Chapter 2 — Components of Food

Food is anything we eat or drink to provide our body with useful substances. These substances, called nutrients, include carbohydrates, proteins, fats, vitamins, minerals, water and fibre. Each nutrient has special roles. Together they help us to grow, repair damaged parts, give energy for work and play, and keep our body systems running smoothly. Food is not only fuel but also raw material for building tissues—like how wood and nails build a house, nutrients build the body.

From early childhood food supports rapid growth. Later it maintains body structures, gives energy for thinking and movement, and helps fight infections. A child who eats well usually learns better at school, plays actively and recovers faster from illness. Food also affects appearance: healthy skin, strong hair and bright eyes are signs of good nutrition.

Food choices are important. Different foods are mixtures of nutrients: milk has protein and fat; pulses have protein and fibre; fruits have vitamins and sugar; rice and potatoes have starch. Eating different types of foods is necessary because no single food contains all nutrients in the right amount. This is why meals with variety are important. Cultural habits and family preferences influence what we eat, but the basic need remains the same—get the nutrients required for health.

Food safety and cleanliness are part of why food matters. Food can carry germs that cause diarrhoea or fever if not handled correctly. Simple steps like washing hands, cleaning utensils and cooking food thoroughly reduce risk. This unit will explain each nutrient, how foods are tested for certain components, signs of deficiency diseases, and how to plan a healthy diet for children and families.

Carbohydrates are the main source of energy for the body. Chemically they are made of sugar units. There are two broad groups: simple carbohydrates (sugars) and complex carbohydrates (starch and fibre). Simple sugars like glucose, fructose and sucrose taste sweet and are found in fruits, sugarcane, jaggery and sweets. Complex carbohydrates such as starch are present in cereals (rice, wheat), roots (potato), and legumes. While both types give energy, complex carbohydrates usually release it more slowly and help us feel full longer.

When we eat food with carbohydrates, digestion converts complex starch into simple sugar — mainly glucose. Glucose enters the blood and is carried to every cell. Cells use glucose in respiration to release energy needed for movement, thinking, growth and keeping body temperature. Excess glucose is stored first as glycogen in the liver and muscles. If there is still extra, the body converts it to fat for long-term storage.

Carbohydrates are also important for the brain, which relies mainly on glucose. Not getting enough carbohydrate causes tiredness and poor concentration. Eating too many simple sugars, especially from fizzy drinks and sweets, causes rapid spikes in blood sugar and may damage teeth and lead to excess weight. Choosing whole grains, fruits and starchy vegetables provides energy along with vitamins and fibre. Fibre, a type of carbohydrate the body cannot digest, helps digestion and prevents constipation.

For healthy meals prefer a balance: include a source of starch or whole grains, a moderate amount of natural sugars from fruits, and avoid frequent sugary snacks. This keeps energy steady and supports growth and school activities.

Proteins are essential for growth and repair. They form muscles, skin, hair, nails and internal organs. Proteins are long chains made from small units called amino acids. The body uses amino acids to make its own specific proteins such as enzymes, hormones and antibodies. Some amino acids can be made by the body, but a set called essential amino acids must come from food.

Good sources of proteins include animal foods like eggs, milk, fish, meat and plant foods such as pulses, legumes, soy, nuts and seeds. For vegetarians, combining cereals (rice, wheat) with pulses (dal) over the day supplies most essential amino acids. The quality of protein means how well it provides all necessary amino acids; animal proteins often have higher quality but plant combinations can be equally good when varied.

During digestion proteins are broken down into amino acids which are absorbed into the blood and used to build new body proteins. Growing children, pregnant women and people recovering from illness need more protein. Lack of protein leads to poor growth, muscle wasting, weakness and increased infections. Severe protein deficiency in young children can cause swelling, thin hair and delayed development.

Cooking food makes proteins easier to digest and does not remove their nutritional value. However, very high temperatures for long time can reduce some amino acid availability. Balanced meals with adequate protein, combined with vitamins and minerals, support strong bones, good immunity and healthy development for schoolchildren.

Fats are an important nutrient that provide concentrated energy and help the body in many ways. Per gram, fat gives more than twice the energy of carbohydrates and proteins. Fats form part of cell membranes, act as insulation to keep the body warm, cushion important organs and are needed for absorption of fat-soluble vitamins A, D, E and K. Certain fatty acids are essential and must come from the diet.

Different types of fats exist: saturated fats (found in butter, ghee, fatty meat), unsaturated fats (found in vegetable oils, nuts, seeds, fish) and trans fats (often in hydrogenated oils and many processed snacks). Unsaturated fats, especially from fish, nuts and vegetable oils, are healthier when used in moderation. Saturated and trans fats when eaten too much increase the risk of heart and blood vessel problems later in life.

For children a small amount of fat is essential for brain development and energy reserves. However, excess fat in the diet leads to overweight and related problems. Healthy practices include using small amounts of good quality oils (like mustard, sunflower or groundnut oil), including nuts and seeds occasionally, preferring steamed or baked foods to fried items, and avoiding frequent consumption of packaged fried snacks. Families can reduce unhealthy fats by cutting visible fat from meats, limiting fried food, and choosing low-fat dairy sometimes.

Cooking methods also affect fat intake. Stir-frying with less oil, grilling or baking are better than deep frying. Reading labels for trans fat content becomes useful later on. Overall, include fats for energy and nutrient absorption but in controlled amounts as part of a balanced diet.

Vitamins are organic nutrients needed in very small amounts but they help many body functions. They do not give energy directly, but without them many processes fail. Vitamins are classified as fat-soluble (A, D, E, K) which are stored in body fat, and water-soluble (vitamin C and B-complex) which are not stored and must be eaten regularly.

Each vitamin has special roles. Vitamin A supports good vision, especially in dim light, and keeps the skin and mucous membranes healthy. Vitamin D helps the body absorb calcium for strong bones and teeth; the body synthesises it when skin gets sunlight. Vitamin C helps heal wounds and strengthens the immune system; it is abundant in citrus fruits and guava. B-complex vitamins (such as B1, B2, B3, B6 and B12) help release energy from food and support nervous system function. Vitamin K is essential for blood clotting.

Deficiencies cause recognizable illnesses. Lack of vitamin A can lead to night blindness; vitamin D deficiency causes rickets with soft, curved bones; missing vitamin C causes scurvy with bleeding gums and poor healing. B vitamin deficiencies can cause tiredness, skin problems or poor growth. Most children get required vitamins from a varied diet of fruits, vegetables, milk, pulses and some animal foods. Overdosing on vitamin supplements is not safe without medical advice, especially for fat-soluble vitamins which can build up in the body. The best approach for schoolchildren is a balanced diet with colourful fruits and vegetables to cover vitamin needs naturally.

Minerals are inorganic elements the body needs for structure and function. Unlike vitamins, minerals are simple elements such as calcium, iron, iodine, phosphorus and zinc. They appear in very small amounts in foods but are vital. Each mineral has specific jobs: calcium builds strong bones and teeth, iron helps make haemoglobin in blood to carry oxygen, iodine helps make thyroid hormones that regulate growth and metabolism, and zinc supports growth and wound healing.

Major sources of minerals include milk and dairy for calcium, green leafy vegetables and pulses for iron, iodised salt for iodine, nuts and whole grains for zinc. Different soils contain different mineral levels so plant foods may vary in mineral content. Children need sufficient minerals during growth; lack of iron causes anaemia with pallor and weakness, lack of iodine causes goitre and poor mental growth, and calcium deficiency over time affects bone strength.

Prevention of mineral deficiencies is mainly by a varied diet. Public health measures like adding iodine to salt and iron supplementation programs in schools help reduce common deficiencies. Sometimes doctors advise mineral supplements when diet alone cannot correct a deficiency. However, excessive intake of some minerals can be harmful, so supplements should be taken only when recommended. Families can support good mineral status by offering milk, pulses, green vegetables, nuts and iodised salt regularly to growing children.

Water and dietary fibre are two components often overlooked but very important. Water makes up a large part of our body and is essential for life. It helps dissolve and transport nutrients, removes waste in urine, keeps body temperature stable through sweating, and is part of fluids in which chemical reactions occur. Children lose water faster during play and in hot weather, so they must drink regularly. Clean water also prevents infections; drinking unclean water can cause diarrhoea and other illnesses.

Dietary fibre is the indigestible part of plant foods—found in whole grains, fruits, vegetables, peas and beans. Fibre does not provide energy but has vital roles: it adds bulk to the stool, helps food move through the gut, prevents constipation and maintains healthy bowel function. Fibre also slows down the absorption of sugar after a meal, helping keep blood sugar steady. It helps feel full and can prevent overeating, aiding weight maintenance.

Water and fibre work together. Fibre absorbs water and makes stools soft and easy to pass. If a person eats a high-fibre diet but does not drink enough water, stools may become hard. Good daily habits include drinking plain water frequently, eating seasonal fruits and vegetables, choosing whole grains (like whole wheat chapati or brown rice) and avoiding too many processed, low-fibre snacks. For schoolchildren, carrying a water bottle, eating fruits for snacks and including salad or cooked vegetables in lunch supports digestion and overall health.

A balanced diet gives all nutrients in the right proportions so the body can grow, work and stay healthy. It includes energy-giving foods (cereals, roots), body-building foods (proteins from pulses, milk, eggs or meat) and protective foods (fruits and vegetables for vitamins and minerals). A balanced diet also contains small amounts of fat and sufficient water and fibre. The idea is not one perfect food but a variety across meals and days.

To plan a balanced meal for a child, think of one staple (rice, chapati, dosa), one protein source (dal, egg, paneer), one or two vegetable dishes, a fruit, and milk or its alternative. Snacks should be chosen to add nutrition rather than empty calories—roasted chana, fruit, or a small portion of nuts are better than fried packets. Breakfast is important: idli with sambar and a glass of milk provides grains, protein and vitamins to start the day.

Portion sizes change with age and activity. Growing children and those who play more need more calories and proteins. A weekly plan with variety prevents boredom and supplies different nutrients: include leafy greens a few times a week, seasonal fruits daily if possible, and eggs or legumes several times. For families with budget limits, local seasonal foods and small amounts of animal foods can provide needed nutrients. School menus and lunch boxes should follow simple rules: include a carbohydrate, a protein, a vegetable/fruit and water. Teaching children to eat slowly, to finish a portion of vegetables and to wash hands before meals are small habits that support the benefits of a balanced diet.

Malnutrition occurs when the body does not receive enough calories, protein or essential nutrients for normal growth and health. It can be caused by poverty, lack of food variety, illness, poor feeding practices for infants and children, or repeated infections that reduce appetite and nutrient absorption. Malnutrition can be mild or severe. In children it slows growth, lowers resistance to infections, reduces energy levels, and affects learning and school performance.

There are different forms: undernutrition (not enough calories), protein-energy malnutrition (lack of both protein and calories), and micronutrient deficiencies (shortage of vitamins or minerals). Each shows typical signs. In protein-energy malnutrition, children may become very thin (marasmus) or have swelling of the belly and limbs (kwashiorkor). Iron deficiency causes anaemia with pale skin and tiredness. Vitamin A deficiency leads to night blindness and eye problems. Vitamin D deficiency causes rickets, which shows as soft or bowed legs. Iodine deficiency can lead to goitre (neck swelling) and mental development problems, especially in babies and young children.

Prevention focuses on providing a varied, balanced diet, breastfeeding infants exclusively for the first six months, and introducing safe complementary foods at the right age. Public health measures such as iodised salt, vitamin A supplementation campaigns, and school-based iron and folic acid distribution reduce common deficiencies. Treating infections, improving sanitation and ensuring clean water also help because infections can worsen nutritional status.

Families can take practical steps: include eggs, milk, legumes and green leafy vegetables in meals; offer fruits daily for vitamins; expose young children to sunlight for vitamin D; and avoid over-reliance on one type of food. If malnutrition is suspected, seek help from a health worker or doctor who may recommend special food supplements, fortified foods or medical treatment. Community programmes like mid-day meals and growth monitoring in schools help identify at-risk children early. Early detection and correct feeding can often reverse mild to moderate malnutrition and prevent long-term harm to a child’s growth and learning.

Schools often demonstrate simple, safe tests to identify starch, reducing sugar and protein in foods. These tests help children connect classroom learning to real food items. Always do tests under teacher supervision, use small quantities and follow safety rules such as not tasting chemicals and washing hands after work.

Iodine test for starch: Prepare a small piece of the food or a paste by crushing it. Place a drop on a white surface or a watch glass and add a drop of dilute iodine solution. If starch is present, the colour changes to blue-black. This test works well on potato, rice paste and bread.

Benedict’s test for reducing sugars: Mix a little food extract (juice or water-extract) with Benedict’s reagent in a test tube and heat gently in a water bath. The blue reagent changes to green, yellow, orange or brick-red depending on the amount of reducing sugar present. Sweet fruits, sugar solutions and honey show positive results. Be careful: Benedict’s reagent must be heated and handled by the teacher.

Biuret test for protein: Add a few drops of dilute sodium hydroxide followed by copper sulfate solution (teacher may use a prepared Biuret reagent) to the food extract. A violet or purple colour indicates protein. Milk and egg white give clear positive results. After experiments, dispose reagents as instructed and wash glassware. These simple tests provide practical evidence of components discussed in class and strengthen observational skills and recording results in a simple table.

Foods come from two main sources: plants and animals. Plant foods include cereals (rice, wheat), millets, pulses (dal), vegetables, fruits, nuts, seeds and oils. Animal foods include milk, curd, eggs, fish, meat and poultry. Both groups provide important nutrients. Plant foods are rich in carbohydrates, fibre and many vitamins and minerals; some also supply protein. Animal foods usually supply high-quality proteins, some fats and vitamins such as vitamin B12 which are not found in plant foods.

A healthy diet often combines both sources. For example, rice or rotis (plant-based) with dal (plant protein) and milk or egg (animal protein) gives a mix of nutrients. Vegetarians can obtain all necessary nutrients by combining different plant foods—pulses with cereals provide complete proteins, green leafy vegetables supply iron and vitamins, nuts and seeds give healthy fats. Seasonal fruits and vegetables are especially valuable because they provide fresh vitamins and minerals and are often cheaper and tastier.

Food safety is part of choosing good sources. Fresh milk should be boiled or pasteurised; fish and meat should be cooked thoroughly; fruits and vegetables must be washed well to remove dirt and germs. For families with limited income, small but regular portions of animal foods like egg or milk can improve nutrient intake. Growing kitchen gardens with seasonal vegetables and consuming locally available foods can increase dietary diversity. Teach children to recognise foods from plants and animals and understand which nutrients each source supplies so they can make informed choices at home and school.

Food hygiene means keeping food clean and safe so it does not cause illness. Germs on unclean hands, dirty utensils or contaminated water can lead to stomach infections, diarrhoea or fever. Simple rules help protect health: wash hands with soap before cooking and eating, wash fruits and vegetables well, cook food properly, cover cooked food to keep flies away, and store perishable items in cool conditions if possible.

Avoid cross-contamination by using separate utensils or cleaning the same utensils well after handling raw meats and eggs. Do not reuse food that looks or smells bad; throw away leftovers that have been kept too long at warm temperatures. For drinking water, boil or filter if the supply is doubtful. At school, students should use clean tiffin boxes and drinking bottles, avoid sharing utensils, and eat food within a few hours of preparation.

Food hygiene also involves safe buying and storage. Buy food from clean shops, check expiry dates on packaged items, and prefer freshly cooked meals. For packed school lunches, use insulated boxes or include an ice pack in hot weather, and include items that do not spoil quickly. Teach children to observe colour, smell and texture—if a food looks abnormal, do not eat it. Communities can reduce foodborne illnesses by maintaining clean markets, safe water supply and educating food vendors. Practising good hygiene at home and school lowers sickness, improves attendance and helps children gain the full benefits of nutritious food.

Once food is eaten, the body breaks it down into smaller parts that can be used. This process is called digestion. It begins in the mouth where chewing and saliva start breaking down carbohydrates. Food then passes down the gullet to the stomach where acids and enzymes begin protein digestion. The small intestine is the main site where digestion finishes and nutrients are absorbed into the blood.

Carbohydrates are broken to simple sugars (mainly glucose), proteins to amino acids, and fats to fatty acids and glycerol. These small molecules cross the lining of the small intestine into blood vessels. Blood carries them to cells throughout the body. Cells use glucose and other molecules in a process called respiration to release energy. Amino acids are used to build new proteins for growth and repair. Fatty acids can be used for energy or stored as fat for later use. Water and minerals are absorbed and used for body fluids and structure.

The large intestine absorbs water and forms faeces. Helpful bacteria in the gut break some fibres and make certain vitamins. Good digestion depends on balanced meals, adequate water and fibre, regular eating times and physical activity. Problems such as indigestion, constipation or diarrhoea often result from poor food choices or contaminated food. Teaching children how different foods are digested helps them understand why a varied diet and good habits lead to strong bodies and sharp minds.

Every day children make many food choices. Good choices help them grow, learn and play well. Healthy choices are foods that provide needed nutrients without too much sugar, salt or unhealthy fats. At home, parents can set examples by offering a variety of foods: whole grains, pulses, vegetables, fruits, milk and occasional eggs or fish. At school, children can be encouraged to bring nutritious tiffin boxes and avoid sugary drinks and packaged fried snacks.

Practical tips: include a whole grain or chapati in lunch, add a portion of protein such as boiled egg or dal, include a fruit or raw vegetable, and a small portion of milk or curd. For snacks, choose roasted gram, fruit, nuts or homemade preparations like vegetable paratha. Avoid frequent consumption of sweets and deep-fried items; these provide calories but little nutrition and can lead to weight gain and dental problems. Encourage drinking water instead of bottled sugary drinks.

Children are influenced by advertisements and peers. Teaching them to read simple labels later and to ask questions about food helps build good habits. Involve children in food planning and simple cooking tasks so they feel ownership and are more likely to eat healthy meals. Schools can support healthy choices by providing clean drinking water, offering nutrition lessons and organising activities like kitchen gardens. Small, consistent choices at home and school create lifelong healthy habits that protect against disease and support learning and growth.