Our bodies need energy to grow and repair themselves, keep warm and do physical activity. Energy comes from food and drink, in particular from carbohydrate, protein, fat and alcohol. This energy is measured in kilojoules (kJ) or calories (kcal), with 1 kilocalorie equalling 4.2 kilojoules. In nutrition calorie and kilocalorie are sometimes used to mean the same thing.
Carbohydrates are the main providers of energy in our diet. Every body cell, including the brain, requires a constant supply of glucose as fuel, most of which is provided by the carbohydrates in food and drink.
Foods rich in fibre also contain powerful protective agents, such as antioxidants and phytochemicals. High fibre diets can also help in weight control and the management of diseases such as diabetes.
Protein is a source of energy but its main role in the body is growth and repair. It helps in the formation of muscles, hair, nails, skin and organs, such as the heart, kidneys and liver
Contrary to popular belief, fat is an essential nutrient with a host of important functions within the body. It is essential for supplying the body with omega 3 and omega 6 essential fatty acids, producing healthy cell membranes and maximising the absorption of fat-soluble vitamins and fat-soluble antioxidants (such as lycopene and beta-carotene). Fat is found in many foods and comes from both animal and vegetable sources.