ellen wickberg wrote:
> in article , Andy Petro at
> wrote on 11/8/04 1:45 PM:
>
>>Anyone know how the number of calories in the different kinds of food are
>>measured . Is it chemical,heat or other.
>>No one seems to be able to tell me.
>>
> used to be burned in a bomb calorimeter.
Sorta. They measure actual caloric content of fats and proteins but
estimate carb counts. It called "by exception" and means that anything
not a fat or protein is automatically designated a carb whether we can
digest it or not. So the calorimeter measures total energy, some of
much of which isn't available to us. Cellulose is technically a carb,
but we don't digest it. Likewise pectin. In full-scale descriptions,
they'll generally be listed as fiber under carbs, but the calories
they contain will be included in the total. There are some fibers that
we digest partially, and that clouds the issue a bit further. Sugar
alcohols are like that. They're fewer calories than other sweeteners,
but they still carry some. Just to make that one more complex,
different people digest them to varying degrees. Caloric info on food
labels are approximations.
BTW, alcohol is another macro nutrient at 7 cals/gm that isn't often
listed on labels.
I think the USDA nutrient database explains all that, IIRC.
Pastorio