Dr Bridgette Wilson, a gut specialist and clinical research dietitian, has carried out award-winning research into prebiotics in IBS. In this blog post, she explains what they are and whether or not people with IBS should take them.
Although VERY similar in name, prebiotics are not to be confused with probiotics, which are the actual live microbiota.
In their simplest definition prebiotics can be considered as food for good bacteria. The scientific definition of a prebiotic is substrates (usually fibres) that are selectively fermented by the (gut) microbiota and confer a health benefit to the host (us).
In popular culture, the term prebiotic is often applied to any food that contains fibres that bacteria could use as a food source, but this is not strictly a true use of the term.
Many foods may be considered to have prebiotic qualities due to the effect on the activity of the microbiota. For example, a high fibre diet feeds the gut microbiota and leads to a boost in anti-inflammatory butyric acid that feeds gut cells to keep them strong. However, fibre itself isn’t within the definition of a prebiotic because it generally isn’t ‘selectively fermented’.
In contrast, inulin-type fructans and galacto-oligosaccharides do fit the criteria for prebiotics and have been used in a wealth of human research to show that they can improve health in various ways.
Prebiotics act by increasing the kind of gut bacteria that we want to have more of, such as Bifidobacteria (often found within many probiotic foods). If you are living with IBS, statistically speaking you have lower Bifidobacteria than those without IBS, which is part of the theory for why prebiotics might be useful in IBS.
Prebiotics also drive an increase in acid production in the first part of the large bowel (colon) which helps to keep the pH at a level loved by our natural microbes and detested by invading pathogenic bacteria.
Research has further investigated the effect of prebiotics on the immune system and studies suggest that by interacting with mucosal immune receptor cells (the messengers between our gut and our immune system) prebiotics have an anti-inflammatory effect and can alter gene expression. This proof-of-concept research has so far been conducted in cells and in mice.
Studies in healthy adults have shown that prebiotic supplementation of the diet increases a compound called IgA, which is considered a protective immune indicator. A study in older adults (>65 years) showed that prebiotic supplementation, compared to placebo, led to a reduction in inflammatory markers in the blood.
So, what does this mean – should everyone take prebiotics?
In short, yes, we could all benefit from a healthy dose of prebiotic fibres. However, there are some things you should know if you have IBS to avoid increasing your symptoms with prebiotic consumption.
My research has focused a lot on the use of prebiotics in gut disorders including IBS and I have performed a systematic review and meta-analysis (combining data from numerous well designed studies) and found that unfortunately, if you have IBS then prebiotics that are inulin-type fructans (inulin, oligofructose, oligofructose) have no effect on abdominal pain or bloating but do seem to make flatulence worse!
All is not lost though as other types of prebiotics (galacto-oligosaccharides, partially hydrolysed guar gum, pectin) improved symptoms, specifically reducing the symptom of flatulence and showing a trend to reducing abdominal pain and bloating.
Interestingly, the types of prebiotics that seemed to make symptoms worse, would be classified as FODMAPs as they tend to be refined from high FODMAP food (such as chicory root), whereas the types of prebiotics that improved symptoms are not generally considered to be high in FODMAPs.
A second main finding from this research was that lower doses of prebiotics (less than 6 g/d) were better tolerated than higher doses (more than 6 g/d), so this means if you have IBS then having a small amount of prebiotic type fibre is more likely to be well tolerated than having too much. This may be linked to having fewer of the probiotic bacteria such as Bifidobacteria as it could mean that other bacteria have more chance of feasting on the prebiotic if there are less of the bacteria for whom it is intended.
In healthy adults who took a higher dose of a GOS type prebiotic, an increase in flatulence was reported for the first two weeks but by the end of week three this had reduced, indicating that there is an adaptation period to an increase in prebiotic fibre that may be overcome after three weeks of continued consumption.
Take home messages:
- Prebiotics increase Bifidobacteria in IBS. They also help maintain gut homeostasis through pH and immune regulation.
- Prebiotics made from galacto-oligosaccharides, partially hydrolysed guar gum or pectin are more likely to be tolerated if you have IBS.
- Any prebiotic is likely to be better tolerated at doses of less than 6 grams per day.
- Try prebiotics for at least three weeks to see if your gut can adapt to tolerate these.