"Soluble" and "insoluble" fibre get talked about constantly, but rarely explained clearly. If you're dealing with constipation, knowing the difference helps you choose the right product instead of guessing.
What is insoluble fibre?
Insoluble fibre doesn't dissolve in water. It adds bulk and helps move material through the digestive tract — think wheat bran, whole grains, and the skins of many fruits and vegetables. It can help with regularity, but for sensitive guts it's sometimes harsh and can cause discomfort.
What is soluble fibre?
Soluble fibre dissolves in water and forms a gel. This gel softens stool, supports steady digestion, and feeds beneficial gut bacteria. Sources include oats, legumes, and — importantly — psyllium husk.
So which one helps constipation?
Here's the nuance most articles miss. You'll often read "use insoluble fibre for constipation." But the single most clinically recommended fibre for constipation is actually psyllium, a soluble fibre — because it's unusual. Psyllium is both gel-forming and bulk-forming: it holds water to soften stool and adds the bulk that gets things moving, while staying gentle. That combination is why gastroenterologists reach for it. Here's a deeper look at how psyllium works.
Why a blend can be even better
Beyond easing constipation today, the right fibres support your gut long term. Prebiotic fibres like inulin and resistant starch feed the beneficial bacteria in your microbiome, which underpins healthy, comfortable digestion over time.
That's the thinking behind our products. Mr. Regular Original pairs organic psyllium with prebiotic inulin, while Mr. Regular +Prebiotic adds Solnul® resistant starch for deeper microbiome support. You can see the full breakdown on our science page.
Frequently asked questions
Is psyllium soluble or insoluble?
Psyllium is primarily a soluble, gel-forming fibre — but it also adds bulk, which is why it's so effective for constipation.
Do I need both types of fibre?
A varied diet naturally provides both, and that's ideal for overall health. For constipation specifically, a quality psyllium-based supplement is the most reliable single choice.
Can too much fibre cause constipation?
Too much fibre without enough water can. Increase fibre gradually and drink plenty of fluids.
This article is for general education and isn't medical advice. For persistent digestive issues, please speak with a healthcare professional.