All rights reserved. This book or any portion thereof may not be reproduced or used in any manner whatsoever without the express written permission of the publisher except for the use of brief quotations in a book review.
• Digestion, Absorption and Storage: Digestion of cooked starches begins in the mouth. There is only a little digestion that occurs in the stomach. Ptyalin (salivary amylase) and pancreatic amylase are digestive enzymes that break down carbohydrates. Carbohydrate digestion is completed in the small intestine. Glucose is transported through the cell membrane and is augmented by insulin. Metabolism is controlled by the rate which insulin is available. Carbohydrates are used completely, leaving no waste for the kidneys to excrete. Carbohydrates are stored either as Glycogen or Fat. Most are stored in the liver and skeletal muscles, but all body cells are capable of storing glycogen. Glucose that cannot be stored as glycogen is converted to fat. • Signs of Deficiency: Mild deficiency can result in weight loss and fatigue. Serious deficiency can result in ketosis. Fats The daily requirements of fats should not exceed 25% to 30% of an individual’s caloric intake per day. Lipids are greasy and insoluble in water; they are soluble in alcohol or ether. Chemical digestion of fats begins in the stomach, mainly in the small intestines by bile, pancreatic lipase and enteric lipase. The end products are glycerol, fatty acids, and cholesterol. Fatty acids are carbon chains and hydrogen; they are the basic structural units of most lipids. Fatty acids are either saturated fatty acids, unsaturated fatty acids, monounsaturated fatty acids or polyunsaturated fatty acids. • Classification and Sources: Fats are found in animals (lard, butter, milk, cream, egg yolks, and fat in meat, poultry, and fish) and plants (oils from corn, safflower, peanut, palm, as well as nuts and avocado). Glycerides are simple lipids. Triglycerides account for 90% of lipids in food and in the body. Cholesterol is a fatlike substance produced by the body and found in foods of animal origin. Cholesterol is a precursor of bile acids and is necessary for synthesis of steroid hormones. Lipoproteins are made up of various lipids and a protein. Phospholipids are lipoids, composed of glycerol, fatty acids, and phosphorus. • Functions: Fats provide a concentrated source of energy. They assist in the absorption of fat soluble vitamins like A, D, E and K. They are a major component of cell membranes and myelin sheaths. Fats improve flavor of foods and delay the stomach’s emptying time. Fats protect and hold organs in place. They also insulate the body, thus assisting in temperaturemaintenance. • Digestion, Absorption and Storage: There is no chemical breakdown of fats that occurs in the mouth and very little in the stomach. Digestion occurs in small intestine. Fats not immediately needed by the body are stored in adiposetissue. • Signs of Deficiency and Excess: Deficiency occurs when fats provide less than 10% of daily kcal requirement. Gross deficiency may result in eczema, retarded growth and weight loss. Excess fat consumption can lead to obesity and heart disease.