Vitamins, minerals and water supply little or no energy. It would take a long time to work out the amount of nutrients and energy provided by foods, so food tables have been compiled to provide us with this information. The nutrients and kilocalories in a food may be shown by unit (e.g. in one egg) or by weight (e.g. per 100 g).
• 1 gram of protein produces 4 kcal (17 kJ) • 1 gram of lipids produces 9 kcal (37 kJ) • 1 gram of carbohydrates produces 4 kcal (17 kJ)
Food packaging provides nutritional information about a product. This simplifies the planning of meals and caters for all ages and dietary needs. It also helps those with special requirements and allergies to avoid certain food additives.
Functions of energy • To keep vital organs such as the heart and lungs working. • For muscle movement and daily activities (running, dressing, writing). • For normal nerve function. • For cell activity and growth of cells in children, teenagers and pregnant women. • To maintain correct body temperature (37°C). • Extra energy is needed in colder climates.
Factors that influence energy requirements Activity levels – active people use more energy than less active people. Size – smaller people use less energy than larger people. Gender – females require less energy than males as they have a lower muscle ratio. Age – a child or adolescent needs more energy for their size than an adult. Pregnancy – extra energy is needed for growth during pregnancy and for breastfeeding. Climate – in cold climates more energy is needed to keep warm.
Discovery Learning Try and come up with a mnemonic to remember the factors that influence energy requirements. Share your ideas with the rest of your class.
