The carbohydrate in fiber cannot be digested by humans (some animals can), therefore the carbs and calories don't count (if you're human - if you were a cow you'd have to count them). Food manufacturers in the USA (this isn't true in all countries) are allowed to subtract fiber calories (because they don't count), but they're not obligated to - and whether they did or didn't usually isn't listed on the label.
To me, it seems that if humans can't digest fiber, the fiber calories should never show up on a label for foods meant for human consumption. But that's not the law. The law says to these food manufacturers "count them, or don't count them - your choice).
Since I don't know whether or not the food manufacturer has subtracted fiber calories, I tend to take the calorie count at face value (assume it's accurate), but if you're counting carbs and not calories, you definitely can subtract fiber carbs, because those carbs aren't digestible (they leave your body intact - TMI, but it's one of the reasons why some animals eat other animals' poo, or eat stuff out of other animals' poo, because of the undigested stuff in it that still has calories).
Sugar alcohols also aren't fully digested, but there's conflicting evidence over how much is digested. Some argue that for most people it's none. Others say that some people seem to be able to digest about half. Because of the conflicting evidence, some people choose to substract some, half, or none of the carbs from these sugar alcohols. Others say that if they cause diarrhea it's "proof" that you're one of the people who can't digest sugar alcohols. I don't know if there's any scientific link between laxative effect and whether or not you can digest the sugar alcohol carbs or not.
I know that may seem to make the issue cloudier, but the simple answer is YES you can subtract fiber carbs - all of them.
and MAYBE you can subtract sugar alcohol carbs (or some of them).
Last edited by kaplods; 05-13-2011 at 08:22 PM.