Class 12 Physical Education Chapter 2 Sports and Nutrition

It is well known that food is essential for survival. Food refers to any substance that nourishes our body or in other words, it is anything that we can digest, absorb and utilize, for various physiological functions of the body including growth and development. Since the time of conception in the mother’s womb, providing energy for our sustenance, regulating activities of the body and repairing day to day wear and tear, the role of food is enormous. Food provides nutrition to the body.

Hence, Nutrition is the science of food and a study of the process that includes everything happens to food from the time it is eaten until it is used for various functions in the body. It is the scientific study of foods and the nutrients therein; their action and interaction and balance, in health and diseases. It is the study of ingestion, digestion, absorption, utilisation and assimilation of nutrients present in food. When we see any food product we recognise it as chapatti, rice, dhal, ladyfinger, apple etc. but as the food enters our mouth it starts breaking down and our body identifies it as different chemicals present therein. These chemical substances which are present in food are called nutrients. Nutrients include carbohydrates, proteins, fats, vitamins, minerals, water and fibre (roughage).

Different food stuffs contain these nutrients in different amounts and proportions and our body needs each nutrient in a certain specific amount for various physiological functions and overall growth and development. Nutrients, as mentioned earlier are those chemical substances in foods that are required by the body for energy, growth and maintenance. Nutrients can be broadly classified as macroand micro-nutrients depending upon their daily requirements by the body. Some nutrients are needed in larger amounts, these are called macronutrients. Nutrients like Carbohydrates, proteins and fats along with water are macronutrients. Other nutrients like vitamins and minerals are required in small amounts and are called micronutrients.

Although these are required in smaller amounts but they are all equally essential for our health. Each of these nutrients plays a significant role in the body. Macronutrients are required by the body in relatively large amounts. Carbohydrates, proteins and fats are macronutrients and are also called ‘proximate principles’ because they form the main bulk of the diet. In Indian meals, they contribute to the total energy intake in the following proportion: carbohydrates: 55-60%; protein: 10-15% and fats: 20-30%. Water does not provide energy but is a vital nutrient required in large quantity for functioning of metabolic processes in the body and various regulatory functions. Therefore, it is also considered a macronutrient.

Carbohydrates are organic compounds made up of Carbon, Hydrogen and Oxygen. Carbohydrates are a major source of energy and provide 4kcal per gram. Carbohydrates are found in abundance in plant foods. There are three types of carbohydrates mono saccharides, disaccharides and polysaccharides. Monosaccharides are simple single units of sugars like glucose, fructose and galactose. Disaccharides are when two monosaccharides are combined together; these are maltose (glucose + glucose), lactose (glucose + galactose) and sucrose (glucose + fructose). Simple sugars (mono and disaccharides) are found in fruits (sucrose, glucose and fructose), milk (lactose) and sweets that are produced commercially and added to foods to sweeten, prevent spoilage, or improve structure and texture.

Polysaccharides are more than two units of monosaccharides joined together. These are starches and fibre (cellulose). These are also called complex sugars and are found in whole grain cereals, rice, oats, potatoes, bread, legumes, corn and flour. All these carbohydrates have to be broken down to the smallest unit ie., glucose to get absorbed and utilised in the body. However, cellulose and other large carbohydrate molecules cannot be digested in the human digestive tract, and are termed as fibre or nonavailable carbohydrates. Sugars and starches can be digested and utilised for various bodily functions, hence are known as available carbohydrates. Diets rich in complex carbohydrates are healthier than low-fibre diets based on refined and processed food.

Proteins are organic compounds containing nitrogen, besides, carbon, oxygen and hydrogen. Protein molecules have a complex structure, and are made up of nitrogen containing amino acids. Amino acids are linked together in chains to make different type of proteins in the body. From hair to nails, muscles to skin, organs to blood, hormones to enzymes, protein is a major structural and functional component of our body. There are around 20 amino acids joined together in varying sequences to form different kinds of proteins. There are nine amino acids which cannot be synthesized by the body; these are called Essential Amino Acids (EAA). Others are nonessential amino acids as these can be synthesized in the body. Depending on the availability of these essential amino acids in foods, they are classified as complete protein foods, partially complete protein foods and incomplete protein foods. Complete protein foods are those which contain all essential amino acids in adequate amounts. These food sources include foods from animal sources like eggs, milk and milk products, meat and meat products and a plant source, soybean, that contains all essential amino acids.

Protein quality is determined by the presence of complete protein foods in the diet; it improves the absorption and utilization of protein in the body. Partially complete protein foods are those which are lacking in any one essential amino acid eg., cereals and pulses. Cereals lack lysine and pulses lack methionine. To improve the protein quality, cereals and pulses can be taken together in a meal or can be combined with sources of complete protein foods. Incomplete proteins are those which are lacking in more than one EAA.

Lipids or Dietary Fats a broader term used for both oils and fats. Oils are basically liquid at room temperature and fats are solid at room temperature. It is the presence of different types of fatty acids which make them liquid or solid. Fatty acids are classified as Saturated or Unsaturated Fats depending upon the presence of double bond in their chemical structure. Saturated fatty acids (SFA) contain no double bonds, monounsaturated fatty acids (MUFA) contain one, and polyunsaturated fatty acids (PUFA) contain more than one double bond.

When the percentage of saturated fatty acids is higher, the fat is solid at room temperature and when the percentage of unsaturated fatty acids (MUFA or PUFA) is higher the lipid is liquid at room temperature and is called oil. Saturated fats which are also called as animal fats are associated with increased health risks. It has been recommended that the intake of saturated fats be kept less than 7% of total calories. Desi ghee, butter, cheese, cream, red meats, baked products, and other full-fat dairy products are the main sources of saturated fats in most diets. Coconut and palm oils also contain saturated fats. Monounsaturated and polyunsaturated fatty acids are unsaturated fats. When they replace saturated fats in the diet, they help to reduce blood cholesterol levels and thus lower the risk of heart disease. Canola, olive, peanut, palm olein, rice bran and til (sesame) oils and other nuts like walnuts are rich in monounsaturated fats. Sources of PUFA include vegetable oils, mustard, soybean, corn, safflower and sunflower oils and flaxseed. Visible sources are ghee, butter, cooking oil etc. while invisible sources include nuts, cereals, pulses, milk, eggs, meat etc.

Invisible fat contributes significantly to the total fat and essential fatty acid content of diet depending on the food stuffs present in the diet. The total fat (visible + invisible) should provide between 15-30% of total calories required and contribution of visible fat should be restricted to 20-30g per day depending upon the physical activity levels of the individual.