We all need food to grow and work. It gives us energy to speak, think, work and play. In fact, our body is built up from nutrients that come from the food we eat. Different foods help us in building our body in different ways. Some of the foods that we should take regularly are milk, fruits, vegetables, dal, rice and chapatti. Milk makes our bones strong. Fruits and vegetables help our body to fight germs and keep us healthy. Legumes provide us with essential nutrients such as proteins, carbohydrates, vitamins, minerals and dietary fibre while cereals are a good source of complex carbohydrates vitamins such as thiamine, riboflavin and niacin. A food with a great taste may not be good for the body. Similarly, food which is not so good to taste may be very useful for our body.
Nutrients
Nutrients are necessary for maintaining a healthy body and proper growth. They give us energy for our daily activities, keep us away from diseases, build muscles and help us grow strong and healthy. The food we eat contains nutrients such as carbohydrates, fats, proteins, fibre or roughage, water, vitamins and minerals. These are discussed as follows: Carbohydrates (Sugars, starches and cellulose, all made up of carbon, hydrogen and oxygen) are required by our body to get the necessary energy required for its functioning and other activities Sources: We get carbohydrates through food items such as bread, rice, wheat, maize, millets (bajra, jowar), potatoes, sweet potatoes and sugarcane. People who are physically very active, such as a sportsperson, a labourer, army and farmers, need more carbohydrates. Energy from 1 gm of carbohydrate = 4 kilocalories. Carbohydrates are broken down into sugars (mainly glucose) and oxidised to get energy. Fats (Made of carbon, hydrogen and oxygen) Extra food is stored by the body in the form of fats in the liver and under the skin. Body needs fats as a source of energy, to keep itself warm, dissolve and use fatsoluble vitamins such as vitamin A, D, E and K. Sources: Food items like milk, vegetable oil, fish liver oil, ghee, nuts, butter, cheese contain this nutrient. Fats provide more energy than carbohydrates. Energy from 1 gm of fats = 9 kilocalories. Cosuming excessive fat with no exercise and physical work leads to obesity. Hormonal imbalance is also one of the causes of obesity. Obesity gives way to several other diseases such as fatty liver, heart problems and joint pain.
Proteins (Made of nitrogen containing compounds called amino acids) are bodybuilding nutrients that are needed for strong muscles, growth and repair of body parts, from skin to bones. Sources: Food items such as milk, cheese, pulses, soyabean, eggs, fish, meat, poultry contain this nutrient. Protein requirement changes with change. Growing children need more proteins than the adults. In the absence of fats and carbohydrates (during starvation) proteins break up to provide energy to the body. Energy from 1 gm of proteins = 4 kilocalories. Vitamins and Minerals are required to protect us from diseases and stay healthy. For example, the mineral iron is require for blood while calcium for strong bones and teeth. Similarly, vitamin K is needed for blood clotting while vitamin C for healing from cuts and scratches. Sources: Food items such as green vegetables, milk, eggs and peanuts contain vitamins and minerals. Most vitamins and minerals are especially plentiful in fresh fruits and vegetables. Vitamins and minerals are micronutrients as required by the body in smaller amount, compared to the macronutrients, carbohydrates, proteins and fats. Vitamins and Minerals Deficiency Diseases
| Vitmains/ Minerals | Food sources | Deficiency Diseases | Symptoms |
| Vitamin A | Milk, butter, cheese, fish oil, eggs, vegetables (carrot, yellow pumpkin, spinach and sweet potato) papaya and mangoes | Night blindness | Poor vision, loss of vision in darkness |
| Vitamin B1 | Milk, cheese, wheat, gram, beans, peanut, yeast, leafy vegetables, meat and liver | Beriberi | Weak muscles, fatigue |
| Vitamin C | Citrus fruits (amla, orange, lemon, tomatoes, pineapple), leafy vegetables and sprouted grams | Scurvy | Bleeding gums, wounds take long time to heal |
| Vitamin D | Sunlight, milk, egg yolk, fish liver oil, cheese and butter | Rickets | Bones become soft and bend easily |
| Calcium | Milk, green vegetables, gram and fish | Osteoporosis (Bones and tooth decay) | Weak bones, tooth decay the neck gets swollen, mental disability in children |
| Iodine | Iodised salt | Goitre | Thyroid gland in |
| Iron | Green leafy vegetables like spinach, chenopodium, methi, amla and jaggery | Anaemia | General weakness, fatigue |
Roughage is neither digested nor absorbed for any energy requirement into the body but it helps in easy bowel movement and so keeps the digestive system working well. It is not digested by the human body because the cellulose digesting enzyme (cellulase) is absent in the human body. Roughage is also known as dietary fibre. Source: It is found mainly in wholemeal bread, fresh vegetables and fruits as cellulose (complex carbohydrate made of glucose molecules) in their cell wall. Water is important for proper functioning of the body. We should drink plenty of water every day. 60% of an adults human body and 75% of an infants body is water. It helps in transportation and digestion of food material, excretion of wastes, maintenance of body temperature, etc. It acts as a solvent for various reactants and products in the body.
Test For Presence Of Starch, Protein Or Fats In Food
We can test for the presence of starch, protein or fats in a given food item by the following simple tests: Take a small sample of the food item. Pour 2-3 drops of dilute iodine solution on it. If it turns blue-black in colour, it contains starch. Make a powder/paste of a small amount of food item and put it in a clean test tube. Add a little water and stir. To this add 2 drops of copper sulphate solution and 10 drops of caustic soda solution. Shake well and let the mixture settle down for some time. Presence of violet colour signifies the presence of proteins. Take a small quantity of the given food item in a piece of paper. Fold the paper and crush the food item present in it. Open the paper. If the food item leaves an oil patch on the paper, it contains fats.
Balanced Diet
The food that we eat on a daily basis forms part of our diet. However, not all nutrients are present in every food item. To fulfil our nutrient requirements, we need various kinds of nutrients as our body’s need cannot be fulfilled by one kind of food. The
group of foods that we eat every day is called diet. A balanced diet is a diet that contains all the nutrients including fibre or roughage and water in the right amount. To stay away from diseases and live a healthy life we should eat a balanced diet.
How We Eat Food
Some foods are eaten uncooked and some are eaten after being cooked. An apple or an orange is eaten uncooked. We must clean the food properly with clean water before eating. Potatoes, rice and eggs are some foods that are cooked for eating. Cooking kills germs in the foods. A cooked food is easily digested by our body. Before eating uncooked food or before cooking make sure of the following points:
• Don’t wash fruits and vegetables in unclean water.
• Don’t wash fruits and vegetables after cutting them.
• Don’t throw away the water in which rice or cereals are cooked.
• Don’t overcook the food; it will destroy the nutrients in the food. The food that we eat is not directly taken up by our body. Our body has a set of organs that process the food and make it usable. We chew food with our teeth. We have two sets of teeth in our life time: temporary teeth and permanent teeth. The temporary teeth (milk teeth) are also called baby teeth or milk teeth and are 20 in number. The secondary teeth are also called adult teeth and are 32 in number. Milk teeth are usually replaced by adult teeth between the ages of 6 and 12.
Teeth
Each tooth has two main parts. The upper one is the crown, which is seen above the gum. The lower part is the root, which fixes the tooth firmly in the jawbone. Incisors, canines and premolar teeth have one root each. Molars have two or even three roots. Enamel: It is the hardest substance in our body. It is the hardest tissue in our body and has no living cells. Dentine: It is sensitive to cold and heat. It is stronger than bones. Pulp: It is the soft tissue that lies at the core of the tooth, that is within dentin. It contains blood vessels, which bring nutrients for the tooth, and sensitive nerves that warn if you are biting too hard, or if a toothache is about to start. According to their functions, teeth are classified into: incisors, canines, premolars and molars: Incisors: They are used to cut food. There are four incisors in each jaw. Canines: They are used to tear food. There are two canines in each jaw, next to the incisors. In carnivorous animals, canines are bigger and sharper so that they can easily tear flesh. Premolars: They are used to grind food. There are four premolars in each jaw next to the canines.
Molars: They are used to grind. There are six molars in each jaw. They have a large flat surface and are bigger and stronger than the other teeth. Out of all the molars, four grow later and are called wisdom teeth.
Digestive System
Food needs to be digested or broken down before our body can use its nutrients. Most nutrients in food are chained, or linked together. Our teeth, stomach, liver, and intestines break the chains so the nutrients are free to travel to different parts of our body. These organs are all part of our digestive system. A group of organs that work together make a system. An organ is a part of our body that has a specific job to do. Digestion begins in the mouth. The teeth help in chewing the food and the tongue mixes the food particles with saliva. Saliva is a digestive juice produced by the salivary glands. The food in the mouth is softened and moistened so that it can be swallowed easily. The food that has been swallowed passes into the oesophagus. It is a tube through which food passes from the mouth to the stomach. The stomach is a sac-like organ that squeezes and breaks the food into smaller particles. From the stomach the food passes into the small intestine. The broken down food particles are absorbed by the blood an vessels in the walls of the small intestine. The blood carries this food to different parts of the body. The undigested part of the food moves to the large intestine. Water from this undigested food is absorbed here and the waste product called faeces is formed. The unwanted waste or faeces is expelled from the body through the anus. The liver and the pancreas work with the small intestine in the digestion process. The liver provides bile that breaks the fat into smaller bits. The pancreas produce juices called enzymes that help in breaking down of some foods.
Preservation Of Food
Food gets spoiled if left open for a long period of time. Microorganisms such as bacteria, yeasts and enzymes present within the food may cause it to spoil. Therefore, we need to preserve food to store it for a long duration of time. Some ways of preserving food are drying, pickling, refrigerating, deep freezing and canning or bottling. Vegetables can be preserved for days by refrigerating while fish and meat can be preserved by deep freezing. Sauces and jams are stored in cans and bottles while nuts and grapes can be dried. Pickles of mango, lemon and other vegetables are made with oil and salt for preservation.
Healthy Eating Habits
Our digestive system is the cornerstone of good health. We should develop the following habits to help our digestive system work properly:
• Wash hands properly before and after eating.
• Always eat in relaxed and comfortable environment.
• Never do any other work while eating.
• Eat slowly to chew food thoroughly.
• Eat healthy and ample breakfast so that energy level is maintained in the body throughout the day.
Food Habits In Animals
According to their feeding habits, animals can be categorised into three groups: herbivores, carnivores and omnivores. Animals that eat only plants are called herbivores, those that eat the flesh of other animals are called carnivores and those that eat both plants and other animals for their food are called omnivores. Herbivores are considered a bridge between plants that prepare food and carnivores. The energy required by carnivores is found in food prepared by plants. This food is taken in by herbivores, which in turn becomes the energy source of carnivores.
Water
Water is a renewable resource and is very important for the sustenance of life. Almost three-fourth of the Earth’s surface is covered with water in the oceans, seas, lakes and rivers and, as ice and snow, in the ice sheets at the North and South poles. 97 per cent of the total water present in hydrosphere, is present in an unusable form in oceans. Fresh water constitutes only 3 per cent, out of which 72.2 per cent is in the form of frozen ice caps and glaciers; 22.4 per cent comprises ground water and soil moisture while rivers, lakes, streams, etc. constitute the remaining 0.36 per cent. There are also huge quantities of water in the air in the form of clouds or the invisible gas (water vapour). Water is very essential for all living beings, as the entire cellular process take place in the medium of water and the flow of materials that occurs from one part of the body to another part happens in solute condition.
Importance Of Water
The importance of water is discussed as follows:
• It is a universal solvent.
• It transports mineral salts from one to another part of the plant.
• It forms the main protoplasm constituent.
• It plays the role of reactant in multiple metabolic reactions.
• It is essential for plants for the process of photosynthesis.
• It maintains the turgidity of growing cells.
• Cell growth occurs during the elongation phase due to absorption of water.
• It is the metabolic end product of respiration.
• It is important for various purposes such as thermal power generation, irrigation, livestock management, industries, domestic needs, hydro-electric generation and transportation.
Shelter
Shelter generally refers to habitats of animals and humans. Animals and humans choose a suitable shelter for themselves from a comfort, safety and developmental point of view. Shelters can be of various types, such as bus shelters, bomb shelters, band shells, houses, tents, house boats, huts and caves. The most common shelter for people are the houses. Generally, a house is made up of cement, brick, sand and stone. It protects us from heat, cold and rain. It also protects us from wild animals and harmful insects. Some of the characteristics of a good house are:
• It should be clean and tidy.
• It should be airy.
• It should be well lit.
• It should be safe.