The vast colony of microbes within our gut – commonly referred to as the microbiome – is a hugely important ecosystem consisting of trillions of bacteria, viruses, fungi and other microorganisms. Emerging research indicates these may play a role in influencing both our physical and mental health, affecting different body systems such as the immune and nervous systems and potentially influencing wider metabolic health and weight control.
Yet for the most beneficial species within the gut to survive and thrive, they require the right kinds of fuel, and in particular certain carbohydrates and plant fibres found within many fruits, vegetables, nuts and seeds, known as prebiotics. While you might already be aware of probiotics, the two terms could not be more different.
“Probiotics are live microorganisms that have a beneficial impact on health when you consume enough of them,” says Dr Lucy McCann, a nutrition expert and honorary clinical research fellow at Queen Mary University of London. “Prebiotics, on the other hand, are foods that feed your beneficial gut microbes and improve their growth or boost their activity.”
To increase the number of prebiotics in your diet, McCann emphasises eating a diverse range of fibre-containing foods, something that is typically lacking in the average UK diet – just 9% of adults consume the recommended daily intake of fibre.
“We should aim to eat about 30 different plants a week to get a diverse range of prebiotics,” says McCann. “Eating wholefoods is also important as the skin of fruit and vegetables contain a lot of fibre. You can also make simple swaps that will dramatically improve your gut health. For instance, [just] switching white rice to pearl barley in a recipe will increase the fibre you consume almost tenfold.”
With research demonstrating that our individual gut needs are all unique due to the large variations in microbial populations from one person to another – even identical twins only share about a third of their microbiome species, McCann recommends booking an appointment with an independent nutritionist to discuss your own prebiotic needs. “This is especially advised if you have specific health needs or conditions such as IBS,” she adds.
Until 7 February, you can do just that, for free, with Holland & Barrett. The health food store is offering 45-minute online appointments with qualified nutritionists who can help you begin to understand your unique gut, and develop a science-backed, gut-health plan that’s tailored to you. Follow up with a trip in-store where specially trained staff can offer advice on products to complement what you learn from your nutritionist.
But what is it that’s inside the plants we eat that feeds our biome? The most well-researched prebiotics, according to University of Reading microbiology professor Glenn Gibson, who has been studying the microbiome for more than 30 years, are plant sugars called fructo-oligosaccharides (FOS) and galacto-oligosaccharides (GOS), which occur naturally within plants such as onions, chicory, garlic, asparagus, bananas, artichokes, lentils and chickpeas. Instead of being broken down and digested within the stomach, FOS, GOS and other prebiotics pass directly into the colon where they are fermented by bacteria that use this fuel to produce useful chemicals or metabolites.
Both FOS and GOS are known to nourish one of the most critical bacterial populations in the gut, namely Bifidobacteria (y-shaped bacteria that secrete B vitamins) as well as healthy fatty acids which are thought to have a protective effect against weight gain and a range of inflammatory diseases.
“Prebiotics act by modulating the [gut] microbiota towards a more beneficial community,” says Gibson. “This helps reduce pathogens as well as having anti-inflammatory and immune-boosting effects.”
Two of the most beneficial compounds produced by gut bacteria as a consequence of fermenting prebiotics, are butyrate and propionate. Because these chemicals act to reduce inflammation in the colon as well as protecting the gut wall, they are among the main reasons that prebiotics are thought to have a beneficial role for gut disorders such as inflammatory bowel disease and irritable bowel syndrome (IBS).
Because of the connection between the gut and the brain through pathways such as the vagus nerve – the long bundle of nerve fibres that stretches from the brain to the abdomen – as well as the bloodstream, there is increasing evidence that consuming sufficient prebiotics may help modulate your mood and your appetite. In September 2023, a new study (pdf) from researchers at the University of Leipzig Medical Centre found that participants who consumed high daily doses of a prebiotic called inulin – which is found naturally in garlic, bananas and onions – showed less activation in areas of the brain in response to high-caloric foods.
“Some metabolites from gut bacteria are known to affect cognitive processes and can be transported to the brain,” says Gibson. “There are several examples being researched in the context of mental health as well as appetite regulation and satiety.” Research in this field may lead to better understanding about appetite and may even open up new interventions to support weight control in the future.
Meanwhile, researchers are investigating how future prebiotic supplements could be designed with the idea of stimulating specific healthy microbes such as the yeast Saccharomyces, which has the ability to adhere to harmful bacteria such as E coli and salmonella and help remove them from the body.
“Some prebiotics may be developed in the future for Saccharomyces,” says Gibson. “We may [also] be able to develop new types to fortify other health-positive bacteria that can achieve different goals to Bifidobacteria.”
For a science-backed gut-health plan that’s tailored to you, book a free 45-minute online appointment with one of our qualified, professional nutritionists at hollandandbarrett.com. (For a limited time, normally £45)
Terms and conditions: Appointments are online only and are subject to availability. For full terms and conditions visit hollandandbarrett.com
