Our diet contains many food items which are obtained from different sources. The food may be obtained from animal or vegetable sources. We already know that food comprises constituents like proteins, carbohydrates, fats and supplementary substances such as minerals, vitamins and water that are vital for life. These constituents are known as nutrients. For proper functioning of our body we need to consume body building foods (e.g. milk, meat, poultry, fish, eggs, pulses, groundnuts); energy giving foods (e.g. cereals, sugar, roots, fats and oils); and protective foods (e.g. vegetables, fruits).
Nutrients
The food we consume breaks down to simpler products before it is absorbed and utilised by the body. These simpler substances are called nutrients. Our body utilises nutrients for building and repairing, obtaining energy and for protection from diseases. What is nutrition? The term nutrition is related to our food intake and dietary patterns and utilisation of protein, carbohydrate, fat, vitamins and minerals to maintain our health. Most of the natural food items contain more than one nutrient. Let us understand various nutrients contained in different food items.
Proteins
Proteins are called building blocks of our body. About 20 per cent of our body weight comes from proteins. Proteins are essential for growth and repair of muscle and other body tissues. Proteins are made of amino acids that contain the elements carbon, hydrogen, oxygen and nitrogen. We obtain proteins from animal as well as vegetable sources. Proteins of animal origin are found in milk, eggs, cheese, fish and meat. Proteins from these sources contain all the essential amino acids (EAA) in adequate amounts. Vegetable proteins are found in pulses (legumes), cereals, beans, nuts, oilseeds, etc. Those who take vegetarian food need to consume more and a wide variety of these foods to meet their protein needs.
Carbohydrates
Carbohydrates are the main source of energy for our body. There are three major categories of carbohydrates, viz. starch, sugar and cellulose. Our body breaks down sugar and starch into glucose to provide energy. Cellulose does not have any nutritive value per se, but is a major contributor of dietary fibres. Excess carbohydrates are converted into fat by the liver and stored in the adipose tissues in our body.
Carbohydrates are of two types – simple and complex. Simple carbohydrates are quick energy foods, e.g. sugar. Sources of simple carbohydrates are natural fruits, milk and milk products, and vegetables including potatoes and carrots. Complex carbohydrates are better sources of energy than sugar since these are released slowly. Sources of complex carbohydrates are breads, cereals (rice, wheat, bajra, corn, barley, ragi, etc.). We should consume starch and natural sugar and eat whole grains, rice, bread, cereals and fruits to obtain adequate amount of carbohydrates. Fast food items such as pizza, pasta, noodles, etc. are rich in carbohydrates only and cannot replace a balanced meal.
Fats
Fats and oils are concentrated sources of energy. Fats are substances that our body stores for future use. These are classified as simple lipids (e.g. triglycerides), compound lipids (e.g. phospholipids), and derived lipids (e.g. cholesterol). Fats may be obtained from animal or vegetable sources. The major sources of animal fats are ghee, butter, milk, cheese, eggs, fish and meat. The sources of vegetable oils are groundnut, mustard, sesame, coconut, etc. Excess carbohydrates are converted into fats. Fast food items like pizza, samosas, burgers are rich sources of fat. Therefore, children who consume only fast food items tend to become obese.
Vitamins
Vitamins are organic substances that we require in adequate quantities for good health. Our body, however, cannot synthesise them. Therefore, we need to consume their natural sources such as fruits and vegetables. Vitamins are divided into two groups–fat soluble vitamins (Vitamins A, D, E, and K) and water soluble vitamins (Vitamins of B group and Vitamin C). Each vitamin has a specific function and its deficiency leads to a particular deficiency disease.
Minerals
Minerals are the nutrients that are very essential for proper growth and functioning of our body and are required in small amounts. Calcium, Chlorine, Copper, Fluoride, Iodine, Iron, Magnesium, Manganese, Phosphorus, Potassium, Sodium and Zinc are essential mineral nutrients.
Some of them are explained below.
Vitamins — Sources, Need and Deficiency Disease
Fat soluble Vitamins
| Name of Vitamin |
Sources |
Need |
Deficiency Diseases |
| Vitamin A |
Milk, butter, egg, carrots, cod liver oil, tomatoes, pumpkin, green leafy vegetables |
Normal growth and to keep eyes and skin healthy |
Night blindness, Irregular growth of teeth |
| Vitamin D |
Cheese, butter, milk, green vegetables, fish liver oil, sunlight |
Formation of strong bones and teeth |
Rickets |
| Vitamin E |
vegetable oils, spinach, lettuce, turnip leaves, butter, milk, whole grains, nuts, seeds, leafy vegetables |
Protection of cell membrane, formation of red blood cells (RBC) |
Not yet confirmed |
| Vitamin K |
Cabbage, cauliflower, spinach and other green leafy vegetables, cereals, soyabeans |
Clotting of blood |
Excessive bleeding from wounds |
Water soluble Vitamins
| Name of Vitamin |
Sources |
Need |
Deficiency Diseases |
| Vitamin B1 (Thiamin) |
Seafood, milk, meat, peas, cereals, green vegetables |
Growth and development, releasing energy from carbohydrates |
Beri beri |
| Vitamin B2 (Riboflavin) |
Yeast, egg, meat, peas |
Body growth and red cell production, releasing energy from carbohydrates |
Skin diseases, retarded growth |
| Vitamin B3 (Niacin) |
Whole cereals, tomatoes, potatoes, meat and fish |
Healthy skin, digestion and nervous system |
Pellagra (affects skin, alimentary canal and nervous system) |
| Vitamin B12 |
Liver, milk, eggs, fish |
Forming RBC |
Anaemia |
| Vitamin C |
Indian gooseberry (amla), lemons, lime, pineapple, oranges, watermelon, green peppers, tomatoes, cabbage, turnip, carrots, green mint, guava |
Maintenance of ligaments, tendons, other supportive tissues and blood vessels |
Scurvy (gums swell and bleed) |
Water
Water is a nutrient and it makes up almost 70 per cent of our body weight. We need water to break down complex food molecules, and transport food, chemicals and gases throughout the body. It acts as the medium for biochemical reactions and is also required to eliminate the wastes as urine and sweat. We should take 8 – 10 glasses of potable water per day. Inadequate water intake leads to dehydration. Therefore, intake of water in proper proportion is important. We should never substitute water with coffee, tea or soft drinks.
Important Minerals — Sources and Functions
| Name of Mineral |
Sources |
Need |
| Iron |
Meat, fish, liver, eggs, green vegetables, turnip, germinating wheat grains and yeast Milk and milk products, green leafy vegetables. |
Formation of haemoglobin |
| Calcium |
Milk and milk products, green leafy vegetables. |
Formation of strong bones, teeth; clotting of blood; muscle contraction. |
| Phosphorus |
Meat, egg, fish, whole grains |
Development of strong bones, teeth; making energy-rich compounds in cells. |
| Potassium |
Green and yellow vegetables |
For growth; keeping cells and blood healthy. |
| Sodium |
Common salt, also in meat and milk products |
Proper functioning of nervous system. |
| Iodine |
Iodised salt, seafood and water |
Proper functioning of thyroid – deficiency causes goitre. |
| Fluoride |
Coffee, spinach, onion and tea |
Makes enamel of teeth hard and prevents dental caries. |
| Copper |
Grains, nuts and chocolate |
Helps in formation and functioning of RBC, connective tissue and nerve fibres. |
| Zinc |
Meat, eggs and fish |
For insulin production, digestion, metabolism; functioning of male prostate. |
| Chloride |
Meat, milk products and fish |
Functions of muscles and nerves and digestion. |
