Calories on nutrition information label

[MunkeyBoy]

What does the Kcal and KJ on the nutrition information on food labels in the Energy column mean? Which one is the calories? And why are they two different amounts? Please help

[nicola_red]

Kcal is calories.  KJ is kilojoules.  Apparently kcalories x 4.8 = kilojoules.

[bernardo]

There are about 4.2 calories in a Joule (or is it the other way round?).  Anyway, a calorie is the amount of heat needed to raise the temperature of 1 gramme of water by 1 degree Celsius.  A Calorie is the amount of heat needed to raise the temperature of 1 kilogramme of water by 1 degree Celsius.  There are 1000 calories in a Calorie, so a Calorie is often called a kilocalorie or a Kcal.

 

A Joule is the amount or work done by a force of 1 newton for 1 second (I think) (or something like that).  As far as physicists are concerned, "work", "heat" and "energy" are all the same thing really.

[Gef]

1 calorie = 4.18 joules. However, this is a very small amount of energy and so we normally use kilocalories or kilojoules. In food terms the kilocalorie is often called a Calorie (capital C). An active grown man needs about 2500 kcal or 10000 kJ per day.