Carbohydrates

1. Carbohydrates • The carbohydrate family consists of the Simple carbohydrates (sugars) and the complex carbohydrates (starches and fibers). • Simple CHO: monosaccharides is single sugar molecule, and disaccharides are sugars composed of pairs of monosaccharides bonded together. “Lecture 3: Carbohydrates PowerPoint" by Dr. Michael Kobre, Achieving the Dream OER Degree Initiative, Tompkins Cortland Community College is licensed under CC BY 4.0

2. Carbohydrates • Carbohydrates (CHO) are made of carbon (C), oxygen (O), and. Hydrogen (H) atoms. Each of these atoms can form a specified number of chemical bonds. • Carbon: forms 4 bonds • Oxygen: forms 2 bonds • Hydrogen: forms 1 bond

3. The Chemist’s View of Carbohydrates • Carbohydrates are made of carbon, hydrogen and oxygen atoms. • These atoms form chemical bonds that follow the laws of physical chemistry. "DL-Glucose.svg" by NEUROtiker is licensed under CC BY 4.0

4. The Simple Carbohydrates • Monosaccharrides are single sugars (most are hexoses). • Glucose serves as the essential energy source for the body and is commonly known as blood sugar or dextrose. • Fructose is the sweetest momsaccharride, it occurs naturally in honey and fruits, and is added to many foods in the form of high-fructose corn syrup. • Galactose rarely occurs naturally as a single sugar it is found in mammalian milk bonded to glucose.

5. Carbohydrates • Glucose: serves as an essential energy source for all the body’s activities. Its significance to nutrition is tremendous. Glucose is one of the two sugars in every disaccharide and is the unit from which the polysaccharides (starch) are made from almost exclusively.

6. Carbohydrates "Five Important Monosaccharides-01.jpg" by OpenStax College is licensed under CC BY 4.0

7. Carbohydrates • Fructose: is the sweetest of the simple sugars. It has the same chemical formula as glucose, but a slightly different structure. Fructose occurs naturally in fruits and in honey. Other products include soft drinks, ready-to-eat cereals, and desserts that have been sweetened with high-fructose containing corn syrup.

8. Carbohydrates • Galactose: seldom occurs free in nature, galactose binds with glucose to form the sugar in mammalian milk. Galactose has the same numbers and kinds of atoms as glucose and fructose in yet another slightly different structural arrangement.

9. Simple CHO- Disaccharides • Disaccharides are pairs of monosaccharides bonded together one of which is always glucose. • Chemical reactions bond single sugars together. • Condensation reactions link monosaccharides together. • Hydrolysis reactions split molecules and commonly occur during digestion. • Maltose consists of two glucose units. Maltose is made during the germination of seeds and fermentation. • Sucrose is fructose and glucose combined. It is refined from sugarcane and sugar beets, tastes sweet, and is readily available in many food products. • Lactose is galactose and glucose bonded together. It is found in milk and milk products.

10. Simple CHO- Disaccharide Bonding "Figure 03 02 04.jpg" by CNX OpenStax is licensed under CC BY 4.0

11. Complex Carbohydrates • Complex carbohydrates contain many glucose sugars and in some cases, a few other mono-saccharides bonded together in structures called polysaccharides. • Three polysaccharides that are important in human nutrition are: • Glycogen (found in animals and humans) • Starches (found in plants) • Fibers (a structural component of plants)

12. Complex Carbohydrates "Three Important Polysaccharides-01.jpg" by OpenStax College is licensed under CC BY 4.0

13. Complex Carbohydrates • Glycogen: an animal polysaccharide composed of glucose synthesized by and stored in the liver and muscles as a storage form of glucose used for energy by the body. • Glycogen is not a significant food source of carbohydrate we consume and is not counted as one of the complex carbohydrates in food. It is made in our body by our liver from consumed CHO.

14. Complex Carbohydrates • Starches: just as the human body stores glucose as glycogen for energy, plants store glucose as starch for their fuel Starches are long, branched or un-branched chains of hundreds or thousands of glucose molecules linked together. These large bulky molecules are found in foods such as grains, rice, tubers (potatoes), and legumes (peas, beans).

15. The Complex Carbohydrates • Dietary fiber we eat comes from the fiber used for structure in plants. Fiber is very diverse, and cannot be broken down by human enzymes, we never digest the fiber we eat, it passes through our GI tract and never gets absorbed. Two types of fiber consumed are: • Soluble fibers are viscous and can be digested by intestinal bacteria (this property is also known as fermentability). These fibers are found in fruits and vegetables. • Insoluble fibers are nonviscous and are not digested by intestinal bacteria. These fibers are found in grains and vegetables.

16. The Complex Carbohydrates • Fiber Sources: • Dietary fibers are found in plant foods. • Functional fibers are health-benefiting fibers that are often added to foods or supplements we consume to increase our fiber intake. • Total fiber considers both dietary and functional fibers. • Although we do not digest dietary fiber, it has many health benefits for the human body and GI tract health.

17. Digestion and Absorption of CHO • The ultimate goal of digestion and absorption of sugars and starches is to dismantle them into small molecules, mainly glucose, that the body can absorb and use to supply our body with energy, structure and for regulation. The initial break down or CHO starts in the mouth and continues though the small intestine.

18. Digestion and Absorption of CHO • In the mouth: chewing of high-fiber foods slows the processing of foods containing starch, and the enzyme salivary amylase in saliva starts hydrolyzing starch to shorter chain starches and to disaccharides.

19. Digestion and Absorption of CHO • In the stomach: the swallowed food mixes with the stomach’s acid and protein digesting enzymes. These all inactivate salivary amylase whichs stops CHO digestion. The fibers also slow gastric emptying, creating a feeling of fullness (satiety) because of slowed gastric emptying.

20. Digestion and Absorption of CHO • The Small intestine: performs most of the processing of CHO digestion. A major CHO-digesting enzyme Pancreatic amylase enters the small intestine through the pancreatic duct and continues to break down polysaccharides into shorter chains and disaccharides. The final hydrolysis takes place at the outer membranes of the intestinal cells where specific enzymes finish the digestion process.

21. Digestion and Absorption of CHO "Major digestive enzymes.png" by Stephaniegreenwood is licensed under CC BY 4.0

22. Digestion and Absorption of CHO • At the small intestinal cell membrane, the following enzymes break down specific disaccharides: • Maltase: hydrolyzes maltose into 2 glucose molecules. • Sucrase: hydrolyzes sucrose into 1 glucose and 1 fructose molecule. • Lactase: hydrolyzes lactose into 1 glucose and 1 galactose molecule.

23. Digestion and Absorption of CHO • All disaccharides being broken down contribute at least 1 glucose molecule to the body. Fructose and galactose monosaccharide molecules must be converted by the liver into glucose molecules through chemical reactions.

24. Digestion and Absorption of CHO • In the large intestine: A few hours after a meal, usually only a small percent of the sugars and starches and all indigestible fibers remain in the GI tract. The carbohydrate not digested in the small intestine is known as resistant starch. Resistant starch can be found in whole beans, raw potatoes, and in some unripe fruits.

25. Digestion and Absorption of CHO • These resistant fibers and starches attract water, help to soften stools and increase the production of mucus in the large intestine. Flora (bacteria) in the large intestine can ferment resistant CHO. As bacteria use resistant CHO for fuel, they generates water, gas, and short-chain fatty acids. The fatty acids are absorbed in the large intestine and provide some energy for intestinal cells.

26. Transporting CHO into the Blood • Glucose can be absorbed to a small extent through the lining of the mouth. Most CHO nutrient absorption takes place in the small intestine. As blood from the intestines circulates to the liver monosaccharide molecules are transported to the liver for processing.

27. Lactose Intolerance • Some people develop or are born with a condition that leads to the inability to digest the milk disaccharide lactose. Symtoms include: bloating, gas, abdominal discomfort, and diarrhea. • The lactase enzyme (needed to digest milk sugar) activity may decline with age. Intolerance may also develop when the small intestinal cells are damaged by disease, certain medicines, or malnutrition. Humans can also be born with a lactase deficiency (a genetic condition).

28. Lactose Intolerance • Some people may have a limited dairy intake due to lactose intolerance. To help ensure they don’t develop deficiencies, they should secure other sources of riboflavin, Vitamin D, and calcium which are often consumed in milk and milk products.

29. Carbohydrate In The Body • The primary role of the available carbohydrates in human nutrition is to supply our body’s cells with energy. Glucose is the main energy providing fuel in human metabolism.

30. Glucose In The Body • Storing carbohydrates as Glycogen: The liver stores around 1/3 of the body’s total glycogen as a reserve fuel (~1400 Kcals) and can release it into blood as glucose to fuel the body when needed. • During glucose ingestion, our blood glucose rises and the liver can convert excess glucose to glycogen molecules which are stored in the liver.

31. Glucose In The Body • If our blood glucose levels fall, the liver can dismantle the stored glycogen back into glucose molecules and release them back into the bloodstream for use by the body’s organs including the brain, and central nervous system. • Muscle in the body also stores glucose as glycogen, however muscle glycogen is used by the muscle tissue only and is not released to other organs in the body.

32. Glucose In The Body • Under high levels of exercise, the body can use up it’s stores of carbohydrate in a few hours. Once carbohydrate stores are depleted or body's cells must seek out alternative sources of glucose. The brain, and developing red blood cells rely almost exclusively on glucose as a main fuel source.

33. Glucose In The Body • Making glucose from body protein: Body protein can be converted to glucose to some extent during times of starvation. Protein has many important functions in the body so it is usually not used to provide energy in the body. Body fat cannot be converted to glucose to any significant extent. When CHO stores are depleted, body proteins are cannibalized to make glucose to power the brain and blood cell production.

34. Glucose In The Body • Converting glucose to fat: When we eat more carbohydrates then we need to use, the body fills glycogen stores to full capacity in the liver and muscle. Once those stores are full, the body will store any extra consumed carbohydrate by having the liver convert glucose to fat and then store the fat in our adipose (fat) cells.

35. Converting glucose to fat • Unlike the liver cells which can only store about a half a day’s worth of carbohydrate energy as glycogen, adipose cells I the body can store unlimited quantities of fat.

36. Glucose Homeostasis • To function normally, the body has to maintain blood glucose levels that allow the cells to function normally. • If blood glucose levels fall below normal levels, a person may become weak and light-headed. If blood glucose levels rise above normal the person may feel tired. Untreated, high or low fluctuations of blood glucose can become fatal.

37. Glucose Homeostasis • Blood glucose levels are primarily regulated by two hormones made in the pancreas. • Insulin: which moves glucose from the bloodstream into cells of tissue (decreases blood glucose levels). • Glucagon: which brings glucose out of storage from the liver when needed (increases blood glucose levels). • Epinephrine: from the adrenal gland also releases glucose from liver stores during times of stress (e.g. an adrenaline rush).

38. Glucose Homeostasis "The Homostatic Regulation of Blood Glucose Levels.jpg" by OpenStax College is licensed under CC BY 4.0

39. Balancing Within The Normal Range • The maintenance of normal blood glucose levels ordinarily depends on one of to processes. When blood glucose levels fall too low, we can consume food to replenish it, or in the absence of food, the hormone glucagon can signal the liver to break down glycogen stores and move glucose into the bloodstream. • Eating balanced meals throughout the day helps the body maintain normal glucose levels.

40. Falling Outside The Normal Range • Foods normally do not blood glucose levels, homeostasis in the body does. • In some people blood glucose regulation falters. When this happens, either of two conditions result: diabetes (high levels) or hypoglycemia (low glucose levels). People with these conditions often have to plan their carbohydrate intake to help maintain their blood glucose levels within a normal range.

41. Diabetes • With diabetes, blood glucose levels remain high after eating a meal because insulin is either inadequate or ineffective, or not being produced in the body. • There are two main types of diabetes: • Type 1: Which the beta cells in the pancreas fail to make insulin. Causes can be genetics, toxins, a virus, and sometimes an autoimmune disorder.

42. Diabetes • Type 2 diabetes: Is the more common type. The body’s cell receptors that work with insulin fail to respond to insulin. This condition often occurs as a result of obesity and poor nutrition intake. healthy body weight, a balanced diet and maintaining physical activity are the best preventive measures against developing type 2 diabetes.

43. Hypoglycemia • In most healthy people, blood glucose levels rise after eating and then gradually fall back within normal range. People with hypoglycemia have blood glucose levels that drop dramatically, producing symptoms similar to an anxiety attack. Symptoms often include: weakness, rapid heartbeat, sweating, anxiety, hunger, and trembling and dizziness.

44. Hypoglycemia • Often, hypoglycemia can occur as a result of poorly managed diabetes. Sometimes taking too much insulin, strenuous physical activity, inadequate food intake or illness can cause drops in blood glucose levels. • In healthy people hypoglycemia is not common. People who have trouble with hypoglycemia need to eat a consistent amount of CHO throughout their day.

45. The Glycemic Effect Of Foods • Refers to how foods consumed effect blood glucose levels : different types of foods can effect how quickly glucose is absorbed after eating and can effect how high blood glucose rises, and how long it will take to return to the normal range. • Glycemic index: is a measurement used to classify foods according to their potential for raising blood glucose. • Low glycemic index foods: have slow absorption, rate and rise in blood glucose levels, and have a smooth return to normal blood glucose levels.

46. The Glycemic Effect Of Foods • High Glycemic index foods: When consumed cause a fast absorption, a higher surge in blood glucose levels and usually an over reaction in returning to normal that plunges glucose below normal levels which is very undesirable and can cause hypoglycemic symptoms . High glycemic foods are a poor choice for folks having difficulty controlling blood glucose levels.

47. The Glycemic Effect Of Foods • High-Glycemic Foods: • Sugar. • Flour. • Rice. • White potatoes. • Some fruits: bananas, grapes, cherries, watermelon. • Raisins. • Many breakfast cereals, including puffed rice and corn flakes. • Bread.

48. Health Effects and Recommended Intakes of Sugars • Sugar poses no major health problem except tooth decay. • Excessive intake of sugar may displace nutrients and contribute to obesity. • Consuming foods with added sugars should be limited. • Naturally occurring sugars from fruits, vegetables and milk are better sources.

49. Health Effects Of Sugars • Empty-kcalorie foods such as cakes, soda, and candies deliver energy from glucose with little or no other nutrient value. • By comparison, foods such as whole grains, vegetables, legumes and fruits contain some natural sugars and lots of starches and fiber deliver their glucose energy along with protein, vitamins, and minerals.

50. Accusations Against Sugars • Sugar causes obesity: foods high in sugar are usually high in fat. The notion that eating sweet foods stimulates appetite and promotes overeating has not been supported by research. • Sugar causes heart disease: researchers agree that unusually high doses of refined sugar can alter blood lipids to favor heart disease, however, total fats, saturated fats, cholesterol, and obesity have stronger influences on heart disease.