Food for our bodies
Just as plants need a source of energy to live and grow, so too do our bodies. Every activity from breathing to running requires energy. We get our energy from the nutrients in food. The main sources of energy are carbohydrates (starches, sugars), fats and protein. The body can be compared to an engine which converts the energy in food into the energy we need to live. All energy in food is measured using a unit called a kilojoule (kJ) or kilocalorie (kcal).
1g of fat provides
1g carbohydrate provides
1g of protein provides
You need energy for all the activities you do. The more active you are, the more energy from food you require. Typically 12 year-old boys require about 9000kJ each day, whereas 12 year-old girls require about 8000 kJ per day.
It is important that you have the right amount of energy to meet your needs. If you do not have enough, then you will not grow at the correct rate and you will lose weight. However, if you take in more energy that you use up, over a period of time you will put on weight. This is because excess energy from food is converted into body fat.
Apart from providing energy for all activities, food gives us the building blocks for growth, and the maintenance and repair of our bodies. In addition to the major nutrients - carbohydrates, fats and protein - we also require water, vitamins and minerals, which are vital for many of the body’s processes. We also need dietary fibre for the smooth passage of food through the body.
Sugars and starches are forms of carbohydrate. It is recommended that about half our energy should come from carbohydrates. The majority of this should be from starchy foods like cereals, rice, potatoes, pasta or bread. During digestion (the process by which we break down food substances so that they can be absorbed and used by the body) carbohydrates are broken down into individual sugars.
The balanced diet
It is important that we get the right amount of nutrients. Different foods contain different nutrients. For example, bread, rice, pasta, potatoes and cereals contain mainly carbohydrate in the form of starch. Fruit, fruit juices, honey and table sugar contain mainly carbohydrate in the form of sugar. Butter, margarine, oils, meat and dairy products are sources of fat, whereas protein is found in a wide range of foods from meat, fish, cheese and eggs through to cereals and vegetables such as peas, beans and lentils.
Most foods contain more than one nutrient. For example, milk provides fat, protein and sugar (lactose) and is a good source of the mineral calcium and the B vitamin riboflavin. Potatoes provide starch, dietary fibre and can be an important source of vitamin C. A sponge cake provides starch, sugars, fat, protein and a variety of vitamins and minerals. As all foods contain a different mix of nutrients, the key to a balanced diet is to vary the food you eat as often as possible.
For further information on a healthy, balanced diet visit the British Nutrition Foundation website.
Years ago, tooth decay was very common and children were likely to have many decayed or filled teeth. Today most children have one or two fillings, so dental health is improving.
The decay process begins when bacteria, which live in our mouths, use the sugars and starches in our food to produce acid. Starches can be broken down slowly in the mouth to sugars. The mixture of food and bacteria which forms on teeth is called plaque. The bacteria in plaque break down sugars to form acid which then attacks the enamel coating of the teeth. Given time between attacks, the enamel can rebuild itself, but if the acid attacks are too frequent, cavities may form. The more times you eat foods containing sugars or processed starch during the day the less time there is for your teeth to recover.
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