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Food Energy
Food energy
is the amount of energy in food that is available through digestion.Food
energy is typically measured in units of calories, although the
International System of Units unit kilojoules (1000 joules) are
becoming more common.
Some types
of food hold more food energy than others: fats and sugars have
particularly high food energy levels.Note that the "calorie"
used by dieticians for food is sometimes called a kilocalorie;
it is equal to 4.1868 kilojoules.
Food Energy Measurement
In the early
twentieth century, the United States Department of Agriculture
(USDA) developed a process for measuring food energy that remains
in use today.
The food
being measured is completely burned in a calorimeter so that the
heat free through combustion can be accurately measured. This
amount is used to determine the gross power value of the particular
food. An adjustment is then made based on how the human body actually
digests the food.
For example,
clean sugar releases about 3.95 Calories per gram of gross energy
but the digestibility coefficient of sugar is about 98% in humans,
so the food energy of sugar is 3.87 Calories per gram of sugar.
Energy Content
Protein contains about 4 (nutritional)
calories per gram.
Carbohydrates contains about
4 calories per gram.
Fat contains about 9 calories
per gram.
Alcohol contains about 7 calories
per gram.
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