In our latest technical talk we examine prebiotics and human health, including common types of prebiotics, how they work , their advantages and current areas of scientific research.
The role of the gut in health and in particular its resident bacteria has received much attention over the last twenty years. However, awareness of the link between the gut and health actually goes back thousands of years. The ancient Greek physician Hippocrates with great foresight famously said, “all disease begins in the gut”. Even faecal transplants, something we think of as being a recent idea dates back over 1000 years to China.
The gut microbiome
The gut itself is estimated to contain more than 100 trillion individual bacteria comprised of 5000 different species1. They are involved in harvesting energy from food, manufacturing neurotransmitters such as serotonin and vitamins e.g. vitamin K and Vitamin B12 as well as modulating the immune system.
The so-called ‘good bacteria’ have been linked to improved health e.g. Bifidobacteria, while others, the ‘bad bacteria’ e.g. Clostridia, where present at elevated levels appear to be linked to ill health. A proliferation of these ‘bad bacteria’ over ‘good bacteria’ can create a state of gut dysbiosis (bacterial imbalance), linked to health problems as diverse as mental heath, obesity and infectious diseases2.
Various means are commonly used to modulate the balance and types of bacteria present in the gut including antibiotics, dietary control and the now widespread use of probiotics. Perhaps less well known is the use of prebiotics in human health, awareness of which is now rapidly growing.
What are prebiotics?
Prebiotics are defined as substances that are selectively utilised by host microorganisms conferring a health benefit3.
The concept of a ‘prebiotic’ was first put forward in 1995 by Gibson and Roberfriod in their scientific paper “Dietary modulation of the human colonic microbiota: Introducing the concept of prebiotics”.
Prebiotics are frequently equated with dietary fibre, but only a subset of dietary fibres qualify as prebiotics. Most prebiotics consist of specific carbohydrate polymers, although they can also include their various substrates as well as plant polyphenols.
Prebiotics in nature
Prebiotics are naturally present in breast milk in the form of human milk oligosaccharides (HMOs) and during the first few months of life they help to support the establishment of a healthy gut flora in the young infant.
Prebiotics are also present in some plant sources e.g. garlic, leeks, onions and chicory, although impractically large amounts of these in their whole form would need to be consumed to provide real benefit.
Consequently, most prebiotics are manufactured industrially for use in food supplements and foods including; fructooligosaccharides (FOS), galactooligosaccharides (GOS), mannanoligosaccharides (MOS) and beta-glucans.
These generally require an oral dose of at least 3 grams per day to confer a benefit, considerably less than the recommended level of dietary fibre, making them ideally suited for most food supplement formats.
How do prebiotics work?
Prebiotics specific polymeric structure allows them to resist digestion by endogenous gut enzymes in the small intestine. When they reach the large intestine they are selectively fermented and utilised by good gut bacteria. Here they serve as a preferred food source (liberating short chain fatty acids), which enables such bacteria to grow, multiply and flourish. The net effect is an increase in good bacteria at the expense of less preferred species of gut bacteria.
In simple terms they serve as a selective fertiliser for the flowers (good bacteria) over the weeds (bad bacteria) in the so called ‘gut garden’. This ability of prebiotics to modulate the gut microbiome (the ecosystem of microbes that live in the gut) is key to their role in human health.
Advantages of prebiotics
Prebiotics offer a number of advantages over their better know probiotic cousins not least of which is their ability to reach their main site of action (the lower gut) intact, whereas probiotics can have limited in-vitro stability.
Prebiotics are also far more stable in on-shelf storage situations and in food processing, being largely unaffected by temperature, humidity or oxygen, all of which limit the viability of probiotics. This makes prebiotics ideally suited to on-shelf food supplements, infant formula and a wide range of functional foods, including bakery products.
Probiotics also suffer from the uncertainty of knowing whether what is being administered is the best species or strain for the individual (in the absence of faecal testing and bacterial mapping), or indeed whether successful colonisation has even occurred.
Health benefits of prebiotics
When it comes to prebiotics and human health current scientific research is varied and diverse, often mirroring research on probiotics. This is perhaps not surprising given the gut microbiomes central role in many human systems.
Recent areas of prebiotic research include improving mental health i.e. depression and autism, metabolic syndrome, heart health, immune health and asthma. There is also the potential to enhance physical and athletic performance4.
As we look into the future and more light is shed on the complex interplay between the gut microbiome and the bodies systems we can expect the value of microbiome modulators, such as prebiotics, to garner increased recognition and become more widely adopted.
References
1. Impacts of gut bacteria on human health and disease. Int J Mol Sci. 2015 Apr 2;16(4):7493–7519.
https://pmc.ncbi.nlm.nih.gov/articles/PMC4425030
2. 20 things you didn’t know about the human microbiome; J Cardiovasc Nurs. 2014 Nov-Dec;29(6):479–481.
https://pmc.ncbi.nlm.nih.gov/articles/PMC4191858
3. Prebiotics: Definition Types, Sources, Mechanisms and clinical applications. Foods. 2019 Mar 9;8(3):92.
https://pmc.ncbi.nlm.nih.gov/articles/PMC6463098
4. Global Prebiotic Association. Prebiotic Type Spotlight: Athletic Performance Benefits. January 2025.