A fibre with strong physical behaviour
Psyllium husk contains mucilage that swells in water and forms a viscous gel. That makes it different from fibres that mainly add dry bulk, dissolve without much body, or ferment quickly before creating a strong gel structure.
This physical behaviour is why psyllium appears in discussions about stool form, fullness, and bile acid movement. It is also why it can be difficult in manufacturing. The same hydration and viscosity that make psyllium valuable can cause clumping, grit, rapid thickening, or dosing problems if the system is not designed well. Psyllium is not just a fibre claim. It is a material with behaviour that must be managed.