Probiotics, Prebiotics and Fibre: What's the Difference?
The terms probiotics, prebiotics and fibre are often used interchangeably in conversations about gut health, but they each serve very different purposes. Understanding these differences is especially important for people managing medically diagnosed IBS or other gastrointestinal conditions, where the wrong approach can sometimes worsen symptoms rather than improve them.
This blog explores what each of these terms really means, how they function, and how they fit into a broader gut health strategy.
Probiotics: Targeted Support for Specific Symptoms
Probiotics are live microorganisms that, when taken in adequate amounts, may offer health benefits. Their value lies in strain-specific effects, meaning not all probiotics have the same impact. While many probiotic products are marketed broadly for "gut health," only a handful of strains have demonstrated benefit in people with medically diagnosed IBS and other gastrointestinal conditions.
Two of the most studied strains for medically diagnosed IBS include:
Lactobacillus plantarum 299v Some research suggests this strain may help relieve abdominal bloating and abdominal discomfort, and support regular bowel habits in people with medically diagnosed IBS.
Lactobacillus rhamnosus GG One of the most well-studied probiotic strains in the world, with evidence suggesting it may help manage certain gastrointestinal symptoms and support digestive health. Some research suggests it may be particularly helpful for people with medically diagnosed IBS.
It is important to note that probiotics are typically used for symptom management rather than to broadly improve gut microbial diversity. While some people experience relief with probiotic use, others may not see any noticeable change. These products are best used with a specific purpose in mind.
Prebiotics: Fuel for Beneficial Gut Bacteria
Prebiotics are a type of fermentable fibre that serve as food for the bacteria already residing in your gut. When consumed regularly, they can help promote a more diverse and balanced microbiome, which is associated with a number of digestive health benefits.
Common dietary sources of prebiotics include:
- Oats
- Garlic and onions
- Leeks and asparagus
- Legumes and lentils
- Green bananas
However, many prebiotic-rich foods are also high in fermentable carbohydrates known as FODMAPs. These compounds can trigger symptoms in people with a sensitive gut or medically diagnosed IBS, including bloating, pain, and altered bowel habits. For this reason, the reintroduction of prebiotic foods is often best done with the guidance of a dietitian trained in gastrointestinal conditions.
It's also worth noting that some probiotic products contain prebiotic excipients like inulin. For people with medically diagnosed IBS who are sensitive to fermentable fibres, this is worth checking on the product label before use.
Fibre: Structural Support for Digestion
Fibre is the indigestible component of plant foods that plays a fundamental role in digestive health. It helps regulate bowel movements, and in some cases, can influence microbial balance.
Fibre can be categorised in various ways, including:
- Soluble vs insoluble: Soluble fibres dissolve in water and may help with stool formation, while insoluble fibres add bulk to the stool and assist with transit
- Fermentable vs non-fermentable: Fermentable fibres are broken down by gut bacteria, producing gases that can contribute to bloating. Non-fermentable fibres pass through the gut largely unchanged and are generally well tolerated
One particularly well-tolerated fibre for people with a sensitive gut is sterculia. This non-fermentable, water-absorbing fibre softens hard stools and adds bulk to loose ones, helping to support stool consistency and ease of passage. Unlike fermentable fibres, it is generally well tolerated and gentle on the digestive system, making it a helpful option for those who experience bloating or discomfort.
How Do They Fit Together?
These three components each have a role to play, but they serve different purposes:
- Probiotics offer targeted symptom management for select conditions, particularly when the right strain is chosen. For people with medically diagnosed IBS, certain strains may help relieve digestive discomfort and reduce the occurrence of symptoms
- Prebiotics promote long-term microbial diversity, though they may need to be introduced cautiously in people with sensitive guts or medically diagnosed IBS
- Fibre supports the structure and function of the digestive system, with different types better suited to different needs
For example, someone managing medically diagnosed IBS might begin with non-fermentable fibre to help support regularity and consistency. If symptoms remain, they might trial a probiotic strain with evidence for relieving abdominal bloating and discomfort associated with medically diagnosed IBS. Later, under the guidance of a dietitian, they may start reintroducing prebiotic foods to support microbial diversity.
The Takeaway
Understanding the difference between probiotics, prebiotics and fibre allows you to make more informed decisions about what your gut actually needs. There is no single solution that works for everyone, and more is not always better.
If you are experiencing persistent symptoms or are unsure where to begin, consult a gastroenterologist or gut-trained dietitian. A tailored approach will always outperform a generic one when it comes to supporting your gut health. And if symptoms persist, worsen, or episodes become more frequent, speak with your medical practitioner.
Important Information: Always read the label and follow the directions for use. If symptoms persist, talk to your health professional. If symptoms persist, worsen or episodes become more frequent, talk to your medical practitioner. Always drink plenty of water when taking this product. Do not use when abdominal pain, nausea or vomiting are present or if you develop diarrhoea. If you are pregnant or breastfeeding, seek the advice of a healthcare professional before taking this product.