Food energy is chemical energy that animals derive from food to sustain their metabolism and muscular activity.
The energy contents of a food or meal can be approximated by adding the energy contents of its components, though the entire amount of calories calculated may not be absorbed during digestion.
History and methods of measurement
Direct calorimetry of combustion
The first determinations of the energy content of food were made by burning a dried sample in a bomb calorimeter and measuring the temperature change in the water surrounding the apparatus, a method known as direct calorimetry.
Dietary sources of energy
The typical human diet consists chiefly of carbohydrates, fats, proteins, water, ethanol, and indigestible components such as bones, seeds, and fibre (mostly cellulose). Carbohydrates, fats, and proteins typically comprise ninety percent of the dry weight of food. Ruminants can extract food energy from the respiration of cellulose because of bacteria in their rumens that decompose it into digestible carbohydrates.
Other minor components of the human diet that contribute to its energy content are organic acids such as citric and tartaric, and polyols such as glycerol, xylitol, inositol, and sorbitol.
Some nutrients have regulatory roles affected by cell signaling, in addition to providing energy for the body.
According to the Food and Agriculture Organization of the United Nations, the average minimum energy requirement per person per day is about . Notwithstanding, nutrition labels on Australian food products typically recommend the average daily energy intake of .
The minimum food energy intake is also higher in cold environments. Increased mental activity has been linked with moderately increased brain energy consumption.
External links
- Is a calorie a calorie?
- DRI Calculator for Healthcare Professionals