In terms of human nutrition, there are a number of essential and conditionally essential nutrients. An essential nutrient is a nutrient that the body can’t produce in adequate amounts, so we must get it from our diet. A conditionally essential nutrient means normally the body can produce the nutrient in the amounts we need, but under certain conditions, such as in heart disease, the body can’t.
These nutrients can be divided into macronutrients (carbohydrate, protein and fat) and micronutrients (vitamins and minerals).
What are calories?
Regardless of which specific elements are consumed, the primary requirement of food and drink is energy. The metric units for measuring energy are kilojoules (kJ), but calories are the more commonly referred-to unit when talking about food energy. Although the word ‘calories’ is often used, strictly speaking, kilocalories is the correct term and the abbreviation is kcal.