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Prebiotics: What are they and how can they benefit our health?

A selection of hands holding a gut diagram
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The gastrointestinal tract is one of the most complex systems in the human body, home to trillions of bacteria, fungi and other microorganisms. But to keep our gut health in check, we need to include prebiotics in our diets.

“Prebiotics are a special type of fiber that humans can’t digest but our gut bacteria can, so they feed the good bacteria in the gut and thereby support digestive health,” explains Dr Michelle Braude, medical doctor, nutritionist and founder of The Food Effect (opens in new tab)

Knowing the links between nutrition and gut health can have a significant impact on your overall health. Here, we’ll look more in-depth at what prebiotics are, how they work and – most importantly – where you can find them in your diet.

What are prebiotics?

‘Probiotics’ and ‘prebiotics’ may sound similar, but many people don’t know the difference between the two. “They’re both beneficial for our gut health, but they work in different ways,” says Braude. “Probiotics are good bacteria found in certain foods or supplements. So when we eat these foods or take probiotic supplements we’re populating our gut with beneficial bacteria. These microbes then use prebiotics as food so they can thrive and grow in numbers – it’s like fertilizer for our friendly bacteria.”

Research (opens in new tab) suggests that the composition and function of your gut microbiota is a direct reflection of your genetic make-up and current lifestyle and as such, changes constantly. In fact, any alterations to your diet can modify the structure of your microbiome within 24 hours (opens in new tab). If these changes are highly beneficial to your health, the foods or particular nutrients that triggered these changes can be classed as prebiotics.    

“There are a wide variety of natural food sources available that contain probiotics and prebiotics, and also many good quality supplements,” Braude. “Foods that are high in prebiotic fiber include Jerusalem artichoke, asparagus, garlic, onion leeks, beans and pulses.” 

You can read more about prebiotics vs probiotics for a deep dive into the differences between the two.

How do prebiotics work?

The unique properties of prebiotic foods come from specific nutrients such as dietary fiber and other components that the human body is not able to digest fully. They move through your digestive system largely intact and, when they reach the intestines, these prebiotics are metabolized by the residing microbes. This process generates what are known as biologically active end products (opens in new tab) that have a direct impact on our physiology, including short-chain fatty acids (SCFAs) acetate, propionate, and butyrate. 

prebiotic food

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“The short chain fatty acids inhibit the growth of harmful bacteria as well as helping to regulate electrolyte balances in the body which are also important for good digestion and bowel movement,” explains Jackie Hodson, co-founder of The Gut Reset Bootcamp (opens in new tab)

What types of prebiotics are there?

Inulin is a type of dietary fiber that generates particularly large quantities of short-chain fatty acids. Multiple studies (opens in new tab) have reported the beneficial impact of inulin on digestive health, particularly in relation to chronic constipation. There’s also evidence (opens in new tab) that this nutrient may lower cholesterol levels, regulate blood sugar, improve immune responses and enhance the absorption of minerals.     

Fructooligosaccharides and oligosaccharides are complex carbohydrates that are largely resistant to human digestive enzymes and can have a big impact on our health and wellbeing. Humans encounter them very early on, with newborn babies getting a dose of these prebiotics in their mother’s breast milk. In fact, the amount of oligosaccharides present in human milk is greater than the amount of protein. It’s a key component in forming a baby’s immunity to pathogens and response to inflammation.

Research (opens in new tab) suggests that oligosaccharides form a strong line of defense against multiple different pathogens. For example, they can prevent and treat infections by disrupting the life cycle of harmful bacteria and stopping them from replicating in your body. They can also have beneficial effects on our metabolism and can be particularly helpful for treating type 2 diabetes.

What are the benefits of prebiotics?

Prebiotics have a particularly beneficial effect on various gastrointestinal issues, including irritable bowel syndrome (IBS), chronic idiopathic constipation (CIC), bloating and diarrhea. IBS is a common chronic condition that affects up to 21% of the general population (opens in new tab). There isn’t a single effective treatment for IBS, but evidence (opens in new tab) suggests that poor gut health plays a major role in the development and so prebiotics may be effective in reducing the severity of symptoms.  

You can read more about the importance of gut health and why it is important.

woman with ibs on her sofa

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Similarly, studies (opens in new tab) have shown that prebiotics may be highly effective for treating CIC and several types of diarrhea. They may improve stool consistency and number of bowel movements, as well as reduce bloating.

When it comes to weight management, there is mounting evidence (opens in new tab) that prebiotics could help to address obesity and corresponding metabolic disorders. Individuals with a normal body mass index tend to have a different set of gut microbes to those who suffer from obesity. Modifying the gut microbiota with the right prebiotics could pose as an effective complementary therapy for people who struggle with weight loss.

Evidence (opens in new tab) also suggests that the communication between our brain and gut microbes may play a significant role in mental health. However, evidence from clinical trials investigating the link between depression, anxiety and the use of prebiotics is mixed and more studies are needed to establish the nature of this connection. You can read more about and the role the gut brain axis plays in overall health.   

How to eat more prebiotics

What happens in our gut will have an impact on our entire body. Every year brings new evidence about the importance of keeping our gut health in check, so adding prebiotics to our diet can be a great way to keep our guts in good working order.

To get the most benefit, we need to ensure that we include multiple different types of prebiotics in our diets. “One key thing to remember is that the bacteria follows the diet, not the other way around so diversity is important,” says Hodson. “If you eat poorly, the bad bacteria will increase, and then you are at risk of dysbiosis which is an overgrowth of pathogenic organisms in the gut.”

Anna Gora
Health Writer

Anna Gora is a Health Writer for Future Plc, working across Coach, Fit&Well, LiveScience, T3, TechRadar and Tom's Guide. She is a certified personal trainer, nutritionist and health coach with nearly 10 years of professional experience. Anna holds a BSc degree in Nutrition from the Warsaw University of Life Sciences, a Master’s degree in Nutrition, Physical Activity & Public Health from the University of Bristol, as well as various health coaching certificates. She is passionate about empowering people to live a healthy lifestyle and promoting the benefits of a plant-based diet.