Carbohydrates

1. Carbohydrates

2. 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 nature.

4. Types of CARBOHYDRATE • Simple • Monosaccharide's • Glucose • Fructose • Galactose • Disaccharides (Monosac + Glucose) • Maltose • Sucrose (Table sugar) • Lactose (Milk sugar)

5. The Simple Carbohydrates • Monosaccharrides are single sugars • Glucose serves as the essential energy source, and is commonly known as blood sugar or dextrose. • Fructose is the sweetest, 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.

7. The Simple Carbohydrates • Disaccharides are pairs of monosaccharides, one of which is always glucose • Maltose = glucose + glucose • Sucrose = glucose + fructose • Lactose = glucose + galactose

8. The Simple Carbohydrates Disaccharides • Maltose = two glucose units. It is produced during the germination of seeds and fermentation. • Sucrose is refined from sugarcane and sugar beets, tastes sweet, and is readily available. Called table sugar • Lactose is found in milk and milk products. Called milk sugar

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10. The Complex Carbohydrates • Few (oligosaccharides) or many (polysaccharides) glucose units bound/linked together in straight or branched chains.

11. Types of CARBOHYDRATE • Complex = Polysaccharides • Starch • Fiber • Glycogen

12. The Complex Carbohydrates • Starches • Storage form of glucose in plants • Found in grains, tubers, and legumes • Glycogen • Storage form of glucose in the body • Provides a rapid release of energy when needed

13. Glycogen Starch (amylopectin) Starch (amylose) A glycogen molecule contains hundreds of glucose units in highly branched chains. Each new glycogen molecule needs a special protein for the attachment of the first glucose (shown here in red). A starch molecule contains hundreds of glucose molecules in either occasionally branched chains (amylopectin) or unbranched chains (amylose). Stepped Art Fig. 4-8, p. 106

14. The Complex Carbohydrates • Dietary fibers provide structure in plants, are very diverse, and cannot be broken down by human enzymes. • 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, oats, barley, legumes. • Insoluble fibers are nonviscous and are not digested by intestinal bacteria. These fibers are found in whole grains and vegetables.

17. Carbohydrates-DietaryGuidelines • Choose fiber-rich fruits, vegetables, and whole grains often • Choose and prepare foods and beverages with little added sugars or caloric sweeteners, such as amounts by the USDA Food Guide and DASH Eating Plan • Reduce incidence of dental caries by practicing good oral hygiene and consuming sugar and starch-containing foods and beverages less frequently

20. Digestion and Absorption of Carbohydrates • Carbohydrate Digestion • In the mouth, the salivary enzyme amylase begins to hydrolyze starch into short polysaccharides and maltose. • In the stomach, acid continues to hydrolyze starch while fiber delays gastric emptying and provides a feeling of fullness (satiety).

21. Digestion and Absorption of Carbohydrates • Carbohydrate Digestion • In the small intestine, pancreatic amylase among other enzymes (maltase, sucrase, and lactase) hydrolyzes starches to disaccharides and ultimately monosaccharides. • In the large intestine, fibers remain and attract water, soften stools and ferment.

22. Digestion and Absorption of Carbohydrates • Carbohydrate Absorption • Primarily takes place in the small intestine • Glucose and galactose are absorbed by active transport. • Fructose is absorbed by facilitated diffusion.

23. Digestion and Absorption of Carbohydrates • Lactose Intolerance • Symptoms include bloating, abdominal discomfort, and diarrhea. • Causes include lactase deficiency due to a natural decrease that occurs with aging or damaged intestinal villi. • Prevalence • Lowest in Scandinavians and northern Europeans • Highest in Southeast Asians and native North Americans

24. Digestion and Absorption of Carbohydrates • Lactose Intolerance - Dietary Changes • Increase consumption of milk products gradually. • Mix dairy with other foods. • Spread dairy intake throughout the day. • Use of acidophilus milk, yogurt, and kefir (fermented products) • Use of enzymes • Individualization of diets • Must be careful that vitamin and mineral deficiencies do not develop

25. Glucose in the Body • The Constancy of Blood Glucose • Maintaining Glucose Homeostasis • Low blood glucose may cause dizziness and weakness. • High blood glucose may cause fatigue. • Extreme fluctuations can be fatal.

26. Glucose in the Body • A Preview of Carbohydrate Metabolism • The body stores glucose as glycogen in liver and muscle cells. • The body uses glucose for energy if glycogen stores are available. • If glycogen stores are depleted, the body makes glucose from protein. • Gluconeogenesis converting protein to glucose. • Protein-sparing action is having adequate carbohydrate in the diet to prevent the breakdown of protein for energy.

27. Blood Glucose Regulation High Blood Sugar Dietary CHO • Muscles • Used as fuel • To glycogen Insulin Pancreas Glucagon Liver Liver • Used as fuel • To Glycogen • To Fat Low Blood Sugar • Glycogenolysis • Gluconeogenesis

29. Glucose in the Body • A Preview of Carbohydrate Metabolism • Making ketone bodies from fat fragments • The accumulation of ketone bodies in the blood is called ketosis. • Ketosis upsets the acid-base balance in the body. • The body can use glucose to make body fat when carbohydrates are consumed excessively.

30. Glucose in the Body • The Constancy of Blood Glucose • The Regulating Hormones • Insulin moves glucose into the cells and helps to lower blood sugar levels. • Glucagon brings glucose out of liver storage and raises blood sugar levels. • Epinephrine acts quickly to bring glucose out of liver storage during times of stress and stimulates gluconeogenesis.

31. Glucose in the Body • The Constancy of Blood Glucose • Balance glucose within the normal range by eating balanced meals regularly with adequate complex carbohydrates. • Blood glucose can fall outside the normal range with hypoglycemia or HYPERGLYCEMIA (diabetes).

32. Glucose in the Body • The Constancy of Blood Glucose • Diabetes • Type 1 diabetes is the less common type with no insulin produced by the body. • Type 2 diabetes is the more common type where fat cells resist insulin. • Prediabetes is blood glucose that is higher than normal but below the diagnosis of diabetes. • Hypoglycemia is low blood glucose and can often be controlled by dietary changes.

33. Glucose in the Body • The Constancy of Blood Glucose • Glycemic response is how quickly the blood glucose rises and elicits an insulin response. • Glycemic index classifies foods according to their potential for raising blood glucose. • Glycemic load refers to a food’s glycemic index and the amount of carbohydrate the food contains. The benefit of the glycemic index is controversial.

34. Glycemic Index • is a ranking system for carbohydrates based on their immediate effect on blood glucose levels. It compares carbohydrates gram for gram in individual foods, providing a numerical, evidence-based index of postprandial (post-meal) glycemia.

35. The effect on blood glucose from a high versus low glycemic index carbohydrate.

36. Glycemic Index of selected Foods

37. Glycemic Load • The glycemic load (GL) is a ranking system for carbohydrate content in food portions based on their glycemic index (GI) and the portion size. • The usefulness of glycemic load is based on the idea that a high glycemic index food consumed in small quantities would give the same effect as larger quantities of a low glycemic index food on blood sugar

40. Health Effects and Recommended Intakes of Sugars • Sugar poses no major health problem except dental caries. • Excessive intakes may displace nutrients and contribute to obesity. • Consuming foods with added sugars should be limited. • Naturally occurring sugars from fruits, vegetables and milk are acceptable sources.

41. Health Effects and Recommended Intakes of Sugars • Health Effects of Sugars • Foods with added sugars have sugars listed as a first ingredient. • Nutrient deficiencies may develop from the intake of empty kcalories. • Just because a substance is natural does not mean it is nutritious. (Example: honey) • Dental caries may be caused by bacteria residing in dental plaque and the length of time sugars have contact with the teeth.

42. Health Effects and Recommended Intakes of Sugars • Controversies Surrounding Sugars • Excessive sugar intake can contribute to the development of body fat. • Sugar may be able to alter blood lipid levels and contribute to heart disease • There is no scientific evidence that sugar causes misbehavior in children and criminal behavior in adults. • There is a theory that sugar increases serotonin levels, which can lead to cravings and addictions.

43. Health Effects and Recommended Intakes of Sugars • Recommended Intakes of Sugars • The USDA Food Guide states that added sugars can be included in the diet as part of discretionary kcalories. • Dietary Guidelines state to limit intake of foods and beverages that are high in added sugars. • DRI suggest added sugars should contribute no more than 25% of a day’s total energy intake.

44. Health Effects and Recommended Intakes of Starch and Fibers • Health Effects of Starch and Fibers • May be some protection from heart disease and stroke • Soluble fibers bind with bile and thereby lower blood cholesterol levels. • Fiber may also displace fat in the diet. • Reduce the risk of type 2 diabetes by decreasing glucose absorption • Enhance the health of the GI tract which can then block the absorption of unwanted particles • May protect against colon cancer by removing potential cancer-causing agents from the body

45. Health Effects and Recommended Intakes of Starch and Fibers • Health Effects of Starch and Fibers • Promote weight control because complex carbohydrates provide less fat and added sugar. • Harmful effects of excessive fiber intake • Displaces energy and nutrient-dense foods • Abdominal discomfort and distention • May interfere with nutrient absorption

46. Recommended Intakes of Starch and Fibers • RDA for carbohydrate is 50-100 g per day, or 45-65% of energy intake. • Daily Value is 300 grams per day. • Dietary Guidelines encourage a variety of whole grains, vegetables, fruits and legumes daily. • Healthy People 2010 recommends six servings of grains and five servings of fruits and vegetables.

47. Health Effects and Recommended Intakes of Starch and Fibers • Recommended Intakes of Fiber • FDA recommends 25 grams for a 2,000-kcalorie diet. • DRI at 14 g per 1000 kcalorie intake (28 grams for a 2,000 kcalorie diet) • American Dietetic Association recommends 20-35 g per day. • World Health Organization suggests no more than 40 g per day.

49. Recommended Intakes of Starch and Fibers • From Guidelines to Groceries • Grains – encourage whole grains • Vegetables – starchy and nonstarchy vegetables differ in carbohydrate content • Fruits – vary in water, fiber and sugar content • Milks and Milk Products – contain carbohydrate; cheese is low • Meat and Meat Alternates – meats are low but nuts and legumes have some carbohydrate • Food labels list grams of carbohydrate, fiber and sugar; starch grams can be calculated.