Nutrient

A nutrient is any element or compound that is necessary for or contributes to an organism's metabolism, growth, or other functioning. Nutrients can be divided into many categories, including, but not limited to:

• Carbohydrates: compounds based on sugars that mostly contribute energy
• Proteins: nitrogenous organic compounds, including amino acids, that provide the building blocks (amino acids) for enzymes and other proteins within the body
• Fats: including fatty acids (a fat is an assemblage of three fatty acids linked to a central glycerine molecule)
• Minerals: generally trace elements, pure elements or ions such as copper and iron
• Vitamins: certain compounds essential to the body's functioning

The energy content of fat is 9 kcal/g. of proteins and carbohydrates 4 kcal/g, and of ethanol (alcohol) 7 kcal/g.