Prebiotics: What are they, what are the different types, and what is their future?

In 1995, Glenn Gibson and Marcel Roberfroid wrote the paper ‘Dietary modulation of the human colonic microbiota: introducing the concept of prebiotics​,’ introducing the world to the concept of prebiotics, which act as fuel for microorganisms living in the gut.

Nearly thirty years later, Gibson, who currently works as a professor at the University of Reading, is still at the centre of the field of probiotics and prebiotics. What does the Father of Prebiotics foresee for the future regulation of prebiotics and probiotics? And how is current research evolving? 

What are prebiotics?​

Prebiotics and probiotics are often used interchangeably, but they are in fact very different. While probiotics are live bacteria, prebiotics provide food for said bacteria.

“Prebiotics are more like fertilisers,” Gibson told FoodNavigator. “So they fortify the indigenous or the existing microbes, which is said to be beneficial in a particular ecosystem, and both pro and prebiotics have been most extensively researched in the gut.”

The different kinds of prebiotics​

There are two main types of prebiotic, according to Gibson: FOS (fructo-oligosaccharides) and GOS (galacto-oligosaccharides).

GOS is a synthetic prebiotic, the starting material of which is usually lactose. “An enzyme beta galactosidase or lactase ordinarily would digest lactose. But if you change the reaction conditions, it becomes a reversible enzyme, and so it builds it up and then oligosaccharide version of lactose is galacto-oligosaccharide. That’s the synthetic way of making GOS.” GOS is usually found in dairy products such as milk, cheese, yoghurt and butter, as well as legumes such as chickpeas and kidney beans.

FOS, which includes inulin, is both naturally occurring and synthetic. Sucrose can be made to develop FOS much like lactose can develop GOS, although FOS also appears in a range of fruit and vegetables, Gibson told us, such as bananas, artichoke, asparagus, onion and garlic. While it appears in a range of foods, an adult needs between four and five grams per day to elicit prebiotic affects.

There are others as well. “Others looked at: polydextrose, other oligosaccharides, maybe some dietary fibres, polyphenols; so there's a wider array of prebiotics than was originally the case.”

One apparent dividing line between prebiotics, how they are ingested, does not actually make much difference in terms of their affect. While some prebiotics are found in food and others in supplements, the difference isn’t significant, according to Gibson, because “the active ingredient is the same.”

For example, “one really big area for prebiotics is infant formula because breast milk has a ligousaccharides in it. It's a very good natural prebiotic. They try to replicate some of the microbiological effects of breast milk. Formula feed manufacturers are using prebiotics and that looks good in terms of reducing rates of infections and the atopic issues like asthma.

“The thing about prebiotics is you can you can throw anything at them. So you can heat them; dryness doesn't matter because they're inert, they're not living ingredients, and so they're resistant to a lot of food processing aspects.

“You see quite a wide variety of foods that prebiotics appear in, which probiotics really don't like baked products, breads, cereals for instance.

“Using a supplement is moving towards a pharma type approach and I wonder whether generally consumers prefer to have active ingredients in foods, which you know at least are ostensibly healthy already, but I don't think biologically there's too much as long as the active ingredient is active and remains so.”

The future of prebiotics and probiotics in regulation​

According to Gibson, there is a wealth of research on probiotics and prebiotics (around 45,000 papers on the former, 15,000 on the latter). However, despite the abundance of research available, the health claims have not surfaced in law.

“The health claims have not really materialised from all of that body of evidence, and I don't really know why, particularly in Europe,” Gibson told us.

“The Food Safety Authority (FSA) have turned down the vast majority of what has been submitted, and I don't really understand the reasoning for that, apart from some kind of argument that cause and effect is not definitively proven, which is actually pretty impossible to prove for anything, including a lot of most pharmaceuticals.

“So I think one way or another, I won't really be convinced that within 60,000 research publications, there aren't a whole load of claims in there somewhere.”

It is important, he suggested, for consumers to have information available, backed by research, to help them understand which products to choose. “If you know you're a consumer who's not familiar with the field but wants to try it out, you need readily accessible information to sort out which products are preferable to others; which ones have been tested independently in a reproducible manner.

“At the moment, if you go in a supermarket or a health food store, it's a level playing field. The ones that have no research behind them are equally available as the ones that have, and it's very difficult to really separate these, but they need to be separated because we should only really trust the products that have been validated.”

However, he predicts that his native UK may come up with a regulation on prebiotics and probiotics in the foreseeable future.

What does current prebiotic research focus on?​

According to Gibson, the main area of research in prebiotics (and probiotics) at the moment is COVID-19.

“You look at what's happened since COVID; there's a pile of papers on gut health and COVID and trying to decrease inflammation from the virus, trying to stop the virus binding, trying to look at its effect on the microbiome, and definitely pro and prebiotic interventions have come into that field in a big way.

“It's trying to improve protection, if you get COVID, to try and fortify natural defence; but also the long COVID, which is characterised by inflammation. We know that pro and prebiotics, if they're any good, can dampen inflammation in some cases, and so the use of them to counteract some of the viral symptoms is to me a no brainer because if probiotics and probiotics are as safe as we believe they are you know it seems a rational thing to do.”

The more general trend, he told us, is “looking at the emerging pathogens, I think the story's going to be kind of the same. What do we do to improve gut health that might have a systemic effect on something like a respiratory virus?”