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The four ‘tastes’

There are four basic tastes: sourness, saltiness, sweetness and bitterness. We taste with special sense cells which are mainly on the surface of our tongue which are grouped together to form taste buds. Each type of taste bud is only activated when arriving food molecules fit the shape of receptors on its surface, rather like a key fitting into a lock. The taste bud then sends messages to the brain where they are decoded and registered as a ‘taste’.

Sweetness in nature

Sweetness can often be an indication of food which is safe to eat, compared with poisonous fruits and plants which tend to be bitter (eg mistletoe berries). However, it is best not to eat unfamiliar fruits or berries just in case they are poisonous.

Plants use nectar and fruit, which are rich in sugars, to attract insects, birds and mammals which in turn help plants to reproduce. For example, when bees pass from flower to flower drinking nectar they also pick up pollen and transport it to other plants which may result in fertilization and seed formation. Birds eat fruit containing seeds. These pass through their stomachs almost intact and are scattered around the countryside, eventually growing into new plants.

Sugars are present in the diet of many animals. For example, the sugars in berries provides energy for woodland animals and nectar contains a solution of sugars, which a bee uses to fuel its flying (bees’ wings flap at 18,000 beats per minute!). The bee also uses the nectar to produce a food to fuel us – honey!

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).

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.

Carbohydrates

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.

Tooth decay

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.

The guide to a permanent smile

It is important to take steps to look after your teeth properly so that they last a lifetime.

Brushing teeth helps to remove bacterial plaque from the surface of the teeth. It is best to do this at least twice a day. Chewing a disclosing tablet can show the areas which still have plaque on them.

Use a small toothbrush with short bristles. Make sure that you reach all the surfaces of your teeth, including those at the back. Don’t forget to clean along the edges of the gums, and in between individual teeth.

Use a toothpaste which contains fluoride (in some places fluoride is added to drinking water). The fluoride helps to protect the teeth from the action of acids produced by the mouth bacteria by making the enamel stronger.

Eat and drink sensibly. It is not simply what we eat, but how often that matters. Try not to eat sugary foods too often.

Visit the dentist at regular intervals for a check up (about every six months).

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