The calorie is a unit of energy. For historical reasons, two main definitions of “calorie” are in calories per gram of fat carb protein and alcohol use.
In nutrition and food science, the term calorie and the symbol cal almost always refers to the large unit. This unit was used by U. Joseph Howard Raymond, in his classic 1894 textbook A Manual of Human Physiology. In 1879, Marcellin Berthelot distinguished between gram-calorie and kilogram-calorie, and proposed using “Calorie”, with capital “C”, for the large unit. Already in 1928 there were serious complaints about the possible confusion arising from the two main definitions of the calorie and whether the notion of using the capital letter to distinguish them was sound.
