Food and nutrition.pdf

Function of Food 93diets may be an important factor in the prevention of certain diseaseswhich appear to be much more prevalent in people consuming the lowfibrediets common in industrialized countries. Because it facilitates therapid passage of materials through the intestine, fibre may be a factor inthe control of diverticulitis, appendicitis, haemorrhoids and also possiblyarteriosclerosis, which leads to coronary heart disease and some cancers.Frequent consumption of any sticky fermentable carbohydrates, eitherstarch or sugar, can contribute to dental caries, particularly when coupledwith poor oral hygiene. Adequate intake of fluoride and/or a topicalapplication is the best protection against caries .FatsIn many developing countries dietary fats make up a smaller part oftotal energy intake (often only 8 or 10 per cent) than carbohydrates. Inmost industrialized countries the proportion of fat intake is much higher.In the United States, for example, an average of 36 per cent of total energyis derived from fat.Fats, like carbohydrates, contain carbon, hydrogen and oxygen. Theyare insoluble in water but soluble in such chemical solvents as ether,chloroform and benzene. The term "fat" is used here to include all fatsand oils that are edible and occur in human diets, ranging from those thatare solid at cool room temperatures, such as butter, to those that are liquidat similar temperatures, such as groundnut or cottonseed oils. (In someterminologies the word "oil" is used to refer to those materials that areliquid at room temperature, while those that are solid are called fats.)Fats (also referred to as lipids) in the body are divided into twogroups: storage fat and structural fat. Storage fat provides a reservestorehouse of fuel for the body, while the structural fats are part of theessential structure of the cells, occurring in cell membranes, mitochondriaand intracellular organelles.Cholesterol is a lipid present in all cell membranes. It has an importantrole in fat transport and is the precursor from which bile salts and adrenaland sex hormones are made.Dietary fats consist mainly of triglycerides, which can be split intoglycerol and chains of carbon, hydrogen and oxygen called fatty acids.This action, the digestion or breakdown of fats, is achieved in the humanintestine by enzymes known as lipases, which are present primarily inthe pancreatic and intestinal secretions. Bile salts from the liver emulsifythe fatty acids to make them more soluble in water and hence more easilyabsorbed.The many fatty acids in human diets are divided into two maingroups: saturated and unsaturated. The latter group includes both