 Welcome back, so all these previous classes we have seen the general introduction about the nutrients, then the digestion absorption of nutrients and the recommended dietary allowance. Now let us start going into each nutrient in detail starting with the major nutrients out of which carbohydrate is the main major nutrient among the three carbohydrates, proteins and fats. So, the general characteristics of carbohydrates, the term carbohydrate is derived from a French word hydrate de-carbon. So, it is composed of carbon, hydrogen and oxygen and the empirical formula is CH2O. Our body derives energy from the catabolism of energy yielding nutrients like the carbohydrates, fats and proteins. So, carbohydrates are the single most abundant source of dietary energy which comprises 50 to 70 percent of the total energy intake of our diet. So, any area population you see the carbohydrate is the major content giving the energy. Now, let us see the classification of carbohydrates. So, these are diverse organic molecules, they can be classified based on their molecular size or degree of polymerization and their digestive fit. So, classification based on the degree of polymerization, they are classified into monosaccharides, disaccharides, oligosaccharides and polysaccharides. So, monosaccharides they are consisting of single unit of sugar and they are also known as simple sugars. So, the degree of polymerization is 1 and they cannot be further hydrolyzed and disaccharides consists of two monosaccharides where the degree of polymerization is 1 to 2 and oligosaccharides the polymerization is 3 to 9 and you can get so many monosaccharide units when they are hydrolyzed. Polysaccharides each molecule contains more than 9 degree of polymerization and you get several molecules of monosaccharide units and classification based on the digestive fit of carbohydrates. So, the digestive fit of carbohydrates depends upon their inherent chemical nature and the supra molecular structures within the foods of which they are a part. So, they are classified as available and non available or unavailable carbohydrates. So, carbohydrates that are digested to constituent monosaccharides and absorbed fall under the category of available carbohydrate. Whereas, the carbohydrates that are not digested by the endogenous enzymes and we have do not have the capacity of digesting those carbohydrates in the intestinal tract they are classified as unavailable carbohydrates. So, these undigested carbohydrates they finally enter the colon we cannot separate digested and undigested carbohydrates and eat. So, we eat food totally. Therefore, the undigested carbohydrates they reach the colon and here they are fermented by the micro flora that are present in the intestines. Therefore, unavailable carbohydrates are not really unavailable, but they are termed as non-glycemic carbohydrates. That means, they do not provide any energy or in the stomach and they go undigested into the intestines. Now, functions of carbohydrates the main function of carbohydrate is they are the source of energy and glucose is the main source of energy to the body cells. One gram of carbohydrate provides 4 kilo calories of energy I have been repeatedly telling this so that you do not forget and energy is required for normal functioning of organs in the body and the glucose is stored in the liver as glycogen. So, liver is the storage organ for glycogen and whenever the body requires glucose the glucose is released from the liver and the levels in the blood are maintained. Then protein sparing action. So, carbohydrates help in regulating the protein metabolism because the main function of protein is to building up of the body and repair of tissues. So, but protein also provides 4 kilo calories of energy. So, if carbohydrates are not provided proteins will start giving energy. Therefore, when you give sufficient amount of carbohydrates proteins are spared for their functions that is this protein sparing action. Now therefore, the patients who are unable to eat temporarily we give them some dextrose intravenously. So, that proteins are not spared then they have an anti ketogenic effect. The presence of carbohydrates is also necessary for the fat metabolism without carbohydrates fats also are not digested. Then excretion of toxin, glucuronic acid which is a metabolite of glucose it combines with chemical and bacterial toxins and some normal metabolites in the liver and thereby it helps in excretion. So, carbohydrates also help in the excretion of toxins that are present in the body then they act as precursors. So, carbohydrates and their derivatives are precursors to the compounds such as nucleic acid, connective tissue matrix and galactoside of nervous tissues and they are generally required for overall health of the individual. So, non-glycemic carbohydrates I told you which are not digested in the body including non-starch polysaccharides these because they are not digested they can be utilized for beneficial purpose like the function of gastrointestinal tract is improved because when you have undigestible carbohydrates they start absorbing more water and help in the regular peristalsis of the gastrointestinal tract prevent from constipation. So, like this they have a positive effect on the health of an individual. Now, what are the four sources of carbohydrates you have all the grains cereal grains then you have sugar is the concentrated source I mean the it is the only source of carbohydrate if you take one teaspoon of sugar 1 teaspoon contains 5 grams and you will get multiply into 4 you get 20 kilo calories directly as kilo calories. Then you have some amount in fruits and vegetables then you have in milk meat egg and say all the foods and pulses nuts and cereals oil seeds potatoes roots and tubers and these beans and other roots and tubers all these are rich foods of carbohydrates. Now, dietary carbohydrates and blood glucose since we are saying it is a glucose blood glucose has to be maintained to maintain normal health otherwise you become diabetic. So, some carbohydrate containing foods like pure source of glucose they produce rapid rise in the glucose or followed by the blood glucose concentration is steeply falling down like after taking a meal if the curve goes like this. So, within half an hour you have a steep rise in the blood glucose curve and it falls very fast then what happens you feel giddy is not it. So, foods with low glycemic index tend to create a sense of satiety satiety is satisfaction. That means, you have more of unavailable carbohydrates or undigested carbohydrate then you have a feeling of fullness you eat fibrous food. So, this takes over a long period of time and releases the glucose very slowly into the blood. So, therefore, at the same time you also limit the calorie intake. So, this is how the glycemic index is carried on. So, it is defined as the area under the blood glucose curves and which is seen after the digestion of a meal by taking the carbohydrate rich meal and it is compared to the area under curve of glucose. So, when you compare these two you have the glycemic force. If there is a steep rise in the curve then it is said to be high glycemic index which is not good for health. So, you always have to take low glycemic index foods to have a healthy normal blood glucose levels in the body. So, requirement of carbohydrates, carbohydrates are not essential nutrients because the carbon skeletons of amino acids can be converted into glucose. I told you the protein also can be converted into energy. So, they are not called as essential nutrient. However, when you do not take sufficient amount of carbohydrate it leads to ketone body protection. So, the ketonic acids are produced because it does not help the assimilation of fats and there is degeneration of body protein. So, where the role of protein is to provide body building functions otherwise it is providing energy. So, it protects the proteins. The requirement the RDFO carbohydrate is set as 130 grams per day for adults and children. So, adults should continue the main thing is it should give 45 to 65 percent of the total calories that is taken per day and it is recommended that added sugar represent should not be more than 25 percent of total energy because it may dispense the other nutrient rich foods from the diet. Once you take in a more than 25 percent of sugar in your diet you do not feel like taking the other food. So, it dispenses the other foods. So, thereby it leads to deficiency of certain micronutrients. Now, simple sugars and disease the consumption of simple sugars is harmful that is pure sugar is harmful because generally say that whenever we take high amount of sugar it leads to diabetes or hypoglycemia that is wrong. So, carbohydrates are not inherently fattening unless you take excess amount of carbohydrates the energy is stored as fat, but naturally they are not fattening and result in fat synthesis only when consumed in excess in the body. However, there is an association between sucrose consumption and dental caries because it attracts all the bacteria on the teeth and forms cavities on the teeth. So, this is about the carbohydrates the structure of carbohydrates the classification of carbohydrates then the food sources the requirements and the deficiency or excess of carbohydrates how it leads to diseases and how it hampers the health. Thank you.