The exciting possibilities of prebiotics for a variety of digestive, immune and mood related complaints are only just being discovered. Prebiotics are receiving more attention with the increasing understanding of the human microbiota (all of the bacteria, viruses and fungi that live on and in us), as the two together can have an incredible impact on our health.
What are prebiotics?
Essentially, prebiotics are ingredients found in whole, unprocessed vegetables, fruits, legumes, grains, nuts and seeds which are not digestible to us, but provide the perfect food for beneficial gut bugs living within us(1). These ingredients are broken down by the microorganisms in the digestive tract into compounds that have a beneficial effect in multiple areas of the human body, which can include altering the activity of the same bugs that created them! Most prebiotics are carbohydrate fibres, and it’s the knock-on effect of eating them that makes them so special.
How do they relate to probiotics?
I often hear prebiotics being confused with probiotics. While they act very similarly in the gut, they are in fact different. Probiotics are live organisms that we take in supplement form, where the species of bacteria are known and measured(2) Much like the gut bugs that have been living in us since the first few days of life (our microbiota), probiotics also love to munch on prebiotics. You will often find probiotics and prebiotics in combination in a supplement to enhance the products therapeutic quality. A lot of the research around prebiotics looks at how they interact with two of the most common probiotics, Lactobacilli and Bifidobacteria(3).
What’s the difference between fibre and prebiotics?
Most prebiotics are fibre, however not all fibres are prebiotic. Fibre is often classified as insoluble or soluble, which also provides a good basis for distinguishing which ones are prebiotic.
Insoluble fibres do not get broken down by us or by our gut bugs, however they do bulk out the stool, helping to keep us regular(4). These are the stringy fibres that give a lot of foods their rough texture, such as the skin of nuts, seeds, fruits and vegetables.
Soluble fibre, found in a variety of whole foods, cannot be broken down by us, but are easily fermented by bacteria. Those that exert a proven beneficial effect on us are termed prebiotics.
Types of prebiotics
Here is a little bit of extra information for the science lovers out there. A clear cut catagorisation of what is and what isn’t a prebiotic has not yet been established as it is still a young area of science. If we consider what has the potential for prebiotic activity, the following fibres and their respective foods are included:
- Non-starch polysaccharides such as beta-glucans (mushrooms), pectins (pear, apple, plum, citrus), gums (guar gum, xanthum gum), hemicellulose (psyllium husk) and cellulose (broccoli, cabbage, kale, cauliflower).
- Non-digestible oligosaccharides such as galactans (legumes) and fructans, primarily inulin (onion, garlic, artichoke, asparagus, leek, chicory root, banana).
- The disaccharide lactulose (only found in supplement form).
- Sugar alcohols including sorbitol (pears, plums, dried fruits) and mannitol (button mushrooms).
- Resistant starch, which is starch that resists digestion in the small intestine, making it available in the large intestine for fermentation (potatoes, legumes, whole grains).
How do prebiotics improve our health?
Prebiotics selectively stimulate the growth of beneficial bacteria that are indigenous to our guts, including the well-studied Bifidobacteria and Lactobacilli species. These bacteria, when thriving, help to seal the barrier between the intestine and bloodstream, improve our immunity and keep potential bad bacteria/fungi (such as clostridia and candida) to a minimum.(3). With a healthy microbiota, improvements are noted in mood, skin, allergies and autoimmune conditions, just to name a few.
In addition, bacteria create short chain fatty acids (e.g. butyrate, propionate and acetate) from prebiotic fibres, which have beneficial effects throughout the body. For example, butyrate, made by Lachnospiraceae and Ruminococcaceae bacteria, is a major energy source for the cells that make up our colon. Propionate acts at the liver to suppress cholesterol synthesis and acetate is utilised by the heart, brain, kidneys and muscles(1).
When prebiotics can be problematic
For people that have certain intestinal issues, such as Small Intestinal Bacterial Overgrowth (SIBO) or Irritable Bowel Syndrome (IBS), eating the wrong types of prebiotics can make symptoms worse. For example, fructans and sugar alcohols (which are both considered FODMAP foods) are known to cause bloating, flatulence and discomfort in certain people(5). However, complete avoidance of prebiotics deprives healthy gut bugs of food and can make the situation worse in the long run. If you fall into the SIBO or IBS, or are unsure, an appointment with us can help minimise symptoms while still making sure your good bugs are fed!
By Lucy Mason