Nutrition Lec2 PDF

2 classifications of nutrients PREPARED BY FATIMAH FADHIL JAWAD PHD  Six classifications of nutrients ❑ Carbohydrates ❑ Fats ❑ Proteins ❑ Vitamins ❑ Minerals ❑ Water Defi...

2 classifications of nutrients PREPARED BY FATIMAH FADHIL JAWAD PHD  Six classifications of nutrients ❑ Carbohydrates ❑ Fats ❑ Proteins ❑ Vitamins ❑ Minerals ❑ Water Definition of a Calorie: A unit of measure for energy in food. Nutrients that have Calories: ✓ Proteins ✓ Carbohydrates ✓ Fats A food Calorie is actually a kilocalorie, which is equal to 1000 calories. Calorie is useful in comparing the energy available from different foods when we are deciding what food to eat. For example, a small apple contains only 80 Calories, while a slice of apple pie contains almost 350 Calories.  Carbohydrates, fats, and proteins provide energy and perform other important functions. We need energy for all activities. When our body uses carbohydrates, fats, and proteins, energy is released: calories. Calories per gram: Protein 1 Gram = 4 calories Carbohydrates 1 Gram = 4 calories Fat 1 Gram = 9 calories  Variables which affect nutrient needs: 1. Age 2. Gender 3. Activity Level 4. Climate 5. Health 6. State of nutrition  1-Carbohydrates Large quantities of carbohydrates are found in diets all over the world for the following reasons: 1. Carbohydrates are widely available low cost, and excellent storage capabilities for relatively long periods without spoilage and easily grown (e.g., grains, legumes, vegetables, fruits). 3. Carbohydrate structures vary from simple to complex providing both quick and extended energy for the body. 4. Dietary fiber, which is an indigestible carbohydrate, serves separately as a regulatory agent within the gastrointestinal tract.  Simple Carbohydrates Simple carbohydrates are the different forms of sugar, which are easy for the body to process. Classes of Simple Carbohydrates are classified into the followings: 1. Monosaccharides are the simplest form of carbohydrates. have one sugar unit, They are sweet, require no digestion, and can be absorbed directly into the bloodstream from the small intestine. They include glucose, fructose, and galactose. Glucose: also called dextrose, is the form of carbohydrate to which all other forms are converted for eventual metabolism. It is found naturally in corn syrup and some fruits and vegetables. The central nervous system, the red blood cells, and the brain use only glucose as fuel; therefore, a continuous source is needed. After energy needs are meet , excess glucose can be converted to glycogen, used to make nonessential amino acids and specific compounds (ribose, keratin sulfate, and hyaluronic acid) , or converted to fat and stored. Fructose: is primarily found in fruits (from which it gets its name) and in honey. The amount of fructose found in fruits depends on the degree of ripeness. Galactose: Galactose is not usually found as a free monosaccharide in the diet; rather, it is a product of lactose (milk sugar) by hydrolysis during the digestive process. Some infants are born with an inability to metabolize galactose, a condition called galactosemia. galactosemia is caused by the absence of an enzyme galactose-1 phosphate uridyl transferase (GALT)which is needed in the liver for the conversion of galactose to glucose. in the absence of this enzyme , galactose will be accumulation in the blood and tissues both galactose and fructose are metabolized in the liver by incorporation into metabolic pathways for glucose. 2. Disaccharides have two sugar units Disaccharides are simple double sugars that are composed of two single-sugar units linked together. The three disaccharides that are important in human nutrition are sucrose, lactose, and maltose. Sucrose = Glucose + Fructose Lactose = Glucose + Galactose Maltose = Glucose + Glucose Sucrose is common table sugar. Its two single-sugar units are glucose and fructose Sucrose is common table sugar. Its two single-sugar units are glucose and fructose. Sucrose is used in the form of granulated, powdered, or brown sugar, and it is made from sugar cane or sugar beets. Lactose is the sugar found in milk. It is distinct from most other sugars because it is not found in plants. It helps the body absorb calcium. Lactose is less sweet than monosaccharides or other disaccharides. Many adults are unable to digest lactose and suffer from bloating, abdominal cramps, and diarrhea after drinking milk or consuming a milk-based food such as processed cheese. This reaction is called lactose intolerance. It is caused by insufficient lactase , the enzyme required for digestion of lactose. There are special low-lactose milk products that can be used instead of regular milk. Maltose is a disaccharide that is an intermediary product in the hydrolysis of starch. It is produced by enzyme action during the digestion of starch in the body. It can be found in some infant formulas, malt beverage products, and beer. It is considerably less sweet than glucose or sucrose. Synthetically derived maltose is used as a sweetener in various processed foods  Complex Carbohydrates 3. Polysaccharides have many sugar units. Polysaccharides are complex carbohydrates that are composed of many single-sugar units. The important polysaccharides in nutrition include starch, glycogen, and dietary fiber Starches are complex carbohydrates that are made up of many units of glucose or other sugars, which form long chains. These chains must be broken down by the body into single units of glucose before they can be used. Starches take longer than sugars to be broken down into glucose. Starches provide energy to the body over longer periods than do simple sugars. Breads, cereals, pasta, and potatoes contain starch. Glycogen 1. is sometimes called animal starch. It's a crucial to the body’s metabolism and energy balance.Glycogen is stored in the liver and muscles, where it is constantly recycled (i.e., broken down to form glucose for immediate energy needs and synthesized for storage). The hormone glucagon helps the liver convert glycogen to glucose as needed for energy. 2. These small stores of glycogen help to sustain normal blood glucose during short-term fasting periods (e.g., sleep), and they provide immediate fuel for muscle action  Complex Carbohydrates Dietary Fiber is another complex carbohydrate, which comes from non- digestible part of plants. There are two types of dietary fiber: soluble and insoluble. Soluble fiber combines with waste and other substances to assist in their removal from the body. (Found in: oat bran, beans, apples, carrots, and other vegetables). Insoluble fiber absorbs water and helps to provide needed bulk to the diet. (Found in: whole grains and the skins and seeds of fruits and vegetables). Regulation of Protein and Fat by Carbohydrates 1. Carbohydrates help to regulate both protein and fat metabolism. 2. If dietary carbohydrate is sufficient to meet general body energy needs, protein does not have to be broken down to supply energy. 3. Likewise, with sufficient carbohydrate for energy, fat is not needed to supply large amounts of energy Central Nervous System 1. Constant carbohydrate intake and reserves are necessary for the proper functioning of the central nervous system 2. The master center of the central nervous system, the brain, has no stored supply of glucose; therefore, it is especially dependent on a minute-to-minute supply of glucose from the blood 3. Sustained and profound shock from low blood sugar may cause brain damage and can result in coma or death