Fat In The Diet example essay topic

LIPIDS AND NUTRITION Lipids can be defined as molecules, synthesized by biological systems, which have, as a major part of their structure, long aliphatic hydrocarbon chains that may be branched or unbranched, may form rings and may contain unsaturated linkages. Lipids have been matter of health concern in human beings. There are several reasons for it: vs. High prevalence of cardiovascular disease (CVD) and most of the lipid chemists have associated this with high consumption of fat especially saturated fatty acid (SFA) vs. Obesity vs. Thus the widespread desire to reduce fat in the diet has given rise to low and reduced fat products. vs. Nevertheless fats provide a concentrated source of energy and have their important place in the diet. vs. Lipids in human diet are derived from storage and structural lipids of plants and animals. vs. More than 90% of dietary lipids are originates from adipose tissue of animals and plant seed oils. Dietary fats may be divided into two types. Dietary fats Visible fats Invisible or hidden fats They are fats consumed as such They are fats present as e.g. butter, ghee, oils, etc. part of other food item e.g. fat incorporated in baked foods, pastries, etc The following table shows the percentage fat content of some foods.

TABLE - 1 Fat content of some foods Foods % Fat Cooking oils 100 Lard 99 Butter 82 Margarine 81 Peanuts, roasted 49 Cream 48 Cheese 34 Chocolate, milk 30 Beef, average 24 Cream, Single 21 Herring 14 Eggs 11 Chicken 4.3 Milk, Full cream 3.8 Milk, semi-skimmed 1.7 Cod 0.7 Ques: How much fat does a man need? Ans: Fats constitute approximately 34% of energy in the human diet. Fats are energy-rich and provide 9 Kcal of energy per gram. Health professionals say 22 kg / capita / year as against the present consumption of fats in our country - about 8.8 kg / capita / year. In industrialized nations, it is 26 Kg / capita / year. Nutritional contributions of various food lipids Lipids constitute a heterogeneous group of compounds of biochemical importance.

The following general classification of lipids in based on the chemical nature. Lipids 1) Simple LipidsTriacylglycerols (TAG) or triglycerides or neutral fats: -Esters of fatty acids with glycerol. Structure of TAG Function: - TAG are the storage form of lipids in the adipose tissue. The energy value of TAG to body is 38 KJ for one gram compared with about 17 KJ for proteins and 16 KJ for carbohydrates. 2) Waxes They are esters of fatty acid with high molecular weight alcohols, e. g., palmitate, the major component of beeswax.

It is an ester of palmitin acid with the alcohol, . OCH 3 (CH 2) 14 C O CH 2 (CH 2) 28 CH 3 Palmitin acid I- Function: - They are related to their water repellent properties and their firm consistency. Birds secrete waxes from their pre an glands to make the feathers water repellent. Compound lipids 1) Phospholipids They are composed of phosphoric acid, fatty acid and a nitrogenous base. They are derivatives of acid, a triglyceride modified to contain a phosphate group at the third position as shown in the following structure. If X = H Name of phospholipidPhosphatidic acid+X = CH.

CH 2 NH 3 Phosphatidylethanolamine Nature: Amphiphilic nature i. e., both hydrophobic (fatty acids) and hydrophilic portion (polar head group attached to 3rd carbon (C-3) are present in the molecule. Function: Due to its bipolar nature it forms 50% of bio membrane lipid bi layer. The hydrophilic head group face outward to intracellular media and inward to the cytoplasm, where fatty acid tails form hydrophobic interaction in membrane center and maintain bio membrane fluidity. 2) Sphingolipids They are composed of one molecule of long chain amino alcohol sphingosine as one of its derivatives, one molecule of long chain fatty acid, polar head group alcohol and sometimes phosphoric acid in die ster linkage at polar head group. Structure Functions: Sphingomylein makes up more than 25% of myl ein sheath, the lipid-rich structure that protect and insulate cells of central nervous system. 3) Lipoprotein: Blood lipid (Cholesterol triglycerides and phospholipid) are transported to blood bound proteins.

These complex particles are called lipoproteins which vary in size, density and composition. Lipoproteins are divided into five classes. a) Chylomicronsb) Very low density lipoproteins (VLDL) c) Inter mediate density lipoproteins (IDL) d) Low-density lipoprotein (LDL) e) High-density li proteins (HDL). TABLE-2 Characteristics and Functions of LiproteinsCharacteristics Class of Lipoproteins Chylo micron VLDL IDL LDL HDL Density g / ml OriginPhysiologicl roles Composition % TAG cholesterol Phospholipid Protein Major Apo lipo-protein.