Irritable Bowel Syndrome Message Boards | SF, solubility and transit time

Here is my take on what you have read.

Polycarbophil is derived from vegetable gums.

Gums are polysaccharides. They similar to sugars but composed of many sugar units making up large indigestible molecules. When placed in water they link too many water molecules increasing the viscosity (thickness) of the solution. They are indigestible in the stomach and small intestine but ferment (digested by bacterial) in the large bowel. I am not familiar with the fermentation processes for SF from different sources. I understand there can be different fermentation processes for different SFs.

SF does not swell in the sense of absorb water like IF may. And soluble in term soluble fibre does not mean "the SF dissolves in the water" like sugar dissolves in water. It means soluble in the sense that the molecules interacts with water to produce something called a colloidal dispersion. A similar thing happens when you use cornstarch to thicken a pudding.

Apparently, American Association of Cereal Chemists defines soluble fibre as "the edible parts of plants or similar carbohydrates resistant to digestion and absorption in the human small intestine with complete or partial fermentation in the large intestine". Therefore by definition a SF is at least partially fermentable in the large bowel. Using a variety of enzymatic and chemical processes companies are modifying SFs to make them less fermentable in the bowel. I doubt there are any SFs that are completely unfermentable.

Transit times is an interesting topic. Short chain fatty acids, one of the byproducts of fermentation in the large bowel of SF. IF and sugars such as fructose, are colonic stimulants.

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