Dear Tom and Kitty:

I am having a little problem understanding parts of the food labels,
which I will need to talk about in next week's lecture. I.e. when
reading the label from a bag of sugar it states "carbohydrates"
and "sugars", but it only contains "sugar". Where is the
carbohydrate coming from - since the carbs turn into "sugar"?

Thanks

-Niko

[Carbohydrate is a very large chemical group including:
1) Sugars - which are mono and disaccharides
2) Starches - which are digestible polysaccharides
3) Fibers - which are indigestible oligio- and polysaccharides

However, the nutritional definition of fiber also includes lignans which
are not carbohydrates, chemically. In addition, there are at least two
major classifications of fiber: soluble (which slows digestion and
decreases glycemic index) and insoluble (the kind which is good for the
colon). Both types of fiber are digested somewhat by the bactera in the lower
intestine and colon and do produce some small amount of calorie intake for the
body through that process (absorption of some of the metabolites). However,
these calories are not counted in the food labeling as far as I know.

The FDA labeling requirements are to list:

a) total carbohydrate
b) sugar
c) fiber

The difference a - (b + c) is then the amount of starch in the product.

However, the FDA also defines carbohydrate incorrectly as everything
which is not protein, fat, water or mineral, so the carbohydrate content
of a product is sometimes a little higher than it chemically really is.
You will see this if you compare the USDA analysis for a product with
the label analysis.

A diabetic should be concerned with both the starch and the sugar, and also with
their types. If the starch is fast digesting (eg. potatoes) then it will in
effect act like a sugar. If the sugar is glucose then it has a higher glycemic
index than sucrose (a disaccharide) which is only half glucose, the other half
being fructose - a low glycemic index sugar (ie. it converts only slowly to
glucose). A major short-sightedness occured in the past (and is still with us)
when manufacturers began to use high fructose sweetners mainly because of
diabetic users, since in the long run fructose is even less healthy than glucose
because it has a much higher protein glycation rate.

Finally, a diabetic does not need to worry about the fiber (wrt to blood glucose
that is). In fact, if the amount of soluble fiber is high then that is
beneficial, since it will slow the rate of digestion and decrease the glycemic
index (just as will protein and fat). --Paul]