All living things need food to survive. It gives us energy for everything that we do. It also gives the body what it needs to repair muscles, organs and skin. Food helps us fight off dangerous diseases.
It is important to eat a wide range of food in order to stay healthy. Nutrition is the science that deals with food and how the body uses it.
How the body uses food
Food has nutrients in it— substances that give our body many important things that we need. They provide us with energy and also help control the way our body grows.
Before nutrients can go to work food must be broken down so that they can pass into our body. This is called digestion. It starts when we chew the food that we eat. When we swallow it it travels on to the stomach where it is mixed together with water and other fluids. Then the food is passed on to the intestine. Nutrients escape through the walls of the intestine into our blood. From there they are carried to all parts of the body.
Most food leaves waste that the body cannot use. Some of it goes to the kidneys and turns into urine. The liver also filters out waste. What is left over passes through the large intestine and leaves our body.
There are six main groups of nutrients: proteins, carbohydrates, fats, vitamins, minerals and water. The energy that food gives us is measured in kilocalories, or one thousand calories. A calorie is the energy that is needed to raise the temperature of water by one degree Celsius.
Although water does not give us energy it is the most important nutrient. We may be able to live on without the others for weeks, but we cannot go on without water for more than a few days.
Water has many functions in our body. It helps break down food. It also cools the body down when it becomes too hot. The body carries away waste products in a watery solution.
Our body needs about 2 –3 litres of water a day. We get it from the water and liquids we drink but also from fruits, vegetables and other food.
Carbohydrates are the main source of energy for our body. Sugars and starches have carbohydrates in them.
Sugar is a simple carbohydrate. It gives us energy very quickly. This form of energy can be found in dairy products, honey, syrup, jams and jelly.
Starches must be broken down into sugars before our body can use them. They are found in beans, bread , potatoes, cereals, corn, pasta, peas and potatoes. They provide our body with a constant supply of energy.
Our body needs fat in small amounts. Fats are made up of carbon, oxygen and hydrogen. They store vitamins and produce fatty acids. We need these acids to produce cell membranes.
Fats can come from animals or plants. They are in meat and dairy products, like butter and cheese. Other types of fats are in vegetable oils, nuts or seeds.
Too many saturated fats produce a high level of cholesterol, a waxy material made by the body. It starts building up in the walls of blood vessels and may block blood as it flows through our body.
Proteins are among the most important building blocks of our body. Muscles, skin and hair , for example, are made up of proteins.
Proteins are complex molecules made up of amino acids. The body can produce some of them itself, but we must get the others from food. Proteins are in cheese, eggs, fish, meat, milk, as well as in nuts, peas and beans.
Minerals are needed for growth. They are inorganic, not made up of living things. Our body needs different amounts of various minerals. Calcium and magnesium, for example, are important for bones and teeth. We also need small amounts of iron. It is a component of haemoglobin, which carries oxygen to red blood cells. Fluorine or zinc are other minerals we need in very small amounts. They are called trace elements.
Our body needs a variety of vitamins to stay healthy. Each of them does a different job. Vitamin A, for example, helps skin and hair grow. Vitamin C is needed to fight off infections. Vitamin D helps the growth of bones and teeth
The right diet
The key to staying healthy is eating the right food. Nutritionists suggest eating according to the food guide pyramid. It has five sections. You should eat a lot of the bottom parts, but only a little of the upper parts.
The Food Pyramid
- Be careful of your weight. Obesity can lead to health problems.
- Exercise every day. It helps the body burn calories and the fat you don’t need.
- Eat a lot of grain products
- Be careful not to eat food that has too much saturated fat and cholesterol
- Do not eat too much sugar. High-sugar foods and drinks have a lot of calories but not many nutrients.
- Don’t put too much salt on your food. This may lead to high blood pressure.
- Include fiber in your diet. It helps food move along in your body.
- Beware of alcoholic drinks. They have a lot of calories but no nutrients.
- Store and cook foods properly so that they do not lose their nutritional value.
Nutrition and diseases
All over the world people suffer from illnesses that are caused by eating the wrong food or not having enough to eat.
In developing countries deficiency diseases arisewhen people do not get the right nutrients. Kwashiorkor is a disease that occurs if your body doesn’t get enough proteins. Marasmus occurs in young children who don’t get enough calories every day. They become weak, underweight and often die.
Diseases often occur if you suffer from a lack of vitamins. Not enough vitamin D, for example, may lead to bone illnesses.
In industrialized countries people often suffer from eating too much. Too much fat and cholesterol in your body can lead to heart diseases, obesity and cancer. High cholesterol levels may make your arteries narrow . The result may be high blood pressure , a heart attack or a stroke.
The lack of certain minerals may also lead to illnesses. Not enough iron in your food reduces the blood’s ability to make red blood cells, which are needed to transport oxygen through our body.