Chapter 4 Carbohydrates Sugar Starches and Fiber Carbohydrate

Chapter 4 Carbohydrates: Sugar, Starches and Fiber

Carbohydrate n n The primary role of carbohydrates is to provide the body with energy (calories). Why other alternative calorie sources not? q q Carbohydrates are the preferred fuel for the brain and nervous system. Carbohydrates are the ideal fuel compared to other alternatives: n n Less expensive than protein. High-fat diets are associated with chronic disease. © 2007 Thomson - Wadsworth

Carbohydrate Basics n Carbohydrate-rich foods are obtained almost exclusively from plants. q Milk is the only animal-derived food that contains significant carbohydrate. © 2007 Thomson - Wadsworth

Carbohydrates n n n n “A staple food is a food that can be stored for use throughout the year and forms the basis of a traditional diet” (Wikipedia). Staple foods are different from place to place Inexpensive starchy foods High energy (Calories) and mainly source of energy As part of every meal Name may be used synonymously with "food“ Main source of energy and have a primary place in diet

Complex Carbohydrates n Staple grain: a grain used frequently or daily in the diet. Examples include: q q Corn in Mexico Rice in Asia Wheat in Canada, Europe and USA Millet, rye, barley, and oats © 2007 Thomson - Wadsworth

Complex Carbohydrates n Refined: refers to the process by which the coarse parts of food products are removed. q For example, the refining of wheat into flour involves removing three of the four parts of the kernel —the chaff, the bran, and the germ—leaving only the endosperm. © 2007 Thomson - Wadsworth

Carbohydrates in Our Diet n n Carbohydrates make up most of the energy in a healthy diet. Grains are sources of carbohydrates. Refined carbohydrates lack fiber and many rich nutrients. Unrefined carbohydrates are healthier to eat.

Unrefined and Refined Foods

Whole Grains Whole grains are made up of n bran: containing fiber and vitamins n germ: mainly protein and vitamins n endosperm: starch, protein, vitamins, and minerals

The Wheat Kernel: A Whole Grain n Germ: the nutrient-rich and fatdense inner part of a whole grain. n Endosperm: provides energy; contains starch grains embedded in a protein matrix. n Bran: the fibrous protective covering of a whole grain and source of fiber, B vitamins, and trace minerals. n Husk: (chaff) the outer, inedible covering of a grain. © 2007 Thomson - Wadsworth

Complex Carbohydrates n Whole grain: refers to a grain that is milled in its entirety (all but the husk), not refined. q Whole grains include wheat, corn, rice, rye, oats, amaranth, barley, buckwheat, sorghum, and millet; two others—bulgur and cous— are processed from wheat grains. © 2007 Thomson - Wadsworth

Carbohydrates n Enriched: refers to a process by which the B vitamins thiamin, riboflavin, niacin, folic acid, and the mineral iron are added to refined grains and grain products at levels specified by law. n Fortified foods: foods to which nutrients have been added. Typically, commonly eaten foods are chosen fortification with added nutrients to help prevent a deficiency of a nutrient (iodized salt, milk with vitamin D) or to reduce the risk of chronic disease (juices with added calcium). © 2007 Thomson - Wadsworth

© 2007 Thomson - Wadsworth

Empty Calories Many processed/ready to eat foods contain added sugar that reduces nutrient density (empty calories)

Carbohydrates: n n n Group of components made up of one or more sugar unit Sugar unit: A sugar molecule that can not be broken down to yield sugar Sugar unite: contain Carbon, Hydrogen, Oxygen q The proportion of the hydrogen to oxygen is 2: 1 n H 2 O

Types of Carbohydrates: n n n Monosaccharide: A carbohydrate made up of a single sugar unit Disaccharide: A carbohydrate made up of two sugar units Polysaccharide: A carbohydrate made up of many sugar units linked together.

Types of Carbohydrates n n n Glucose, fructose and galactose are simple carbohydrates. Glucose is the blood sugar and found in cells. Sucrose is made up of a molecules of glucose and a molecule of fructose is a disaccharide. Maltose is made up of two glucose molecules. Lactose contains one glucose and one galactose.

Monosaccharides

Carbohydrate n Complex carbohydrates n n n Starch Fiber Glycogen (animal) Simple carbohydrates have one or two molecules of single sugars. n n Naturally occurring sugar(fresh fruits, vegetables, milk) Added sugars in concentrated form P. Aasassi/Fall 2009

Dissaccharides n Simple carbohydrates have one or two molecules of single sugars. q q maltose, sucrose and lactose are simple carbohydrates (two units) Glucose, galactose and fructose are single carbohydrates (two units) Glucose is the blood sugar and source of energy from carbohydrates (one unit) Galactose is milk sugar important in producing milk in lactating women and animals (one unit)

Dissaccharides

Complex Carbohydrates n n Complex carbohydrates contain many molecules of glucose. Starch, glycogen and cellulose are complex carbohydrates. q q Starch and glycogen are synthesized by a chain of glucose molecules joined by alpha 1– 4 and 1– 6 bonds they also have branched chain attached. Fiber (cellulose) is a chain of glucose molecules joined by beta 1– 4 bond that human intestine does not produce the enzyme to digest it.

Complex Carbohydrates n Glycogen: Storage form of glucose in human and other animals q n Liver and muscles Starch: Glucose molecules linked together n n q Straight Branched Storage form of carbohydrate in plants q q n Plant growth Plant reproduction Fiber: not digest by human, not absorbed

Complex Carbohydrates

Glucose is Produced by Plants through Photosynthesis

Chemistry of Carbohydrates n n n Starch is stored in the grains, stems and root of the plant. Fiber is found in the bran of the grains, stem, leaf, and other structures of the plants. There are two types of fiber in the plant varieties: q q Soluble fiber in fruits, oats and legumes Insoluble fiber mostly in grains and vegetables

Soluble and Insoluble Fiber Pectin Beans

Fiber n n Humans do not produce enzyme to digest fiber—therefore, no calories from fiber. Fiber provides many health benefits to humans: q Insoluble fiber: n n q provides bulk in the intestine to ease elimination. prevents constipation, diverticulitis, appendicitis, and may prevent colon cancer. Soluble fiber: n n combines with bile, eliminate it, preventing elevated blood cholesterol

Complex Carbohydrates n Soluble fiber q Around and inside plant cells q Dissolve in the water q Human enzymes can not digest q Broken down by bacteria in large intestine q Pectin, gums, mucilages, some hemicelluloses, and algal substances © 2007 Thomson - Wadsworth

Complex Carbohydrates n Insoluble fiber q q q Insoluble fibers do not dissolve in water Structural part of the plant (cell walls) Unchanged during the digestion n q q Adds bluk to fecal Wheat, broccoli and celery Cellulose, hemicellulose, and lignin.

Complex Carbohydrates Fiber and weight control: n Both type of fibers can help to control weight q Provides satiety (absorb water, delay the empting of stomach) q Prolongs eating time because of chewing of food q Eating fewer empty caloric foods P. Assassi/Fall 2009

Fiber in the Diet n n Fiber is important, but how much is appropriate? Harmful effect of too much fiber: q Decrease mineral absorption (especially iron, calcium and zinc). q Feeling of over-fullness and under-consumption of essential nutrients. q Dietary guidelines recommend 14 grams of fiber per 1000 calories. This amount is easily supplied by a diet rich in whole grains, fruits and vegetables (about 2040 grams daily) q The wholesale addition of purified fiber is not advised because it can be easily taken to extremes. q Variety of whole grain, legumes, nuts, fruits, and vegetables P. Assassi/Fall 2009

Carbohydrate Digestion & Absorption n n Mouth Small intestine q n Absorption through the small intestinal villi q q n n Digestive enzymes from pancreas Active absorption Passive diffusion Large intestine Elimination of undigested starch and fiber Modification of intestinal microflora Role of the pancreas

Carbohydrate Digestion & Absorption n Disaccharides and complex carbohydrates q Monosaccharide n Absorbed q Liver (blood)

Carbohydrate Digestion Mouth: n starch q first digestive enzyme to work q salivary glands (amylase), § breaking down starch to into the smaller polysaccharide and maltose

Carbohydrate Digestion n Stomach: q q q Stomach acid and enzymes Inactive salivary enzymes by acid No digestion

Carbohydrate Digestion n Small intestine q n Most of the digestion (break down to monosaccharide) Pancreas q enzymes and releases them through the pancreatic duct into the small intestine n Enzyme in the surfaces of the small intestine cells (brush border) break disaccharides into monosaccharide and the cell absorb them

Carbohydrate Digestion n Large intestine: q Fiber and other indigestible carbohydrates n Short chain fatty acid and gas q n Fatty acid § source of the energy for the cells in the colon, regulating cellular proceeses Some excreted in the feces

Carbohydrate Digestion n Liver and muscles take up surplus glucose to build the polysaccharide glycogen q Muscles hold 2/3 of body’s total store ( use it during the exercise) q Liver stored 1/3 body’s glycogen When glycogen stores are full and cells’ energy needs are met, the liver then reorganizes these extra energy compounds into fat and it is stored in fatty tissues of the body. Fat cells can store unlimited quantities of fat.

Carbohydrate Digestion

Carbohydrate Digestion n Lactose intolerance: inability to digest lactose as a result of a lack of the necessary enzyme lactase. q Symptoms include nausea, abdominal pain, diarrhea, or excessive gas q 70 % of the world people q African Americans, Mediterranean, Native Americans, and Asian q Less common in people of northern European q People who are sick or malnourished (developed temporarily)

Carbohydrate Digestion n Lactose intolerance: q Enzyme lactase n Lack of the enzyme q Lactose n Large intestine q q q Gas Cramp and diarrhea Prevalence n 30 to 50 million of American (African American, Native Americans, n Asian American) Calcium deficiency q q Yoghurt and cheese Lactase tablets

Lower lactose food Ø Yogurt Ø Acidophilus milk Ø Lactose free products © 2007 Thomson - Wadsworth

Glycemic Index n n n Different carbohydrate containing foods are absorbed at different rate. Simple carbohydrates and potato starch are absorbed fast and make a large spike in the blood sugar (a high glycemic index) causing a high insulin response. Beans, legumes and some mixed foods are absorbed slower and have lower glycemic index.

Glycemic Index

Glycemic Index n n Glycemic index (GI): a scale that ranks carbohydratecontaining foods by how much they raise blood glucose levels compared to a reference food such as glucose or white bread. The glycemic load (GL) is a measure of the extent to which blood glucose is raised by a given amount of carbohydratecontaining food. Glycemic effect: the effect of food on a person’s blood glucose and insulin response – how fast and high the blood glucose raises and how quickly the body responds by normalizing. Time for leaving food from stomach, time for digestion and glucose absorbetion © 2007 Thomson - Wadsworth

Glycemic Index n Refined sugars and starches q q Leave the stomach quickly Digest and absorbed quickly

Carbohydrate Functions n n Getting glucose to the cells, role of insulin. Problems of glucose metabolism q q Type 1 diabetes, pancreases loss of insulin producing ability. Autoimmune problem Type 2 diabetes n q increased body fat cells causing resistance to insulin delivery of glucose to the cells Role of insulin in regulating blood glucose levels

Functions of Monosaccharide n n Absorbed monosaccharids enter liver where galactose and fructose are converted to glucose. Glucose enters the blood and circulates. Insulin helps glucose enter the cells for energy. Glucagon helps excess blood glucose return to liver and muscles to form storage and form q n glycogen Glucose also is a part of genetic DNA, RNA, ATP and other functional molecules in the body.

When a person eats, blood glucose rises. High blood glucose stimulates the pancreas to release insulin. Insulin serves as a key for entrance of blood glucose into cells. Liver and muscle cells store the glucose as glycogen. Excess glucose can also be stored as © 2007 Thomson - Wadsworth fat.

Later, when blood glucose is low, the pancreas releases glucagon, which serves as the key for the liver to break down stored glycogen into glucose and release it into the blood to raise blood glucose levels © 2007 Thomson - Wadsworth

How the Body Handles Carbohydrates n Insulin: a hormone secreted by the pancreas in response to high blood glucose levels; it assists cells in drawing glucose from the blood. n Glucagon (glue-cuh-gon): a hormone released by the pancreas that signals the liver to release glucose into the bloodstream. © 2007 Thomson - Wadsworth

Blood Glucose Regulation

Cellular Carbohydrate Metabolism n n In cells, glucose is metabolized to produce energy. There are two pathways for producing energy: q Anaerobic pathway (incomplete metabolism) with production of lactate. n q Happens in absence of oxygen. Resulting in lower energy production Aerobic pathway (complete metabolism) with end products of CO 2 and H 2 O. n Happens when oxygen is present. Produces lot more energy.

Cellular Respiration

Breakdown of Fat and Protein n In the absence of carbohydrates body breaks down protein to form glucose to feed the brain. q q About ½ of amino acids skeletons can produce glucose Other amino acids produce ketone n n acidic molecules that changes the p. H of body environment to acid. Body also breaks down the stored fat to provide energy for body needs q q q Fat breakdown in the absence of carbohydrates results in ketone production. Ketone bodies are harmful to the body and are excreted through the urine. Severe ketosis can occur with untreated diabetes and can cause coma and even death.

Ketone Formation

Carbohydrates and Health n Are carbohydrates good or bad for you? q What kind of carbohydrates are beneficial to health? n q Whole grains, complex carbohydrates foods are healthy carbohydrates. What kind are not healthy carbohydrates to consume? n Refined carbohydrates and food with added sugar are not healthy and may cause risk of chronic diseases.

Diabetes n Insulin response is slow or ineffective q n Hyperglycemia occurs when blood glucose levels rise too high, glucose fails to get into cells, and blood glucose stays too high for an abnormally long time. Type 2 diabetes is most common q little insulin, or cellular resistance to insulin. Type 1 diabetes is less common q q production of no or very little insulin requires insulin injections to control blood sugar levels incidence of type 2 diabetes is increasing in children and adolescents. Obesity is the major risk factor for diabetes P. Assassi/Fall 2009

Diabetes n Carbohydrates are generally blamed for diabetes. The interesting fact is again which kind of carbohydrates are to be blamed. q q Whole grain and complex carbohydrates prevent type 2 diabetes by preventing fat cells accumulation in the body. Refined carbohydrates increase empty calories in the diet may cause weight gain, increase resistance to insulin causing type 2 diabetes.

Diabetes n n Type 1 diabetes is due to lack of production of insulin from pancreas causing blood glucose to elevate. It can be controlled by a diet very low on fast absorbing starches (potato) and refined sugars. q q A diet high in fiber and whole grains help slow absorption and prevent fast rise in blood sugar. In sever cases insulin must be injected to regulate blood sugar levels.

Blood Glucose Levels in Diabetes

Diabetes n n n Incidences of diabetes in the US is on the rise. Certain racial groups are more susptible to diabetes than others. Lifestyle, dietary habits physical activity and environment also play a role. Managing diabetes with diet, exercise and medication. Symptoms and complications of diabetes.

Incidence of Diabetes

Other Health Problems n Hypoglycemia: q q n Dental caries: q q n Reactive hypoglycemia (high carbohydrate food) Fasting hypoglycemia Dental hygiene Refined sugars Carbohydrates and weight management: q Which kind to consume?

Carbohydrates and Weight Management

Carbohydrates & Body Weight n n Carbohydrates and weight management. Role of refined carbohydrates in storage of fat. Role of insulin in body fat accumulation. The consequence of low or no carbohydrate diets? q n n Ketosis and ketogenic diets Role of ketones in weight loss Benefits and harms of nonnutritive sweeteners.

Nonnutritive Sweeteners

Carbohydrates and Heart Disease § § Diets with high sugar, added sugar glucose or any simple sugar raise blood sugar, cholesterol and the risk of heart disease. High fiber containing diets with both soluble and insoluble fiber reduce the risk of heart disease.

Carbohydrates and Heart Disease n n n Consuming foods high in soluble fiber reduce cholesterol synthesis by liver. Soluble fiber in legumes, fruits, oats, brown rice, etc. bind with bile in the intestine, removing it from the body preventing bile reabsorption, and cholesterol re-synthesis. Soluble fiber may also reduce blood cholesterol by other means.

Cholesterol and Soluble Fiber

Carbohydrates and Heart Disease n Diets with high insoluble help reduce risk of heart disease by: q q q Reducing absorption of starch and sugars. Keeping blood glucose normal Reducing food intake by filling the stomach and reducing the appetite. Preventing obesity Reducing blood pressure. Preventing formation of diverticula

Diverticula

Intestinal Health and Fiber n Insoluble fiber is not digested, absorbs water in the intestine and increase in volume conferring benefits: q q Softens the stool, making elimination easy. Preventing constipation, diverticulitis, appendicitis, hemorrhoids, and possibly colon cancer. Speed up the movement of waste materials from the bowl. Modify the bowl micro flora environment positively.

Meeting Carbohydrate Needs n Carbohydrates intake is to meet the needs of: Adequate blood glucose levels to meet the brain, red blood cells and nerves energy requirements (about 300 grams/day). q Minimum carbohydrate intake to prevent ketosis is 100 grams/day q n Recommendations are: q n 45% – 65% of total daily calorie intake should come from complex carbohydrates. In the US diet, the right percentage of calories consumed from carbohydrates, but it is mostly refined or added sugars.

Healthy Carbohydrate Choices

Choosing Carbohydrates Wisely

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