Calculating energy value of food from nutrition information
Energy value refers to the amount of energy supplied by a certain amount (e.g. per gram, per 100 grams) of food. Food provides the energy needed for essential functions in the body. Three key substances in food that provide energy are carbohydrates, proteins, and fats and oils. Their energy content is shown in the table below. Understanding food energy helps in assessing nutritional value and making informed choices.
| Food | Energy (kJ g-1) |
|---|---|
| Fats and Oils | 37 |
| Protein | 17 |
| Carbohydrates | 16 |
Click on the hotspots to find out the different types of food energy information provided in food labels.
Worked example
Ethan had one serve of Weet-Bix for his breakfast. Calculate the amount of energy contained in one serve of Weet-Bix according to the information from the following nutrition table. Use the energy content for different food molecules as shown in the image and table above.
Solution
According to the table above, each serve contains 3.8 g of protein, 0.4 g of fat, and 20.4 g of carbohydrates.
- Energy from 3.8g of protein can be found using: \(\text{mass of protein}\times\text{energy content of protein}=3.8\times1.7=64.6kJ\)
Similarly:
- Energy from 0.4 g fat = \(0.4\times37=14.8kJ\)
- Energy from 20.4 g of carbohydrates = \(20.4\times16=326.4\)
\(\text{Total energy}=64.6+14.8+326.4=4\times10^2kJ\)
