Fats Unit 3rd of nutrition

Fats unit 3rd of nutrition for BSc Nursing and GNM ist Year

1. Unit 3 rd nutrition

2. Objective Define fats Classification of fat Daily recommend dose Sources Function Digestion, absorption and storage Metabolism Deficiencies of fats Over consumption

3. LIPIDS Fats and oils belong to a group of compounds called lipids . They are characterized by greasy feel, insolubility in water and solubility in some organic solvent. Like the carbohydrates, they are mainly made up of carbon, hydrogen and oxygen. They are more concentrated source of energy providing two and half times more energy than carbohydrates and proteins. Unlike carbohydrates lipids contain of oxygen and a larger proportion of hydrogen and carbon. Fats are solid at 20°C. They are called oils if they are liquid at that temperature.

4. Cont… Simple fats and oils are of great importance in food preparation. The quality of the food product depends largely on the fats and oils used for while preparing it. The most common form of food fats are triglyceride.

5. CLASSIFICATION OF LIPIDS A. On the Basis of Structure:- 1. Simple lipids. 2. Compound lipids. 3. Derived lipids. 4. Sterol.

6. Cont… Simple lipids :- They are made up of three fatty acids attached to glycerol. They are mixed triglycerides which means that more than one type of fatty acids are present in the fat, e.g. cooking oils and butter. Simple lipids constitute more than 98% of food and body fats. Compound lipids :- They are fats in which at least one fatty acid is replaced by carbohydrate, protein or phosphorus i.e. they are fats + non fat molecules, e.g. phospholipids , glycolipids and lipoprotein .

7. Cont … Derived lipids- They are the breakdown products of fats and include diglycerides, mono- glycerides , glycerol and fatty acids. Sterol: - They are not made up of fatty acids and glycerol but have benzene ring structure. These fat like substances include cholesterol and fat soluble vitamins A, D, E and K

8. B. Classification of lipids on the basis of fatty acids present 1. Saturated fatty acids 2. Unsaturated fatty acids : -Mono unsaturated fatty acids -Poly-unsaturated fatty acids 1. Saturated fatty acids :- In saturated fatty acids, each carbon atom in the fatty acid carries all the hydrogen atoms possible. They have single bonds between carbon atoms. Saturated fatty acids are found mainly in animal fats and plants too for example, coconut and palm oils although vegetable oils have an extremely high percentage of saturated fatty acids and they are solid.

9. Cont… 2. Unsaturated fatty acids:- The full complement of hydrogen atoms is not received in unsaturated fatty acids. This leads to the formation of double bond between the atoms so they have one or more double bonds between the carbon atoms. Unsaturated fatty acids are further divided into two- 1) Mono unsaturated fatty acids (MUFA) 2) Poly unsaturated fatty acids (PUFA)

10. Cont… 1) Mono unsaturated fatty acids (MUFA):- They have one or more double bonds between the carbon atoms. Oleic acid is an example of monosaturate fatty acid and it is found in ground nut oil, olive oil and corn oil. They are mostly found in vegetable oils. There is exception as, for example, fish oils contain mono and polyunsaturated fatty acids and it is liquid. 2) Poly unsaturated fatty acids :- Fatty acids with two or more double bounds. Examples are linoleic , linolenic and arachidonic .

11. Cont… Cholesterol: - It is fat like substance present in food. It is different in structure from triglycerides. It is present in all cells of the body, large amount in brain and nerve tissue. Large amount of cholesterol is also present in sebum secreted by the sebaceous glands . The blood of normal human being contains 150-200 mg / 100 ml blood. The human body gets cholesterol from two sources, one it is synthesized in the liver . It performs following functions :- 1) Cholesterol is a boding of all steroid hormones. 2) It is also a bond of vitamin D. 3) It is required for formation of bile. 4) It is an essential constituent of cell membranes. If it is consumed in excess , it leads to diseases of the cardiovascular system .

12. Cont… Visible and invisible fats :- Visible fats are those which are separated from their natural sources, e.g., ghee from milk, cooking oils from seeds and nuts. So it is easy to estimate their intake in daily diet. Invisible fats are those which are not visible to naked eyes. They are present in almost every article of food, e.g. cereals, pulses, nuts, milk, eggs, etc. It is difficult to estimate their intake. In fact the major contribution to total intake is from invisible sources.

13. Functions of fats :- 1) Energy - Fats are a concentrated source of energy. One gram of fat gives 9 kcal when it is oxidized in the body. All tissues except those of central nervous system and brain can utilize fat as a source of energy. Fats are deposited in the adipose tissue and this deposit serves as a reserve source of energy during starvation. 2) Thermal insulation - Subcutaneous fat acts as an insulator against cold by retaining body heat. 3) Protein sparing action :- An adequate intake of fat in the diet allows proteins to perform their main functions of growth and maintenance. In this way, fats spare proteins from being oxidized for energy. 4) Protection of vital organs :- Fat provides a protective padding to vital organs, Such as heart, kidney and intestine from mechanical shock and keeps them in place.

14. Cont… 5) Absorption of fat soluble vitamins- Fats are essential for the absorption of fat soluble vitamins A, D, E and K, especially carotenoids present in foods of vegetable origin. So fats serve as vehicles for fat soluble vitamins. 6 ) Essential fatty acids : Fats contain essential fatty acids, viz. linoleic , linolenic and arachidonic acids, which are essential for maintaining tissues in normal health. 7) Satiety value- Fats improve the palatability( svaadisht ) of the diet and give satiety value, i.e., a feeling of fullness in the stomach.

15. Cont… 8) Synthesis of hormones :- The cholesterol is necessary for the synthesis o- some steroid hormones and bile acids, e.g., sex hormone. 9) Precursors of prostaglandins :- Poly unsaturated fatty acids are precursors of prostaglandins - a group of compounds now recognised as "local hormones." They play a major role in controlling many of the physiological functions.

16. Sources of Fats Animal fats : The major sources of animal fats are ghee, butter, milk, cheese, egg, yolk, meat and fish. Animal fats are mostly saturated fats. Vegetable fats : Some plants store fat in their seeds, e.g. groundnut, mustard soybeans, sesame( tiil ), coconut, almond( badam ), cashew nut( kaju ), safflower and sunflower etc. Other sources -Small quantities of fat (invisible) are found in most other foods such as cereals, pulses and vegetables. Large cereal consumption in India provides considerable amounts of invisible fats.

17. Fat Requirement The WHO expert committee on prevention of Coronary Heart Disease (CHD) has recommended 20 to 30 percent of total dietary energy to be provided by the fats. At least 50 percent of fat intake should consist of vegetable oils rich in essential fatty acids. The Indian Council of Medical Research (ICMR) 1989 has recommended a daily intake of not more than 20 percent of total energy intake through fats. In developed countries dietary fats provide 30 to 40 percent of total energy.

18. Digestion and Absorption of Fats When a person takes his food it enters the stomach where gastric lipase produces slight hydrolysis of fat (process of splitting into smaller molecules by uniting with water). In the duodenum, bile secretion emulsifies fats. Pancreatic lipase and intestinal lipase break down the fats into a mixture of monoglyceride , diglycerides and fatty acids. The products of digestion pass through the lacteals of the small intestines to the thoracic duct, then to the blood stream and every cell of the body.

19. Fat Metabolism The liver assists in the oxidation of fats and prepares fats for deposition in the tissues. In the tissues, some of the fat is oxidized to give heat and energy. Some of the fat is stored in the fat deposits. Fats, before they can be used as body fuel, must be prepared for combustion in the tissues by the liver. This is a chemical process carried out by the liver cell is known as the desaturation of fats. The waste products which result from the combustion of fat in the carbon dioxide and water, excreted by the lungs, skin and kidneys.

20. Cont.. If the combustion is incomplete, the acetone bodies are formed and also leave the body by the same routes. The volatile acetone can be smelt in the "sweet breath" and acetone and diacetic acid can be found in the urine. Fat is a better fuel than glucose, in that it produces twice as much heat and energy per gram of fuel used. On the other hand, it is less easy to digest, absorb and less satisfactory to burn provided it is burnt with sufficient sugar.

21. Cont… If there is little or no sugar to burn with it, combustion is incomplete and ketone bodies are formed. When large amount of ketone bodies are formed, this condition is known as acidosis, which results in drowsiness, coma and finally death. Fat, which is not used as fuel, can be stored as fatty tissues and in the body cavities. It can be stored in large quantity causing obesity.

22. Effects of Deficiency A deficiency of fat may result in a deficiency of fat soluble vitamins which may affect the growth and weight of the children. Deficiency of essential fatty acids in the diet leads to a condition known as phrenoderma or toad skin.

23. Effects of Excessive Fats The greater concern today is the problems related to excessive intake of fats. It can pose a threat to human health. Excessive fat causes obesity as it is stored in the adipose tissues. In normal subjects, adipose tissues constitute between 10 to 15 percent of body weight but in fat people it may increase to 30 percent. Most of the body fat is in the form of triglycerides. Hypercholesterolemia and Coronary Heart Disease When the blood cholesterol level is over 250 mg per 100 ml, the incidence of atherosclerosis and Coronary heart disease is high

24. Question to be Ask ? Define fat and classify it ? Source and function of fat Deficiency and over use ? Short note on cholesterol ? Source of fat ?