Carbohydrates Unit 2nd of Nutrition

Carbohydrate Unit 2nd of Nutrition for BSc Nursing and GNM Ist year

1. Unit 2 nd Nutrition

2. Objective Definition of carbohydrate Classification of carbohydrate Daily requirement Dietary source Function of carbohydrate Digestion , absorption and storage of carbohydrate Metabolism of carbohydrate Deficiencies due to carbohydrate Over consumption of carbohydrate

3. Introduction Carbohydrate is the main source of energy and forms the bulk of our diet. They are available in the market in the natural form, processed form or modified form as an additive in many different products. Carbohydrate holds a great part of our Indian diet.

4. Definition :- Carbohydrate are polyhydroxy aldehydes or polyhydroxy ketones or substances that yield such compounds on hydrolysis. Carbohydrates are organic compounds made up of carbons, hydrogen and oxygen. They are called carbohydrates because they contain hydrogen and oxygen in same proportion as found in water i.e ; 2:1 Caloric value of carbohydrates is 4 kcal

5. Classification of carbohydrates C arbohydrates are classified on the basis of the number of sugar units or saccharide units which are present in their structures.

6. Monosaccharide Monosaccharide also called  simple sugar , are the simplest form of  sugar  and the most basic units of  carbohydrate .  They cannot be further  hydrolyzed to simpler chemical compounds . The general formula is  C 6 H 12 O 6(Glucose) . They are usually  colourless,  water-soluble, and crystalline solids. Some monosaccharide's have a sweet taste.

7. Cont… Glucose :- It is the most important of all the monosaccharide's as it is the primary carbohydrate used by the body. Glucose is the sugar which is absorbed into the bloodstream after carbohydrates are digested in the body. It is also known as dextrose and available in powder and liquid form.

8. Cont … Fructose :-It is the sweetest of all sugars and is also known as fruit sugar because it is found in fruits and honey. In human body, it is converted to glucose and oxidized as a source of energy. It is also called levulose . Galactose- It is found in combination with glucose in milk. This sugar is converted to glucose in human body.

9. 2. Disaccharides Disaccharides - These are double sugars composed of two monosaccharide linked together with the removal of water molecule. The disaccharides which are of importance in the diet are sucrose , maltose and lactose . Their general formula is C12H22011

10. Cont… Sucrose:- Sucrose is the name given to sugar which we use daily. It is prepared from-sugar cane and sugar beet. It is made up of one unit of glucose and one unit of fructose. Lactose- It is the sugar present in milk. It is made up of one unit of glucose and one unit of galactose. It is the least sweet of all the sugars and is easily fermented to lactic acid and cheese. Maltose :- It is formed when whole grains are sprouted and in the commercial preparation of malt from starch. In the body, maltose is formed during digestion of starch. It is composed of two units of glucose.

11. 3. Oligosaccharides Oligosaccharides -They are composed of three to ten monosaccharide units linked to each other by the removal of water molecules. They are not as common in food as the mono, di and polysaccharides.

12. 4. Polysaccharides Polysaccharides - These are complex carbohydrate made up of 100 to 2000 glucose units linked to each other in a chain or branched form. Starches- They form approximately half the dietary carbohydrates which are consumed. They are present in abundance in cereals, pulses, tapioca, sago, roots and tubers.

13. Cont… Glycogen -This is also called animal starch as it is the form in which the animal body stores CARBOHYDRATES as a reserve source of energy. One third of the glycogen is stored in the liver and two-third is stored in muscles. Dextrin :This is formed in the first stage of starch breakdown either by enzyme during digestion or by the action of dry heat on starch during toasting a bread or browning flour.

14. Function of carbohydrates The chief function of carbohydrate is to provide energy to the body so that it can carry out day to day work and maintain body temperature. They are required for complete oxidaton of fat. Carbohydrates spare proteins from being broken down for energy and are used for body building and repair. Glucose in the only form of energy used by the CNS. The sugar lactose help in the absorption of the minerals calcium and phosphorus. Lactose also helps certain bacteria to grow in the intestine. Dietary fibers help in preventing constipation.

15. Sources

16. Daily requirements of carbohydrate Minimum of it should be 100 g daily and maximum 70% of total calories / day Majority of people in developing countries take it as high as 60-70 % while 40-50% in Europe and 30-40 % in U.S.A. The carbohydrate calories should be at least 40% in well-balanced diet. Again it depends upon the availability of fats and economic conditions of people, as fat is costly.

17. Digestion and absorption of carbohydrates Complex carbohydrates and sugars are too large to be absorbed through intestinal wall. Only monosaccharide can be absorbed into blood stream. The first stage in the digestion of carbohydrates takes place in the mouth when food is chewed. Ptyalin enzyme in the saliva acts on starch, splitting it into dextrin and maltose . As soon as the food reaches the stomach it mixes with the gastric juice . Lastly, its digestion is accomplished in the small intestines by pancreatic amylase and intestinal amylase, sucrose , lactase , maltase and iso -maltase present in the intestinal juice.

18. Metabolism of carbohydrates Glucose, galactose and fructose are absorbed in the intestines and pass to the liver through portal circulation. In the liver, a part of glucose and the entire galactose and fructose are converted into glycogen. A part of glucose passes into the general circulation, to the various tissues for being oxidized and used as energy. A small part of glucose is stored in the liver and muscles as glycogen and some portion of glucose is converted into fat and stored in adipose tissue .

19. Regulation of blood sugar 1. The fasting level of blood sugar in normal person is 80-100 mg per 100 ml. After consuming a meal, this glucose level steadily rises and may reach to 130-150 mg %. If the level exceeds 180 mg%, it is excreted in the urine and this condition is called diabetes mellitus. 2. A fasting blood sugar level above 140 mg% is called hyperglycaemia and below 70 mg% is hypoglycaemia . The hormone insulin secreted by the cells of the Islets of Langerhans in the pancreas helps in regulating the blood glucose level .

20. Deficiency of CHO A deficiency of carbohydrates in diet results in utilization of fat for energy and in severe deficiency, incomplete oxidation of fats causes ketone bodies to accumulate in the blood. It also results in PEM when it accompanies with protein deficiency.

21. Excessive carbohydrates Excessive consumption of refined sugars could be one of the causes of dental caries and tooth decay. Excessive sugar depresses the appetite, provides hollow calories and could result in malnutrition. High intake of sugar and refined carbohydrates increases the blood triglyceride level leading to heart diseases. Excessive carbohydrates are converted into fat and deposited in the adipose tissue, which could lead to obesity. Excessive fibres could irritate the intestinal lining causing cramps or bloating due to gas formation.

22. Question to be Ask ? Define cho ? Define cho , source of cho and function of cho ? Write a short note on digestion and absorption of cho ? Deficiencies and over consumption of cho ?