I am diabetic. I have a question about nutritional labels. I am most concerned with carbs that affect blood glucose.
Many times I will see a label with 9g total carbs, 3g fiber, and 2g sugar. What are the other 4g of carbs and are how do they affect blood sugar? Shouldn’t sugar + fiber = total carbs?
Sometimes there are sugar alcohols listed as well, but often their inclusion does not round out the total carb count.
First of all, fibre is not counted as carbohydrate. Fibre is, well, indigestible stuff. Technically it is carbohydrate I suppose, but you don’t digest it so it is not dietary carbs.
Basically, carbohydrate is sugar and starch. Potatoes and bread, for example, contain a load of carbohydrate but not much sugar. It’s mostly starch.
Over here in the UK, at least, labels will typically say something like:
Per 100g:
Carbohydrate 26g
(of which sugars 9g)
Which tells you that there’s 15g of starch (assuming no funky stuff like alcohol etc).
In your example:
you shouldn’t take the 3g of fibre away from the 9g of carbs - it is separate. So you have 2g of sugar and 7g of starch.
I’m not qualified to answer the second part of your question (about diabetes), although my wife is diabetic, so she would know more. As I understand it, though, complex carbs (starch) do get converted into blood sugar but less quickly than simple carbs (sugar), particularly when combined with fibre.
Actually, it looks like I might be wrong about total carbs not including fibre, at least on US “Nutrition Facts” panels. They do seem to include the fibre, which seems an odd way of doing it. As far as I know, UK labels list it separately, but I am finding it very hard to confirm this.
But anyway, the “missing” carbs you mention are starch.
I believe other ingredients that may affect the count like glycerin and dextrose? I know a packet of Splenda has a carb from the dextrose and Atkins bars consider glycerin a low impact carb so they subtract for the net.