There is increasing awareness about the importance of the gut microbiome and bacteria balance for optimal digestive and whole body health. From researchers to health professionals to the general public – we are more aware of gut health than ever before. The star of this show, in recent years, has been the mighty probiotic supplement, with product companies loudly pushing their marketing message across TV and the Internet that probiotics are the answer to all of our gut health woes.
While probiotic supplements certainly have their place in the treatment of numerous digestive conditions, they really only make up one part of the picture when it comes to a healthy, balanced microbiome. To get the most out of the time, energy, and money you invest in your probiotic supplements and gut healing, it is important to understand the second, and arguably more important part of the picture – prebiotics.
Probiotics – the temporary tourists of the gut
It is a common misconception to think that taking a probiotic supplement will permanently populate your gut microbiome with the actual live bacteria in the supplement you swallow. The truth is, probiotic supplements only temporarily change the gut microbiome – once you cease supplementation, your gut microbiome eventually returns to its original state over days or weeks.
In this sense, probiotics act a little bit like tourists – they turn up, hang around for a little while, but ultimately, they are just passing through. They have numerous beneficial effects that are conducive to supporting a healthy microbiome while they are visiting, but eventually, they leave the gut via our stool.
It’s not uncommon for people to self-prescribe probiotics in an attempt to treat their gut symptoms, taking them for many months with no noticeable improvement. From here they conclude that probiotics ‘don’t work’, feeling frustrated and confused about what next steps to take.
There could be many reasons why probiotic supplementation didn’t have the impact you were promised by the claims on the bottle or the enticing advertisements, a primary one being a lack of concurrent prebiotic support in the gut.
Prebiotics – the fuel for our permanent gut residents
Prebiotics have a vital role to play in maintaining and promoting the health of the already existing bacteria in our gut. They are fibers that act as the primary fuel source for the bacteria of our microbiome, helping the good guys to flourish and multiply in number.
It is prebiotics who contribute most significantly to microbiome colonisation, not probiotics. Essentially, they are the lifeblood for the permanent residents of our gut.
If we have a thriving, healthy microbiome, the flow on effects of this are countless, including strong integrity of the gut lining, reduction of digestive discomfort, better immune defences in both the gut and whole body, enhanced nervous system function, and lower levels of inflammation.
The impact of prebiotic deprivation on gut health
There are a number of diets that have gained traction in recent years for their ability to provide symptomatic relief to those with chronic gut discomfort and functional digestive disorders, such as irritable bowel syndrome (IBS). These diets achieve this by virtue of being low in fermentable fibers. Since prebiotic fibre is a type of fermentable fibre, these diets are all low in prebiotics.
Perhaps the most well known of these diets is the low FODMAP diet, which was developed by researchers at Monash University for the treatment of IBS. Other diets include the Specific Carbohydrate Diet (SCD) and the Gut and Psychology Diet (GAPS diet).
Unfortunately, what many people on the low FODMAP diet are unaware of is that the diet was only ever intended for short-term use. Typically, it is not recommended for longer than 6-8 weeks. In reality, many people start the diet, notice immediate symptom relief, and then end up staying on it for many months, if not years. Sadly, this long-term deprivation of prebiotics has negative consequences for the microbiome.
Studies show that low FODMAP diets have the potential to reduce the number of beneficial bacteria, for example, Bifidobacterium spp., and may even allow the number of undesirable bacteria like Bilophila to grow. These impacts have been observed after only 4 weeks on the diet. For people with gut issues, this is bad news, as it will only further contribute to their gut dysfunction. Reactivity to prebiotic fibers often occurs due to large bowel dysbiosis or small intestinal bacterial overgrowth (SIBO), not because of an inherent FODMAP intolerance. Depriving the gut of prebiotics will only serve to worsen either of these conditions in the long run. The real answer to resolving symptoms lies in addressing the underlying cause, not following a restrictive diet that only provides temporary relief.
Prebiotics – how to get more of them in
Prebiotics are found in specific plant foods or we can also take prebiotic supplements to obtain therapeutic levels of the fibers we need. Prebiotics refers to a wide range of fibers, including fructooligosaccharides (FOS), galactooligosaccharies (GOS), and resistant starches. Other compounds found in foods also act like prebiotics, including polyphenols and prebiotic-like foods. Leading microbiome researcher and gut health specialist, Dr Jason Hawrelak, recommends that we eat a minimum of 40 different plant-based foods every week to meet our prebiotic needs and promote optimal microbiome diversity. Table I summarises the food sources of prebiotics.
Table I: Food sources of prebiotics
Fructooligosaccharides, oligo-fructans and inulin
Legumes – beans, lentils, chickpeas
Brassica family vegetables – broccoli, cabbage, brussel sprouts
Milk (lactose containing)
Legumes: red lentils, kidney & adzuki beans
Bananas – less ripe bananas have higher amount
Potatoes – cooked and then cooled (cooled for at least 6 hours)
Cassava and sweet potato
Rye sourdough bread
Oats – higher amounts in uncooked
Fruit: black elderberries, black currants, blueberries, cherries, strawberries, blackberries, plums, raspberries, apples (red), black grapes
Nuts & seeds: Flaxseed meal, chestnuts, hazelnuts, pecans, black tahini
Vegetables: purple carrots, red carrots, purple/red potatoes, red cabbage, spinach, red onions, broccoli, carrots (orange), red lettuce
Other foods: black olives and olive oil
Prebiotics for those who are sensitive to fermentable fibers
Eating more prebiotic-rich foods is easier said than done, especially if you are someone who is highly reactive to fermentable fibers. In this case, a slow and steady approach is vital, and often supplementation with a well-tolerated prebiotic is the best place to start. Partially hydrolysed guar gum (PHGG) is one of the best options for those sensitive to bloating and gas from fermentable fibers and has multiple beneficial effects for the microbiome that will get you started on the path to microbiome restoration.
When introducing any prebiotic fibre, start with a low dose and slowly increase the amount over a number of weeks to build tolerance. As the microbiome begins to restore and other factors are addressed, for example, SIBO or other overgrowths, other prebiotic supplements like GOS and FOS can be trialed and prebiotic foods can be introduced one by one in incremental doses, starting with your least reactive foods first and leaving the most reactive foods to last. This is a slow process and requires a lot of patience, but it is the best approach for restoring the microbiome in the long term.
Appreciating the role of prebiotics
So, next time you go to buy another bottle of expensive probiotics or before you conclude that probiotics haven’t worked for your symptoms, remember that they are only one piece of the gut health puzzle. To get the most bang for your buck and the best outcomes, make sure that you are placing equal (or maybe even more) importance on obtaining adequate prebiotic foods through your diet or supplementing with the right prebiotics for your gut.
Huaman, J.-W., Mego, M., Manichanh, C., Cañellas, N., Cañueto, D., Segurola, H., … Azpiroz, F. (2018). Effects of Prebiotics vs a Diet Low in FODMAPs in Patients With Functional Gut Disorders. Gastroenterology, 155(4), 1004–1007. https://doi.org/10.1053/j.gastro.2018.06.045
Staudacher, H. M., Lomer, M. C. E., Anderson, J. L., Barrett, J. S., Muir, J. G., Irving, P. M., & Whelan, K. (2012). Fermentable Carbohydrate Restriction Reduces Luminal Bifidobacteria and Gastrointestinal Symptoms in Patients with Irritable Bowel Syndrome. The Journal of Nutrition, 142(8), 1510–1518. https://doi.org/10.3945/jn.112.159285