If you've read our other articles, you already know the headline: prebiotic fibre feeds the bacteria in your gut, and those bacteria pay you back. This article is about what they pay you back with.
The single most important thing your gut bacteria make for you is a short-chain fatty acid called butyrate. It's not something you eat directly in any meaningful amount. It's something you grow, inside your own colon, by feeding the right bacteria the right fibre. And one of the best fibres for the job happens to be the resistant starch in Mr. Regular +Prebiotic: Solnul®.
Here's how that works, and why it matters well beyond your gut.
Meet butyrate, the fuel your colon runs on
Your large intestine is lined with cells called colonocytes. Unlike most cells in your body, which run primarily on glucose, colonocytes have an unusual preference: their favourite fuel is butyrate. In fact, butyrate provides roughly 70 to 80% of a colonocyte's energy (Parada Venegas et al., Frontiers in Immunology, 2019).
That's a strange and telling arrangement. The cells lining your gut have effectively outsourced their energy supply to the bacteria living next door. Feed the bacteria well, and they keep your gut lining fed and functioning. Starve them, and the lining is one of the first things to suffer.
So butyrate isn't a trendy supplement buzzword. It's the basic currency that keeps the wall between your gut contents and the rest of your body healthy.
You don't eat butyrate. You grow it.
Here's the part most people miss. You can't meaningfully top up your butyrate by eating it. There are trace amounts in butter (that's where the name comes from — butyrum is Latin for butter), but nowhere near enough to matter, and it wouldn't survive the trip to your colon anyway.
The only reliable way to raise butyrate is to give the bacteria in your colon the fibre they ferment to make it. When gut bacteria break down prebiotic fibre, they produce three main short-chain fatty acids: acetate, propionate, and butyrate. Of the three, butyrate is the one your gut lining is hungriest for.
Which brings us to the specific fibre that's especially good at producing it.
The resistant starch connection
Most starch — the kind in white bread, pasta, or a regular boiled potato — gets broken down into sugar in your small intestine and absorbed before it ever reaches your colon. Your gut bacteria never see it.
Resistant starch is different. As the name says, it resists digestion. It passes through the small intestine intact and arrives in the colon still whole, which is exactly where your fibre-fermenting bacteria are waiting.
Solnul®, the resistant starch in Mr. Regular +Prebiotic, is a type called RS2 — intact, native starch granules made from upcycled Canadian potatoes. RS2 is one of the most concentrated forms of resistant starch found in nature, and it's a well-documented raw material for short-chain fatty acid production once it reaches the colon (Teichmann & Cockburn, Frontiers in Microbiology, 2021).
In Solnul's own randomized, placebo-controlled clinical trial, just 3.5 grams a day for four weeks significantly increased beneficial Bifidobacterium and Akkermansia, and reduced both constipation- and diarrhea-associated bowel movements compared to placebo (Bush et al., Nutrients, 2023). That low dose matters: most resistant starches need 10–20 grams a day to do anything measurable. (More on how the fibres in Mr. Regular are chosen on our science page.)
How a potato starch turns into butyrate
This is the genuinely interesting part, and it explains why a blend of prebiotics tends to beat any single fibre.
Almost no single bacterium does the whole job alone. Making butyrate from resistant starch is a relay, not a solo sprint:
Leg one — the breakers. A small number of specialist bacteria (most famously Ruminococcus bromii) are able to grab onto resistant starch granules and break them apart. Very few microbes can do this, which is why these "keystone" species matter so much.
Leg two — the fermenters. The bacteria that Solnul has been shown to boost, like Bifidobacterium, feed on the breakdown products and ferment them into acetate and lactate.
Leg three — the butyrate makers. Dedicated butyrate producers such as Faecalibacterium prausnitzii and Roseburia then take that acetate and lactate and convert it into butyrate. This hand-off is called cross-feeding, and it's been directly demonstrated in the lab: when Bifidobacterium and butyrate-producing gut bacteria grow together, butyrate output rises beyond what either makes alone (Belenguer et al., Applied and Environmental Microbiology, 2006).
So when Solnul raises your Bifidobacterium, it isn't just adding "good bacteria" for their own sake — it's stocking the relay team that ultimately delivers butyrate to your gut lining. (This is also the difference between a prebiotic and a probiotic — we explain it here.)
What butyrate actually does for you
Once it's made, butyrate does a lot more than feed colonocytes. Here's the short version of a long body of research (Parada Venegas et al., Frontiers in Immunology, 2019):
| What butyrate does | Why it matters |
|---|---|
| Fuels colonocytes | Provides 70–80% of the energy your gut-lining cells need |
| Strengthens the gut barrier | Tightens the junctions between cells and supports the protective mucus layer |
| Calms inflammation | Lowers pro-inflammatory signals (like IL-6 and IL-12) and helps keep the immune system balanced |
| Supports antimicrobial defence | Helps your gut produce its own antimicrobial peptides |
| Signals beyond the gut | Acts as a messenger molecule (via HDAC inhibition and GPCRs) that the immune system and gut–brain axis respond to |
The theme running through all of that is integrity. A well-fed gut lining with strong tight junctions is better at keeping what belongs in your gut inside your gut — which is the foundation of the anti-inflammatory and whole-body effects researchers keep linking butyrate to.
The honest caveat
We try not to oversell, so here's the fair version. Butyrate production from resistant starch varies from person to person, because everyone's microbiome starts in a different place (Teichmann & Cockburn, Frontiers in Microbiology, 2021). If you're missing some of the relay-team species, you'll respond differently than someone who has a full roster.
The good news is that the relay strengthens with use. Feeding your colon a steady supply of resistant starch tends to favour exactly the bacteria that build and sustain butyrate production. Consistency, again, beats intensity.
Where Mr. Regular fits
Mr. Regular +Prebiotic is built around three prebiotic fibres — organic psyllium husk, Orafti® inulin, and Solnul® resistant starch — and each feeds the microbiome a little differently. Solnul is the one doing the heavy lifting on the resistant-starch-to-butyrate pathway, at a clinically studied dose of 3.5 grams a day that's gentle enough to take daily without the bloating bigger doses can cause. (If your main goal is simply gentle, reliable regularity, Mr. Regular Original is built around organic psyllium husk — the gold-standard fibre for constipation.)
That's the whole idea: a simple, daily, prebiotic-first fibre that quietly keeps the butyrate factory in your colon well stocked.
The takeaway
You can't eat your way to more butyrate, but you can grow it. Resistant starch like Solnul® reaches your colon intact, feeds a relay team of bacteria, and the end product — butyrate — becomes the primary fuel for your gut lining, a guardian of your gut barrier, and a quiet contributor to lower inflammation throughout your body.
Feed the garden. The butyrate takes care of the rest.
References
- Parada Venegas D, et al. Short-chain fatty acids (SCFAs)-mediated gut epithelial and immune regulation and its relevance for inflammatory bowel diseases. Frontiers in Immunology. 2019. Read the study.
- Teichmann J, Cockburn DW. In vitro fermentation reveals changes in butyrate production dependent on resistant starch source and microbiome composition. Frontiers in Microbiology. 2021. Read the study.
- Bush JR, Baisley J, Harding SV, Alfa MJ. Consumption of Solnul™ resistant potato starch produces a prebiotic effect in a randomized, placebo-controlled clinical trial. Nutrients. 2023;15(7):1582. Read the study.
- Belenguer A, Duncan SH, Calder AG, et al. Two routes of metabolic cross-feeding between Bifidobacterium adolescentis and butyrate-producing anaerobes from the human gut. Applied and Environmental Microbiology. 2006;72(5):3593–3599. Read the study.
This article is for general education and isn't medical advice. If you have ongoing digestive symptoms or take medication, please speak with your doctor or pharmacist.