Chapter 4 CARBOHYDRATES

1. Chapter 4 CARBOHYDRATES FRIEND OR FOE?

2. What are carbohydrates? Carbo-hydrate means carbon and water (C + H2O). For every carbon there is 1 water molecule or 2 hydrogen atoms and 1 oxygen atom. 2 categories: Simple carbohydrates = Complex carbohydrates =

3. Where do carbohydrates come from? Plants and photosynthesis Chlorophyll captures light energy which is transformed into chemical energy - ATP Chemical energy is used to combine CO2 and H2O to form glucose. **The by-product is oxygen. Extra glucose is stored in plants as starch. **Plants are the base of the food chain for all living things.

4. FIGURE 4-1: CARBOHYDRATE�MAINLY GLUCOSE�IS MADE BY PHOTOSYNTHESIS. The sun�s energy becomes part of the glucose molecule�its calories, in a sense. In the molecule of glucose on the leaf here, black dots represent the carbon atoms; bars represent the chemical bonds that contain energy. FIGURE 4-1: CARBOHYDRATE�MAINLY GLUCOSE�IS MADE BY PHOTOSYNTHESIS. The sun�s energy becomes part of the glucose molecule�its calories, in a sense. In the molecule of glucose on the leaf here, black dots represent the carbon atoms; bars represent the chemical bonds that contain energy.

5. Carbohydrates used by man Sugars (saccharides), fig 4.2 Monosaccharides (single sugars, 6 carbons) Glucose � Fructose � Galactose � In the body, fructose and galactose are converted to glucose. Why is it better to ingest sugar in fruits than as refined sugar?

6. Carbohydrates used by Man Sugars cont�d Disaccharides (two sugars joined together chemically, 12 carbons) Sucrose � glucose + fructose, table sugar & honey. Used as the transport sugar in plants Maltose � glucose + glucose, found in grains. Lactose � glucose + galactose, found in milk.

7. FIGURE 4-2: HOW MONOSACCHARIDES JOIN TO FORM DISACCHARIDES.FIGURE 4-2: HOW MONOSACCHARIDES JOIN TO FORM DISACCHARIDES.

8. Carbohydrates used by man Polysaccharides (means many sugars or 3 or more sugars), fig 4.3. Starch Glycogen

9. Carbohydrates used by Man Polysacchrides cont�d Fiber - chains of glucose joined differently than starch and glycogen. Support and retain water in plants. Soluble fiber � dissolves in water and is digestable. Pectin, gums, mucilages Insoluble fiber � does not dissolve in water, less digestable. Cellulose, hemicellulose

10. FIGURE 4-3: HOW GLUCOSE MOLECULES JOIN TO FORM POLYSACCHARIDES.FIGURE 4-3: HOW GLUCOSE MOLECULES JOIN TO FORM POLYSACCHARIDES.

11. Do we really need carbohydrates? Glucose is the preferred fuel for many of our cells including our brain and the rest of the nervous system. Carbohydrates are attached to lipids and proteins. They act as cell identity markers and are required to activate some proteins. Carbohydrates (includes fiber) often occur in food (fruits and vegetables) with water, vitamins, minerals, phytochemicals, and no fat. They are also relatively cheap!

12. Do we really need carbohydrates? Carbohydrates and weight loss: carbohydrates have fewer calories per gram than fat. Trick: eat in moderation and use complex carbohydrates, not refined sugars. Refined sugar recommendations: no more than 12 tsp/day, less than 10% of calorie intake, Table 4.1. The average current intake in American is 31 tsp/day.

13. Why fiber? (Table 4.2) Decreases the risk of cardiovascular diseases: decreases absorption of cholesterol and bile, and decreases our intake of fatty foods by making us feel full (satiety), fig 4.5. Decreases the risk of developing diabetes: weight maintenance. Helps control blood glucose in established diabetes.

14. Why fiber? Improves health of digestive tract: stimulates muscles, prevents constipation and formation of diverticuli and infections. **Colon cancer and fiber: Previous studies have shown that diets that provide adequate fiber prevent colon cancer. New Study shows that fiber supplements do NOT prevent colon cancer. i.e. Eat your fruits and veges because they seem to have additional chemicals, phytochemicals, that prevent cancer.

15. FIGURE 4-5: ONE WAY FIBER IN FOOD MAY LOWER CHOLESTEROL IN THE BLOOD. In some ways, the liver is like a vacuum cleaner, sucking up cholesterol from the blood, converting the cholesterol to bile, and discharging the bile into its storage bag, the gallbladder. The gallbladder empties its bile into the intestine, where bile performs necessary digestive tasks. In the intestine, some of the bile associates with fiber and is carried out of the body in feces. (a) When the diet is rich in fiber, more cholesterol (as bile) is carried out of the body. FIGURE 4-5: ONE WAY FIBER IN FOOD MAY LOWER CHOLESTEROL IN THE BLOOD. In some ways, the liver is like a vacuum cleaner, sucking up cholesterol from the blood, converting the cholesterol to bile, and discharging the bile into its storage bag, the gallbladder. The gallbladder empties its bile into the intestine, where bile performs necessary digestive tasks. In the intestine, some of the bile associates with fiber and is carried out of the body in feces. (a) When the diet is rich in fiber, more cholesterol (as bile) is carried out of the body.

16. How much fiber? DRI recommendation is 21-38 grams per day depending on gender and age. Average intake in American is � this amount. Good sources of fiber are listed in fig 4.4.

17. FIGURE 4-4: FIBER COMPOSITION OF COMMON FOODS.FIGURE 4-4: FIBER COMPOSITION OF COMMON FOODS.

18. How much fiber? Too much fiber? �Gas� and frequent bowel movements Blockage of digestive tract. Decreases absorption of vital nutrients and appetite. Drink more water with your fiber!! OYO � Read �Consumer Corner� regarding whole grain products vs. refined products.

19. Digestion and Absorption of Carbohydrates The small intestine can only absorb monosaccharides. Starch digestion begins in the mouth with and enzyme, amylase, that breaks it down into disaccharides � continues in storage section of the stomach, fig 4.10. Small intestine � amylase from the pancreas continues starch digestion.

20. Digestion and Absorption of Carbohydrates Disaccharides � are broken down into monosaccharides small intestine by enzymes produced in the walls of the small intestine. Sucrase Maltase Lactase Monosaccharides are absorbed in small intestine and enter the blood stream.

21. Digestion and Absorption of Carbohydrates Blood carries monosaccharides to the liver. All are converted to glucose. Glucose travels to other cells via the blood. Extra glucose is stored as glycogen in the liver and skeletal muscles.

22. FIGURE 4-10: HOW CARBOHYDRATE IN FOOD BECOMES GLUCOSE IN THE BODY.FIGURE 4-10: HOW CARBOHYDRATE IN FOOD BECOMES GLUCOSE IN THE BODY.

23. Digestion and Absorption of Carbohydrates Fiber � soluble vs. insoluble Most fiber is not digested by humans and forms the bulk in our feces. Soluble fiber is broken down by bacteria in our large intestine � good and bad (the gas again).

24. Digestion and Absorption of Carbohydrates Lactose intolerance � lack of the enzyme lactase causes inability to digest lactose in milk products. There are few with complete intolerance, most can ingest small quantities of milk products. Some people are really allergic to milk. This allergy seems to be increasing in infants. Big Problem � calcium deficiency!

25. How do our bodies use glucose? The chemical energy used to produce glucose (in plants) is released as glucose is broken back down into CO2 and H20. Energy is converted to ATP (adenosine triphosphate) which is used by cells to make other molecules, transport and absorb nutrients and eliminate wastes.

26. FIGURE 4-11: THE BREAKDOWN OF GLUCOSE YIELDS ENERGY AND CARBON DIOXIDE. Cell enzymes split the bonds between the carbon atoms in glucose, liberating the energy stored there for the cell�s use. (1) The first split yields two 3-carbon fragments. The two-way arrows mean that these fragments can also be rejoined to make glucose again. (2) Once they are broken down further into 2-carbon fragments, however, they cannot rejoin to make glucose. (3) The carbon atoms liberated when the bonds split are combined with oxygen and released into the air, via the lungs, as carbon dioxide. Although not shown here, water is also produced at each split. FIGURE 4-11: THE BREAKDOWN OF GLUCOSE YIELDS ENERGY AND CARBON DIOXIDE. Cell enzymes split the bonds between the carbon atoms in glucose, liberating the energy stored there for the cell�s use. (1) The first split yields two 3-carbon fragments. The two-way arrows mean that these fragments can also be rejoined to make glucose again. (2) Once they are broken down further into 2-carbon fragments, however, they cannot rejoin to make glucose. (3) The carbon atoms liberated when the bonds split are combined with oxygen and released into the air, via the lungs, as carbon dioxide. Although not shown here, water is also produced at each split.

27. How do our bodies use glucose? In the absence of glucose our bodies use protein (muscles) as fuel. Fat is also potential fuel but requires carbohydrates to be used properly. Without carbs, fat breakdown is incomplete and produces ketone bodies � ketosis. Ketosis � causes the body fluids to become more acidic and this dissolves bone, promotes kidney stones, etc. Can be life threatening in diabetics.

28. How do our bodies use glucose? Hormones Insulin Glucagon

29. How do our bodies use glucose? It is best to control the release of insulin, i.e. surges of insulin in our blood are not healthy. Glycemic Index (GI) � the ability of a food to increase insulin release. Some foods cause a rapid release of insulin while others cause a moderate or slow, sustained release, fig 4.12. The old table showed that Snickers have a lower glycemic index that potatoes. Glycemic load � GI multiplied times grams of carbohydrate.

30. FIGURE 4-12: GLYCEMIC INDEX OF SELECTED FOODS.FIGURE 4-12: GLYCEMIC INDEX OF SELECTED FOODS.

31. How do our bodies use glucose? Extra amounts of glucose are stored as glycogen. Excess amounts of glucose are converted into fat! Why would a person need to increase their intake of carbohydrates? Why would a person need to control their carbohydrate intake?

32. Blood Glucose Normal � 70-110mg/100ml of blood Hyperglycemia � fasting blood glucose > 140mg/100 ml Hypoglycemia � fasting blood glucose < 60 mg/100ml

33. Diabetes Mellitus Type I diabetes: Destruction of the insulin producing cells in the pancreas (autoimmune disease - genetics, viruses, and other toxins have been implicated). Symptoms: polyuria, glucosuria, polydipsia Strikes children and young adults. All are insulin dependent, i.e. must have insulin injections.

34. Diabetes Mellitus Type 2 diabetes: Cells become insulin resistant. Causes: genetic predisposition, obesity) Symptoms � same as for Type I Affects older adults, obese children and adolescents. Often controlled by diet and weight loss, however many must take insulin stimulating drugs or insulin injections.

35. Diabetes Mellitus Complications � both Type 1 and Type 2 Compromised immune system � infections Blindness Loss of limbs Kidney failure

36. Diabetes Mellitus Control Limit carbohydrate intake & protein intake. The exchange system was originally designed for diabetics. Exercise is an important ingredient in the control of diabetes.

37. Hypoglycemia Symptoms - dizziness, confusion, weakness, death Fasting hypoglycemia: Postprandial hypoglycemia: Also occurs with serious diseases.

38. Food Feature How to spot refined sugars in foods Fiber rich foods, fig 4.15

39. FIGURE 4-15: FIBER IN THE FOOD GROUPS.FIGURE 4-15: FIBER IN THE FOOD GROUPS.

40. Controversy OYO What are the verified problems with high sugar intake Artificial sweeteners � good, bad or indifferent?