Dietary fats

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Text of Dietary fats

  • 1.Dr Shailendra Meena PG StudentL N Medical College and J K Hospital Bhopal

2. Introduction Fats are best known members of a chemical groupcalled the lipids. The term lipid is applied to a group of naturally occurring substances characterized by their insolubility in water, greasy feel and solubility in organic solvents like ether, chloroform, benzene or other fat solvents. The term lipid was first used by the German biochemist Bloor in 1943 3. Introduction cont. In normal human subjects, fats constitutes between10-15 % of body weight. Most of the body fat(99%) is stored in the adipose tissues. Fat present in the diet or in human body are in the form of fatty acids, triglycerides, phospholipids and cholesterol. Each fat molecule is made up of four compounds, one alcohol and three fatty acids. 4. Functions of Fats 1) Insulation and Padding: Fats are deposited in adipose tissue, subcutaneous tissue and abdominal cavity Fats surrounds the organs and laced throughout muscle tissue Fats functions like insulating material against cold Fats protects vital organs against physical injuries by forming a padding around them 5. Functions of Fats cont 2. Energy: The primary function of fat is to supply energy. It is a very concentrated source of energy. Each gram of fat when oxidized yields approximately 9 kcal, twice as much energy as one gram of carbohydrate or protein. Fat specially supply energy in between the meals and during starvation. 6. Functions of Fats cont 3. Carriers of fat soluble vitamins: Dietary fat is a carrier of the fat soluble vitamins-A,D,E and Vitamin K Fat is also necessary for the absorption of Vitamin A and its precursor, carotene. 7. Functions of Fats cont 4. Satiety function: Fats improves the palatability of the diet. It slows digestion--resulting in satiety (a sense offullness and satisfaction after eating). In the absence of fats the food become non palatable. 8. Functions of Fats cont 5. Fats provide essential fatty acids which the body cant manufacture. 6. Fats are the constituents of cell membrane and regulates the membrane permeability. 7. Fats are also function as cellular metabolicregulators in the form of prostaglandins and steroid hormones. 9. Sources of dietary FATS Fats of animal origin : Ghee, butter, milk, cheese, eggs and fat of meat and fish Fats of plants origin: Groundnut oil, Coconut oil, Palm oil, Mustard oil, Canola oil, Sesame oil, Corn oil Other Sources: Cereals, Pulses, Oil seeds (Sunflower, Safflower, Soyabean, Cottonseeds), rice bran and Leafy green vegetables 10. Classification of Fats Mainly classified into two ways: A) Based on bio chemical composition B) Based on nutritional significance 11. Bio chemical classification of fats A. Simple Lipids:Simple lipids are defined as those which yield only one or more fatty acids and an alcohol on hydrolysis. Example: 1) Fats and Oils, also known as triglycerides 2) Waxes 12. Bio chemical classification of fats cont. B. Compound Lipids:Compounds lipids are those lipids which contain in addition to fatty acids and glycerol, some other organic compounds such as phosphoric acid, nitrogenous base, sugars and Proteins. Example: Phospholipids, Sphingolipids, Glycolipids, Sulpholipids and lipoproteins 13. Bio chemical classification of fats cont. C. Derived Lipids:These are the derivatives obtained on the hydrolysis of simple and compound lipids which possess the characteristics of lipids. Example: Fatty acids, mono and diacylglycerols, lipid soluble vitamins, steroid hormones and ketone bodies 14. Nutritional classification of Fats 15. Digestion of Fats Five different phases: Hydrolysis of triglycerides (TG) to free fatty acids (FFA) and monoacylglycerols Solubilization of FFA and monoacylglycerols by detergents (bile acids) and transportation from the intestinal lumen toward the cell surface Uptake of FFA and monoacylglycerols into the cell and resynthesis to triglyceride Packaging of TGs into chylomicrons Exocytosis of chylomicrons into lymph 16. Enzymes Involved in Digestion of Lipids lingual lipase: Hydrolyze short and medium chain fatty acids. Gastric Lipase: Hydrolyze Long, medium and short chain fatty acids. Pancreatic lipase: major enzyme affecting triglyceride hydrolysis Colipase: protein anchoring lipase to the lipid lipid esterase: secreted by pancreas, acts on cholestrol esters, activated by bile phospholipases: cleave phospholipids, activated by trypsin 17. Digestion of Fats cont. 18. Metabolism of Fats cont 19. Products of Fats Metabolism 1. 2. 3.4. 5.Fatty Acids Triglycerides Phospholipids Sterols Lipoproteins 20. 1.Fatty Acids Saturated Fatty AcidsUnsaturated Fatty Acids Monounsaturated Fatty Acids - Polyunsaturated Fatty Acids 21. Saturated fatty acidsSaturated fatty contains no double bonds (having no points of Unsaturation). 22. Saturated fatty acids continues.. Saturated fats are considered as harmful fats because they increases total cholesterol level and TGs level. Sources : Animal foods such as meat, poultry and full-fat dairy products Tropical oils such as palm and coconut RDA: Less than 10% of total energy intake per day. 23. Unsaturated fatty acidsFatty acid with one or more points of Unsaturation.Unsaturated fats are found in foods from both plant and animal sources. 24. Monounsaturated fatty acids Fatty acid containing one point of Unsaturation. They are considered as beneficial for human health. Replacing SFA with MUFA reduces LDL cholesterolconcentration and total cholesterol / HDL cholesterol ratio. Replacing carbohydrate with MUFAs increases HDL cholesterol concentration. Sources: vegetable oils such as olive, canola, and peanut. RDA: By difference 25. Classification of MUFAs Monounsaturated Fatty acids are of two type: 1) Cis- unsaturated fatty acids 2) Trans- unsaturated fatty acids 26. Cis- unsaturated fatty acids Natural unsaturated fatty acids have Cis- double bonds. The unsaturated fatty acids cant bunch tightly together. The bend helps the fat stay liquid rather than solid. Significance Decreases total cholesterol and TGs level. Increases HDL level. 27. Trans unsaturated fatty acids Unsaturated fatty acids (MUFAs and PUFAs) containing one or more double bonds in trans configuration are called trans fatty acids (TFAs). Hydrogen atoms are on the opposite sides of the molecule. 28. Trans fatty acids cont. Produced during partial hydrogenation of vegetable oils. Partially hydrogenation of vegetable oil results in longer shelf life of a product. less rancidity and oxidation when exposed to heat and light. Also developed in vegetable oils during frying and heating. Sources: Formation of trans fatty acids in edible oils during the frying and heating process (Vol.123, No.4, 15Dec.2010, pp 976-982, doi: 10.1016/j.foodchem.2010.05.048) 29. Why trans fatty acids are harmful Trans fatty acids are much more linear than cis fatty acids, so their melting points are higher and studies have shown that trans fats may act similarly to saturated fats. Increases the ratio of total cholesterol to HDL cholesterol, a powerful predictor of the risk of CHD A recent study suggests trans fats harm the cardiovascular system by triggering inflammation in blood vessels. In addition, trans fat may increase risk for cancers of the breast and prostate. 30. Trans fatty acids cont. Sources: 1. Spreads: Butter, margarine 2. Package foods: Cake mixes, Biscuits 3. Soups: Plain soups, Noodle soups 4. Fast foods: Deep fried Fish and Chicken, Pancakes 5. Frozen foods: Frozen pies, pot pies, wafers 6. Backed foods: Cakes, doughnuts 7. Chips and Crackers: Potato chips 8. Cookies and Candy: Choc0late bars, Cream filled cookies 31. RDA for Trans fatty acid The American Heart Association recommends limiting total trans fat intake to less than 1 percent of our total daily calories, which means less than 2 grams per day for many people. Since most of us get that much from naturally occurring trans fat in red meat and dairy, we need to cut trans fat from other foods to zero. That means checking every ingredient list and bypassing foods that declare any hydrogenated oils or partially hydrogenated oils, even if it states "trans fat 0 g" on the nutrition panel. 32. Polyunsaturated fatty acidsPolyunsaturated fatty acids are those fatty acids where Unsaturation occur more than two points.They possess protective role on human health. considered as beneficial for consumption. 33. Polyunsaturated fatty acids cont Increase esterification process of cholesterol & prevents itsabsorption. By increasing the synthesis of eicosanoids, acts as an antiplatelet aggregating factor, so decreases the chances of clot formation. Decreases the synthesis of the precursor of VLDL AND TGs. Increases clearance of LDL cholesterol. 34. Polyunsaturated fatty acids cont Sources: Found in nuts and vegetable oils such as safflower, sunflower, and soybean, and in fatty fish. RDA: 6-10% of total energy intake per day. 35. Essential Fatty Acids: There are two PUFAs which cannot be synthesized in the body and required in the preformed state in diet for growth and maintenance of normal skin. These are called Essential fatty acids and include linoleic acid and linolenic acid. The term essential fatty acid was introduced by Burr and Burr. 36. Essential Fatty Acids cont.. Sources of linoleic acid: Leafy vegetables, nuts, vegetable oils (seasame, corn oil,sunflower, soybean), poultry fat Sources o f linolenic acid: Nuts, seeds (soybean, walnuts, flaxseed) and oils(soybean, canola) RDA: Minimum intake levels for essential fatty acidsestimated to be 2.5% E LA and 0.5% E ALA 37. Omega 6 Fatty Acid- Linoleic acid RDA: 5-8% of total energy intake per day Sources: Safflower oil Sunflower oil Corn oil Soybean oil Pros: - helps lower LDL cholesterol; thereby lowering our risk of heart disease - helps make our blood "sticky" so it is able to clot - support skin health 38. Omega 6 Fatty Acid (continued) But when omega-6s aren'