How Dietitians Calculate Calories In Food

Over the last 100 years, health professionals have discovered the importance of proper nutrition when it comes to health and disease maintenance. Much effort has gone into educating the public about the nutritional values of foods and how to eat for health. The duty of determining the nutritional value of foods has been a responsibility of the USDA and the FDA since their inceptions.

Method of Measuring Calories

The method to determine the amount of energy, in the form of heat, that a particular food product contains is called direct calorimetry. A direct calorimeter is a sealed box with instrumentation that can measure the heat produced when a food product is completely burned. Direct calorimetry is measured in kilo-joules, which is a very small and exact unit of measure. A kilo-joule is equivalent to 239 calories.

The Food Label

According to Hargove in August 2006 issue of the "Journal of Nutrition", when we read food labels, the calories are listed in Kilocalories or Calories with the "C" capitalized, which is equivalent to 1000 small "c" calories. So if a food produced 3kJ during direct calorimetry, then that would equate to .717 Calories (Kilocalories) -- 3kJ x 239calories/1kJ = 717 calories; 717calories x 1kcal/1000calories = .717 Kilocalories.

USDA Food Database

The USDA has been issuing dietary recommendations for over 100 years. Their research findings are continually being updated and placed into a database, accessible to anyone. Part of a dietitian's education is learning the caloric values for the basic foods, knowing where to locate the information and determining whole food product caloric values based on this collected data. There are other databases available such as Nutribase 9 and ESHA's software called Food Processor. These databases have calculated many foods on their own; however, they also utilize the USDA database as a portion of their database.