Prebiotics and probiotics work hand in hand to support a healthy gut. While probiotics provide beneficial bacteria, prebiotics provide the nourishment these bacteria need to grow and thrive. Whilst there is a lot of information around on probiotics there is less about prebiotics; so what are they?.
What are Prebiotics?
Prebiotics are not live organisms like probiotics, but types of plant fibre that pass through the digestive system largely undigested until they reach the large intestine. Here, they are fermented (broken down) by gut bacteria and used as a food source by beneficial microbes, helping them to grow and thrive and supporting a healthy, balanced gut microbiome. In this way, prebiotics help create the right environment for beneficial bacteria, including probiotics to flourish.
This fermentation produces beneficial compounds called short-chain fatty acids (SCFAs), including butyrate, acetate and propionate. These help nourish the cells lining the gut, support the integrity of the intestinal barrier, maintain a healthy gut environment, support immune function and help regulate inflammation. Butyrate is particularly important, as it is a key energy source for the cells lining the colon and helps support a strong, healthy gut barrier.
Prebiotics are often combined with probiotics in supplements. While probiotics introduce beneficial microorganisms, prebiotics provide the food that helps beneficial bacteria already within the gut to thrive.
Understanding Fibre: What Makes a Fibre Prebiotic?
Fibre plays an important role in digestive and gut health, but not all dietary fibre acts as a prebiotic. Fibre is commonly described as either soluble or insoluble, depending on how it behaves in water, although there can be some overlap between the two.
- Insoluble fibre does not dissolve in water and is generally less fermentable by gut bacteria. Instead, it passes through the digestive tract largely intact, adding bulk to the stool and helping to support normal intestinal movement and regular bowel function. Cellulose, a structural component of plant cell walls found in foods such as vegetables and the outer layers of grains and seeds, is a common example. Most insoluble fibres are poorly fermented and are not generally considered prebiotic. Insoluble fibre however can be very helpful in certain situations, such as constipation, helping to move a stool through the GI system, and ultimately supporting overall bowel health
- Soluble fibre dissolves in water and can form a gel-like substance within the digestive tract. Many soluble fibres are also fermentable, meaning that when they reach the large intestine they can be broken down by gut bacteria and used as a food source. However, not all soluble or fermentable fibres are necessarily prebiotics.
It is useful to distinguish solubility from fermentability. Whether a fibre dissolves in water does not necessarily tell us how readily it will be fermented by gut bacteria. Equally, being fermentable alone does not automatically mean that a fibre qualifies as a prebiotic.
So, what makes a fibre prebiotic?
A prebiotic is a substance that is selectively used by microorganisms in the body in a way that provides a health benefit. In simple terms, prebiotics provide nourishment for particular beneficial microbes, helping to encourage their growth and activity and supporting a healthy, balanced gut microbial community.
As prebiotic and other fermentable fibres are broken down by bacteria in the large intestine, they can produce beneficial compounds called short-chain fatty acids (SCFAs). The three main SCFAs are acetate, propionate and butyrate.
These compounds have several important roles within the gut. Butyrate, in particular, is an important energy source for the cells lining the colon (colonocytes) and helps support the integrity of the intestinal barrier. SCFAs also contribute to a healthy intestinal environment and play a role in communication between the gut microbiota, intestinal cells and immune system.
So, prebiotic fibres don't simply contribute to digestion and stool quality. By providing a food source for selected gut microbes and influencing the compounds they produce, they can also help support the wider health of the gut microbiome.
Common prebiotic fibres and carbohydrates
Some of the best-known prebiotic fibres and carbohydrates are detailed below. FOS, GOS and inulin-type fructans are among the most extensively studied, while research continues into a much wider range of fibres and other compounds with potential prebiotic effects.
- Fructo-oligosaccharides (FOS) – short-chain carbohydrates made predominantly from fructose molecules. They occur naturally in a variety of plant foods and are readily fermented by certain gut bacteria.
- Mannan-oligosaccharides (MOS) – complex carbohydrates commonly derived from the cell walls of the yeast Saccharomyces cerevisiae. MOS are frequently included in dog foods and digestive supplements, although their effects and mechanisms differ somewhat from those of more traditionally recognised prebiotics such as FOS and GOS.
- Galacto-oligosaccharides (GOS) – non-digestible carbohydrates commonly produced from lactose. They pass through the upper digestive tract largely undigested before reaching the large intestine, where they can be utilised by gut bacteria, particularly Bifidobacterium species.
- Inulin – a naturally occurring fermentable fibre and type of fructan found in plants including chicory root, Jerusalem artichoke and dandelion root. It passes largely undigested into the large intestine, where it can be fermented by gut bacteria.
So what foods can I give to my dog that contain prebiotics?
A number of foods naturally contain prebiotic fibres with examples of prebiotics including:-
Functional Mushrooms
Mushrooms such as Turkey Tail, Reishi, Chaga, Lion's Main and Maitake are provide a valuable source of prebiotic compounds, including complex carbohydrates and polysaccharides such as beta-glucans, chitin, mannans, xylans and galactans. These compounds resist digestion higher up the digestive tract and can be utilised by microorganisms in the large intestine, helping to support a healthy and diverse gut microbiome. Research suggests that mushroom polysaccharides can help encourage beneficial gut bacteria and influence the overall composition of the microbiome. Different mushroom species contain slightly different combinations of these compounds, which is another reason why a variety may be beneficial. Studies have investigated their effects on gut bacteria, with species such as Reishi associated with increases in beneficial bacteria including Lactobacillus and Bifidobacterium, while Turkey Tail and Chaga have also demonstrated microbiome-modulating properties.
Mushrooms have many other potentially beneficial compounds and are widely researched for their wider effects on immune health, inflammation and general wellbeing, but from a prebiotic perspective, it is their complex polysaccharides that make them particularly interesting for supporting the gut microbiome.
Garlic
Garlic (crushed or chopped) is a natural source of prebiotic fibres, including inulin and fructooligosaccharides (FOS), which can provide a food source for beneficial bacteria within the gut. Garlic is safe in small amounts and you can find more abour garlic by reading our blog - Mythbusting: Is Garlic Safe for Dogs?
Seaweed
Seaweed is a valuable natural prebiotic for dogs because it contains fermentable polysaccharides and fibres, including alginates, fucoidan and laminarin a type of beta-glucan, which can provide a food source for beneficial gut bacteria and help support a diverse and balanced gut microbiome.
Green Tripe
Green tripe can provide prebiotic support because it contains naturally occurring fermentable fibres and nutrients that help nourish beneficial gut bacteria and support a healthy, diverse microbiome.
Fermented Foods
Fermented Foods such as fermented (onion-free) vegetables such as sauerkraut or fermented sheep / goat milk such as unsweetened kefir (although some dogs can have a lactose intolerance, in which case use water kefir). Note, if your dog has a yeast problem do not feed fermented food until the yeast is under control as this will feed the yeast in your dogs’ intestines.
Other Prebiotic Fibres & Ingredients to Look Out For
As well as naturally prebiotic foods, there are several specific prebiotic fibres and ingredients that you may see listed in pet foods and supplements.
Fructooligosaccharides (FOS) – fermentable prebiotic carbohydrates found naturally in foods such as chicory root, Jerusalem artichoke, asparagus, bananas and small amounts of crushed garlic.
Inulin – often extracted from chicory root, is a commonly used source of fructans with prebiotic activity and is used in pet foods and supplements. Dandelion and Burdock are also high in inulin.
Mannan-oligosaccharides (MOS) – commonly obtained from the cell walls of the yeast Saccharomyces cerevisiae and frequently included in pet foods and digestive supplements.
Larch arabinogalactan – a fermentable fibre obtained from the larch tree that can be utilised by beneficial bacteria within the gut and is sometimes included in supplements as a prebiotic.
Other plant-based sources – you don't necessarily need to look for specialist ingredients to add a little more variety to your dog's diet. Cruciferous vegetables such as broccoli and kale; green beans and carrots, and fruits such as apples (with skin, no core) and berries, provide a mixture of fibres and plant compounds that can help nourish the gut microbiome. Dandelion root and burdock root are other useful sources of fermentable fibres and are sometimes found in pet foods and supplements. Dandelion and Burdock can be purchased as a dried herb, tea or tincture.
Including a variety of suitable plant foods can provide different types of fibre, giving the diverse populations of bacteria within the gut a broader range of substrates to ferment.
You may find your dog prefers one or two choices over others. Consume diverse types of Prebiotic Fibre - Your gut loves prebiotics.
And finally feeding prebiotics with probiotics keeps your dog's gut bacteria at its healthiest.....which also means a stronger immune system!
Many of our probiotic supplements contain prebiotics and you can view the range here. We also sell a prebiotic supplement PetBiome Prebiotic with inulin, kelp, hemp, wheatbran and cyanosis.
