fiber - blood sugar?

I believe they are two separate functions.

Fiber helps moderate carbohydrate metabolism, slowing the blood sugar rise, by slowing digestion.

Fiber helps controls bowel movements in the presence of diarrhea by absorbing excess water in the bowel. This thickens the stool and makes it easier to retain.

Jan

Ah.  I knew it thickened stool by absorbing water but wasn't aware that it slowed digestion as well.

In this case "slowing digestion" has nothing to do with BM frequency or consistency. The effect of soluble fiber on BMs is purely mechanical.

Yes, it slows digestion simply because fiber takes longer to process. But that does not necessarily translate to a slower transit time. Transit time and digestion are two different things. 

Jan

What is the distinction between transit time and digestion?

Transit time is the time it takes from putting food into your mouth until its residue gets to the finish line. Digestion is the mostly chemical processes of turning food into molecules that can be absorbed through the gut into the blood.

Thank you Scott. Well stated.

So here's the point:

You can have a transit time of an hour (time from eating to bowel movement), yet have adequate digestion of nutrients. Digestion and absorption of nutrients depends largely upon the health and length of your small intestine, proper pH levels, and presence of enzymes and hormones. 

Slower digestion helps mediate spikes in blood sugar (important for diabetics). 

Slower transit time might allow for better digestion if your ability to digest is impaired (such as with Crohn's disease, celiac disease, or short small bowel length). 

To further confuse things, thickening your stool does not necessarily alter transit time to any siginicant degree, but it might make it appear so. Stool consistency may be purely a functional issue. Like adding cornstarch to make pudding, thickening stool just makes it easier to hold in your pouch, but does not slow the gut.

Jan