So I've been researching this for a while and still can't figure out the difference between Soluble and Insoluble fiber.

From what I've read, insoluble fiber will make up bulk and will speed up the process of food passing through bowels.
Soluble fiber will form a coating gel in upper intestine and will slow the passing of food a bit, and all of it will be completely destroyed by the time it reaches the lower intestine.

Yet the majority of users on this forum seem to prefer soluble fiber for soft stools. I don't understand how that can actually be, based on what I've described above.

Thoughts?

Hi Powderblue,
It's a complicated subject and I don't fully understand it myself, but I think the quick answer to your question is that soluble fibre contributes to the osmotic force of your intestinal contents. ie, soluble fibre consists of sugars (why it dissolves), and is able to draw water into the intestine. More water = softer stools.

Soluble fibre is sugars that you cannot digest or absorb yourself. You can't digest it, but your gut bacteria can. This anaerobic bacterial digestion (fermentation) often releases gases, which is why some foods are gassy - there are indigestible sugars in beans for example.

How much of the soluble fibre is left by the end of the food's passage through the gut, will depend on your gut bacteria, what they can digest, etc. This might be one reason why some foods work really well as stool softeners for some people and not for others - everybody has a different gut flora.

I would guess that insoluble fibre helps stools by speeding food through the gut. The longer stool stays in the colon, the drier it gets, so anything that speeds it through will help. You probably need the insoluble fibre to off-set the slowing effect of soluble.

Insoluble fibre is cellulose etc from plant cell walls. It doesn't dissolve in water.

I hope this helps?