Science Notes PDF

# Classification of Food No one can live without food. Proper food provides us energy for various body activities, protects us from diseases and regulates our body functions. There is no single, perfect food that can supply the requirements for proper nutrition all by itself. Foods can be classifie...

# Classification of Food No one can live without food. Proper food provides us energy for various body activities, protects us from diseases and regulates our body functions. There is no single, perfect food that can supply the requirements for proper nutrition all by itself. Foods can be classified according to their actions in the body, such as: - energy-giving foods (carbohydrates and fats) - body-building foods (proteins) - protective foods (minerals and vitamins) ## Body-building foods - milk, pulses, eggs, meat, fish, etc. ## Protective foods - fruits, green leafy vegetables, other vegetables, etc. Some food items included in three groups based on their action on the body # Are We Eating Right? Our meals have some components that are needed by our body. These components are called nutrients. Nutrients are the chemical substances present in food. They provide the energy and raw materials for growth, repair of tissues, reproduction and protection from diseases. The major nutrients in our food are named as carbohydrates, proteins, fats, vitamins and minerals. In addition to these, food contains dietary fibres and water, which are also needed by our body. However, all food items do not contain all these nutrients. Using some simple methods, we can test whether cooked food or a raw ingredient contains one or more of these nutrients. We can do these tests and record all our observations in a table. For carrying out these tests, you will need solutions of iodine, copper sulphate and caustic soda. You will also need a few test tubes and a dropper. Try these tests on cooked food items as well as raw ingredients. Some food items are given in the table on the previous page. You can conduct the tests either with those or any other available food items. Do these tests carefully and do not try to eat or taste any chemicals. If the required solutions are not available in readymade forms, they can be prepared in the laboratory itself. Do you know there are many types of carbohydrates? The main carbohydrates found in our food are in the form of starch and sugar. Fats, proteins and starch may be present in all the food items that you tested in the activity. You may have noticed while recording your observations that most food items usually have more than one nutrient. However, in a given raw ingredient, one particular nutrient may be present in much larger quantity than others. For example, rice has more carbohydrates than other nutrients. Thus, we say that rice is a 'carbohydrate-rich' source of food. Thus, foods can also be classified according to their nutrient-contents, such as, carbohydrates, proteins, fats, minerals and vitamins. # Activity 2 | Nutrients | | ----- | | Carbohydrates | | Fats | | Vitamins | | Proteins | | Minerals | # Role of Nutrients in our Body ## Carbohydrates and Fats (Energy-Giving foods) Fats and carbohydrates are also called 'energy-giving foods' as they are burnt by our body to release energy, which we need for our various activities. A physically active person like a construction worker, a sportsperson or a young child requires a lot of energy. Carbohydrates mainly provide energy to our bodies. Fats also give us energy. In fact, fats give us much more energy as compared to the same amount of carbohydrates. While carbohydrates give us instant energy, fats tend to remain stored under our skin for a longer time and are used up by our body only if we have no more carbohydrates left to be burnt. They are more like energy banks. Secondly, fats are difficult to digest while carbohydrates get digested very quickly. Excess of fats may cause a great deal of harm to the body. They are stored as fat tissues under the skin and cause obesity as well as heart problems. ## Proteins (Body-Building Foods) Proteins are needed for the growth and repair of our body. Foods containing proteins are often called 'body-building foods'. A growing child like you, a pregnant woman and a person recovering from a disease would require proteins in large quantities. ## Vitamins and Minerals (Protective Foods) Vitamins help in protecting our body against diseases, and keep our eyes, bones, teeth and gums healthy. They are of different kinds and known by different names, such as Vitamin A, Vitamin B, Vitamin C, Vitamin D, Vitamin E and K. Our body needs all types of vitamins in small quantities. - Vitamin A keeps our skin and eyes healthy. - There is a group of vitamins called Vitamin B-complex. They are important for good digestion, memory and so on. - Vitamin D helps our body to use calcium for healthy bones and teeth. Our skin prepares Vitamin D in the presence of sunlight. - Minerals are also needed by our body in small amounts. Each one is essential for the proper growth of the body and to maintain good health. - Calcium and phosphorus build our bones and teeth. Iron is needed to make blood. - Iodine helps in the physical and mental growth of children. We all need vitamins and minerals to remain healthy. But do you know that vitamins get easily destroyed on cooking and washing too much? # Sources of Some Minerals | Mineral | Source | | ----- | ----- | | Calcium and phosphorous | | | Iron | | | Iodine | | | Roughage | | ## Roughage Our body also needs roughage or dietary fibres and water. Roughage is mainly provided by the plant products in our food. Porridge, lentils, cucumber and guava, leafy vegetables are some sources of roughage. Roughage does not provide any nutrient to our body but is helpful in digestion of our food and adds to its bulk. This avoids constipation and helps our body get rid of undigested food. ## Water Water helps our body to digest and absorb nutrients from the food. It also helps in getting rid of waste from the body in the form of urine and sweat. We get water from the liquids we drink, such as water, milk, lassi, lemonade and tea. In addition, we add water to most cooked foods. Fresh vegetables and fruits also provide water to our body. # Check Point Identify and correct the false statements. 1. Carbohydrates get easily destroyed by heat during cooking. 2. Solutions of copper sulphate and caustic soda are used to test the presence of proteins in food. 3. There is also a group of vitamins known as vitamin B Complex. 4. Vitamins and minerals are body-building foods. 5. Carbohydrates give twice as much energy as fats. Does everyone in your family require the same food? Is the food taken by your younger one-year-old brother or sister the same as yours? Does your grandmother prefer the same food as eaten by your uncle who may be 20-25 years of age? Give reasons. # Balanced Diet The food we normally eat in a day is our diet. A balanced diet consists of adequate proportions of proteins, fats, carbohydrates, vitamins and minerals. It should also contain some amount of indigestible fibres or roughage to prevent constipation. No single food item supplies all the essential nutrients in the amounts we need. Therefore, different food items are to be combined to get a proper and balanced nutrition. In a balanced diet, energy giving foods (carbohydrates and fats) in each meal are balanced with body-building foods (proteins) and protective foods (vitamins and minerals). - Cereals and whole grains contain carbohydrates, vitamins and minerals. Wheat flour, of course, is also rich in fibre. - Pulses such as black gram (chana dal), green gram (moong dal) and black gram (urad dal) are good and easily available sources of proteins. Our body requires proteins for building muscles and repair of cells. Proteins act as building blocks and therefore are very important for growing children. Eggs, meat and fish are rich in proteins. - Pulses have some amount of minerals and vitamins. Vegetables, such as spinach (palak), cabbage, cauliflower, lady's fingers or okra (bhindi), tomato and carrot are also good sources of vitamins, minerals and fibres. Carrots are one of the best sources of vitamin A. - Leafy, green vegetables are rich in iron and vitamins. Milk and milk products such as curd, cheese, buttermilk (lassi) are good sources of calcium, phosphorus and some vitamins. Skimmed milk is a better option for elderly persons as it has the same amount of nutrients as normal milk, but with less fat. As far as possible, you should eat seasonal fruits and vegetables. Nowadays, because of the availability of cold storages, vegetables and fruits can be stored for a long time. However, stored foods may lose some of their nutrients during storage. Some disorders of the body are caused by the intake of food items in wrong proportions. Adequate quantities of carbohydrates, fats, proteins, minerals, vitamins and roughage (fibre), as per the requirement of a person, constitute a balanced diet for him/her. The daily diet of a 10-12-year-old child may include two cups of cooked cereals, half a cup of cooked pulses, two cups of milk, a small quantity of green leafy vegetables (cooked or uncooked), a cup of cooked vegetable (locally available) and a seasonal fruit. A child not taking a balanced diet over a long period may get easily tired, have stunted growth and weak eyesight and may be obese. Some schools provide mid-day meals to students. Prepare a diet chart to provide a balanced diet to a twelve-year-old child in this meal. Include food items which are inexpensive and commonly available. # Cooking Right Not just eating the correct food, but correctly prepared food is also very important so that nutrients are not lost. Cooking improves the taste of food and makes it easier to digest. But washing, peeling and over cooking also result in the loss of certain nutrients, especially vitamins and minerals. Some nutrients get lost in the process of cooking and reparation. So, we should follow some simple techniques. - Do not wash vegetables after cutting them. Avoid peeling them as far as possible. - Avoid overcooking or cooking for a longer period than necessary. Use pressure cookers or covered utensils. It will also save fuel. - After washing pulses and rice, if you soak them, do not throw away the water. Use it in your cooking. - Do not keep fruits and vegetables unused after cutting them. Avoid deep frying. # Less or More Food? Both overeating and lack of food intake could be harmful. Sometimes we consume too much chocolates, chips, cold drinks or other foods which are not good for our body. What happens to us after a few days? When we do not eat, our bodies do not get enough nutrition- we feel weak and we are not able to work properly. If we continue to not eat, our bodies start showing signs of illness. This state of the body when we do not get enough nutrition because of less food intake or even eating the wrong food, is called malnutrition. Malnutrition is a state of bad health due to improper intake of food or nutrients. Overnutrition caused by the excessive intake of a nutrient is also a form of malnutrition.. Some diseases such as anaemia, scurvy and rickets are caused due to malnutrition. These diseases are caused due to the deficiency of nutrients. Diseases that occur due to lack of nutrients over a long period are called deficiency diseases. A balanced diet meets all the requirements of our body. You know what happens if any one or more of these are in short supply or are consumed in excess. - Intake of inadequate quantity of proteins or lack of it in diet may slow down growth and development of children. They may also get easily tired. If a child does not get enough proteins in the food for a long time, he/she is likely to have stunted growth, swelling of face, skin diseases and diarrhoea. - Excess of proteins taken over a long period may damage the kidneys. - A lack of carbohydrates leads to lethargy, inactivity and feeling of tiredness. However, excessive intake of carbohydrates may result in obesity and malfunctioning of the breathing system. - Deficiency of fats causes rough skin, weak eyesight and thinness of body. Intake of excess fats leads to obesity. Excess fats make the liver and pancreas less active. - If the diet is deficient in both carbohydrates and proteins for a long period of time, the growth may stop completely. Such a person becomes very lean and thin and so weak that he/she may not even be able to move. Overweight and obesity are the most common results of excessive intake of carbohydrates, fats or even proteins, which results in deposition of fat in tissues of the body. Obesity in children is becoming a common problem nowadays. This is due to excess intake of junk foods like noodles, pizzas, potato wafers, sweetmeats, ice creams and soft drinks. Fast foods lack vitamins and minerals, and proteins. Average person should drink 2-3 litres (about 8-10 glasses) of water every day. People doing regular physical work or those living in hot climates need more water. Those who drink less water may suffer from headache, fatigue, poor mental alertness and kidney stones. Water also helps in keeping the skin healthy. Drinking water kept at room temperature is desirable for good health. Deficiency of different vitamins and minerals may also result in certain diseases or disorders. Some of these are mentioned in the table. Deficiency diseases can be prevented by taking a balanced diet. | Dietary Component | Functions | Sources | Result of Deficiency | | ----- | ----- | ----- | ----- | | Carbohydrates | Instant energy | Sugars - sugar, glucose, sugarcane, honey and milk Starch - wheat, bread, maize, corn, rice and potatoes | Lethargy, weakness | | Fats | Energy banks | butter, lard, sunflower oil, vegetable oils, nuts, almonds, cheese, liver, oils and egg yolk | General weakness, rough skin, weak eyesight | | Proteins | Body building | Flesh (meat, chicken, fish), milk, pulses, egg (albumin and yolk) and cheese | Stunted growth, swelling of face, discoloration of hair, skin diseases and diarrhoea | # Minerals | Mineral | Sources | Name of Deficiency and Symptoms| | ----- | ----- | ----- | | Iodine | seaweed, seafish, onion and iodized table salt | goitre-swelling of the neck| | Iron | meat, liver, egg yolk, fish, green leaves, nuts, fig and pulses | anaemia, weakness, pale appearance | | Phosphorus | meat, fish, milk, cheese, egg, pulses and cereals | rickets in children, weak and soft bones in adults | | Calcium | milk, cheese, curd, fish, eggs, pulses, cabbage and dark green leaves | rickets in children, weak and soft bones in adults | # Check Point 1. Why does our body need nutritious food? 2. Name the different food groups. 3. What are body-building foods? 4. Name three sources of carbohydrates and fats. 5. What are the essential nutrients for our body? 6. Why should we include roughage in our diet?