei et al., 2022). Research looking at GOS’s have demonstrated their capacity to have a positive effect on gastrointestinal, neurological and metabolic function due to their direct effect on the growth of beneficial bacteria (Mei et al., 2022).

GOS’s occur naturally in small quantities in certain foods such as legumes (beans and lentils), however, they are commonly added as a prebiotic ingredient to commercial supplements (Thornton., 2018). As one of the most extensively studied prebiotics in its category, our prebiotic ingredient, Bimuno GOS is shown to beneficially affect the human gut microbiome through its selective stimulation of bifidobacteria. Learn more about the science behind Bimuno here.

Fructooligosaccharides

FOS are made up of short fructose chains and exert a strong bifidogenic effect; the ability to target and feed bifidobacteria (Carlson et al., 2018). FOS is a plant-based prebiotic and can be found in foods such as artichokes, bananas, chicory, garlic, onion, and asparagus. (Sabater-Molina et al., 2009)

Inulin

Inulin is a fermentable dietary fibre comprising of fructan-type polysaccharides that are mostly derived from chicory root (Mensink et al., 2015). It is well established that inulin has a prebiotic effect and this has been demonstrated in both humans and animal models, with the most consistent effect being an increase in the growth of bifidobacteria, as well as an impact on host gene expression and metabolism (Tawfick et al., 2022). The main sources of inulin include Jerusalem artichoke, chicory, onion, garlic, barley, and dahlia (Segoviano., 2022). Of these, the roots and tubers of Jerusalem artichokes are frequently utilized as raw materials in the food industry to produce inulin (Qin et al., 2023).

The takeaway

Prebiotics are indigestible carbohydrates that act as a food source for beneficial bacteria in the gut. There are a number of types of prebiotics, many of which are derived naturally from food sources; however, they are commonly added into commercial supplements. Whilst research in the prebiotic category continues to grow, existing studies have shown benefits of microbiota modulation by prebiotics, including the growth of beneficial bacteria. As the microbes residing in the gut have been shown to play an important role in health, the inclusion of prebiotics could be an important addition to the diet to support a favourable gut microbiome balance.

By Amnah Ali, 2nd Year BSc Food Science and Nutrition student at Northumbria University

Completed as part of a work experience placement programme at Clasado

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