We also know they need more than just fuel to run properly - they also need things like oil to lubricate the moving parts in the engine, and coolant in the radiator to stop the engine overheating.
Cars also sometimes need spare parts, anything from new tyres (when the old ones wear out) to new body panels (to replace ones that have been damaged in an accident).
But what has this got to do with nutrition? Well a car is a machine and so is your body - it is a very complicated, biological machine.
You consume food and drink in order to give yourself the energy you need to live and to move, just like putting fuel into a car.
But also like a car, your body needs more than just fuel to run properly - there are lots of different substances found in or food and drink and our bodies need many of these substances in order to keep them working properly; effectively we get our 'oil', our 'coolant', our 'spare parts' from what we eat and drink.
When we think about nutrition - these essential substances that our bodies need - we tend to break things down into six main categories (or nutrient groups):
- Water: Hopefully this one is obvious - we all need water to live, it makes up a large proportion of what we are actually made of, including being a major component of our blood (which helps transport all the other nutrients around our bodies).
- Carbohydrates: These provide a fuel source for your body.
Like any machine your body needs a source of energy and we can get some of this from the carbohydrate contained in our food; moving around requires energy, thinking uses energy (a surprising amount of it - our brains account for 20% of our total energy needs when we are at rest), indeed your cells are all using energy to just stay alive from moment to moment. - Fats: Fat is a bit of a dirty word nowadays, but fats are actually an essential part of our diet.
Like carbohydrates, fats provide fuel/energy for your body, but they also perform other important functions including forming part of the membrane that surrounds each of your body's cells (the skin of the cell if you like, so pretty essential), helping protect the nerve fibres in your brain, and helping you to absorb essential vitamins from your food (vitamins are discussed below). - Proteins: Your body can actually use protein for energy too, if there is not enough carbohydrate or fat around, but protein is also essential for building and repairing muscles, red blood cells, hair, and other tissues.
- Vitamins: We only consume vitamins in very small amounts compared to the other nutrient groups listed above, but they are nevertheless essential for good health.
There are a number of different types of vitamin and they help regulate many different processes in our bodies. - Minerals: Again we only need small quantities of these but they are essential for health.
The word mineral makes it sound like something you would get out of a mine or quarry! Actually that is no false impression - we are indeed talking about those sorts of minerals, things like calcium for your bones, iron that is essential for your blood, and sodium (a component of salt) that is necessary for your cells and nervous system to function normally.