What Do We Count Counting
Carbohydrates?
by Tanya Zilberter, PhD
What Is
Total Carbohydrate? Active versus non-active, available versus
unavailable, etc.
Also on the topic:
Glycemic Index Meal Plan
Glycemic
Index
The
Glycemic Index: Flogging a Dead Horse?
Carbohydrates and Other Macronutrients: How Much?
CARBOHYDRATES: chemically speaking, they include such
diverse groups as aldehydes, ketones, alcohols, acids, their simple
derivatives and their polymers_
Carbohydrates may be divided into three principal groups, namely
sugars, oligosaccharides and polysaccharides. Sugars --> Monosaccharides (Glucose, galactose,
fructose) - Disaccharides (Sucrose, lactose, trehalose) - sugar
alcohols (Sorbitol,
mannitol) Oligosaccharides --> Malto-oligosaccharides
(Maltodextrins) - Other oligosaccharides (Raffinose, stachyose,
fructo-oligosaccharides) Polysaccharides --> Starch (Amylose, amylopectin,
modified starches) - Non-starch polysaccharides (Cellulose,
hemicellulose, pectins, hydrocolloids)
What Is Total Carbohydrate?
Calculating carbohydrates by "difference"
The protein, fat, ash and water grams of a food are measured,
subtracted from the total weight of the food and the remainder, or
"difference", is agreed upon to be carbohydrate.
However, the "by difference" grams include plenty of
non-carbohydrate components such as lignin, organic acids, tannins,
waxes, etc.
Finally, a single global figure for carbohydrates in food doesn't
tell most interesting things about the food's nutritional value because
it can't identify the of carbohydrate types and doesn't describe
physiological properties of those carbohydrates.
Sugar or Sugars?
The chemical term "sugars" describes the mono and disaccharides.
"Sugar" is used to identify refined sugar and added sugar.
Healthy and unhealthy sugars
The terms "extrinsic" and "intrinsic" sugars were developed in UK
to help the consumer choose between what were considered to
be healthy sugars and those which were not. Intrinsic sugars were
defined as sugars naturally occurring within the plant cell, while
extrinsic sugars were those which were usually added to foods. However,
nutritionists don't plan to measure these sugars separately in the diet
or to incorporate them into food tables.
Complex carbohydrates
The term was introduced in order to distinguish sugars
from fruit, vegetables and whole grains. The term is used to describe
either
starch, or the combination of all polysaccharides as well as to
encourage consumption of what were considered to be healthy foods such
as whole grain cereals, etc. However, it is now realized that starches,
as complex carbohydrates, are not created equal: some are being rapidly
absorbed and having high glycemic index and some being
resistant to digestion (low glycemic index). Available and
unavailable carbohydrate
Not all carbohydrates could be utilized or "metabolized". Available
carbohydrates are defined as "starch and soluble sugars" and
unavailable as "hemicellulose and fiber (cellulose)".
However, it can be misleading to talk of carbohydrate as
"unavailable" because some carbohydrates seen as "indigestible " are in
fact able to provide the body with energy through fermentation in one
part of the intestinal tract or another.
A more appropriate substitute for the terms "available" and
"unavailable" today would be to describe carbohydrates either as glycemic
(i.e. providing carbohydrate for metabolism) or non glycemic or
those that do not provide carbs for metabolism.
Source: FAO/WHO expert consultation on carbohydrates in human
nutrition
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