Class website… kind of

1. Class website… kind of • http://bio200-nutrition.wikispaces.com/ • Has all of the past lectures, syllabus, disease list,important reminders etc. • We will be using this for the time being. • Eventually will be replaced with professors online

2. Carbohydrates: Part 2 Will Brown Lecture 5 1/127/2012

3. Outline and Content • Objective – To identify basic structure, sources, and digestion of carbohydrates. Also to identify the role of carbs and some of the issues associated with to little or to much • Content • Finish up with alternative sweeteners • Making carbs available • Role of carbohydrates in the body • Glycemic index and glycemic load

4. Tagatose • Brand name = Naturlose® • Altered form of fructose • Poorly absorbed • Yields 1.5 kcal/g • Eventually fermented in LI so thought to act as prebiotic

5. Stevia • Brand name = Sweet Leaf® • Derived from South American shrub • 100-300 times sweeter than sucrose • Provides no energy • Available in Japan since ‘70s but not approved in US till 2008

6. Digestion and absorption of carbs

7. Digestion of Carbs • Where does the breakdown of carbohydrates begin? • Begins with cooking • Heat will break down some of the connective structure • Food is easier to chew • Starch molecules will absorb water causing them to swell • Easier to digest

8. Digestion of Carbs: quick review • Mouth • mechanical breakdown by chewing • Chemical breakdown by salivary amylase-short lived • Stomach • Salivary amylase inactivated by acid • No further digestion of carbs occurs in the stomach

9. Digestion of Carbs: quick review • Pancreas • Enzymes released into SI • Enzymes (more amylase) breakdown starch to maltose • Small Intestine • Enzymes in lining breakdown disaccharides into monosaccharides • Maltase, sucrase, and lactase • Absorption of monos heads to the liver for processing

10. Digestion of Carbs: quick review • Large Intestine • Viscous fiber is fermented into acids and gases by bacteria • Rectum and Anus • Nonfermentable fiber excreted • Little other dietary carbs remain

11. Absorption of Carbs • Disaccharides are broken down by absorptive cells • Glucose and Galactose are taken up by active transport • Fructose is taken up by facilitated diffusion • Not absorbed as fast • Large amounts of fructose can result in diarrhea

12. Absorption of Carbs • Once in the absorptive cells, some fructose is converted to glucose • Small fraction • All monosaccharides transported to the liver via the portal vein • What are the functions of the liver in carbohydrate availability to the body? • Metabolize fructose and galactose to glucose • Release glucose into blood stream • Store glucose by producing glycogen • May produce fat – only if extreme caloric excess

13. Lactose Maldigestion and Intolerance • Reduced ability or complete inability to digest lactose • Results in reduced lactase production by absorptive cells • Symptoms are caused by excess gas produced by the fermentation of lactose by bacteria in the gut • When symptoms are severe then called “intolerance” • Affects ~25% of adults • Begins in early childhood and progresses through adulthood • More predominant in those from Asian, African, or Latino descent

14. Lactose Maldigestion and Intolerance • Most people can handle some amounts of lactose - ~1/2 to 1 cup with a meal • What are some health impacts of lactose maldigestion and intolerance? • ↓milk comsuption = ↓ Ca+ and Vit. D • ↑ discomfort caused by excess gas • What are some ways to handle it? • Eat foods with Lactase in them • Drink milk with fatty meal • Eat foods with bacteria in them; i.e: yogurt • Lactase pills

15. The role of carbs in the body

16. Digestible carbs in the body • Remember from previous lecture the difference between digestible and indigestible carbs? • What is the main monosaccharide in the body? • Glucose • What is the primary role of glucose in the body? • Provide fuel/energy to the body

17. Digestible carbs in the body • What happens when not enough carbs are present in the diet? • The body breaks down fat – process known as Ketosis • Produces ketone bodies • Can disrupt acid-base balance in the blood • Debate about health issues - argument against low-carb diets • The body can also breakdown protein – usually only in extreme cases like extreme starvation • Results in protein being catabolized from tissues; i.e; muscle, kidney, liver and heart • Can lead to system failure • Primary cause of death in eating disorders? Heart failure due to breakdown of cardiac tissue

18. Regulating glucose Hyperglycemia Elevated blood glucose 125 mg/dL Glucose uptake by cells Pancreas releases insulin Glucose converted to Glycogen 100 mg/dL Normal Glucose Levels Concentration of Glucose in blood (milligrams/deciliter) 70 mg/dL Increased gluconeogenesis Pancreas releases Glucagon Glycogen broken down to Glucose Low blood glucose 50 mg/dL Hypoglycemia

19. Regulating Glucose • Under tight regulation by liver and pancreas • Liver controls glucose ↔ gylcogen conversion • Pancreas secretes hormones • Insulin • Glucagon • When is insulin released and what are insulin’s effects on blood glucose? • Released after a meal • On liver-causes conversion of glucose to glycogen • On cells-causes uptake of glucose

20. Regulating Glucose • When is glucagon released and what are glucagon’s effects on blood glucose levels? • Released when blood glucose levels fall below 70 mg/dL • Caused liver to convert glycogen to glucose • Epinephrine also elevates blood glucose levels • Released by adrenal glands due to perceived threat • Causes liver to increase glycogen breakdown

21. Hyperglycemia/Hypoglycemia:The two extremes • Hyperglycemia-severely elevated blood glucose levels; >125 mg/dL • Hypoglycemia-severely low blood glucose levels; < 50 mg/dL • Usually caused by hormone imbalance; i.e: reduced insulin production in type 1 diabetics

22. Glycemic Index and Glycemic Load

23. Glycemic index • Different foods increase blood glucose levels differently • Kraft Mac N’ Cheese vs. Chili • Why care about the impacts of different carbohydrate sources on blood glucose? • Sources that cause quick elevations cause big spikes in insulin • Chronically high insulin results in a host of problems • Increased fat deposition • Resistance of insulin’s effects on muscle tissues

24. Glycemic Index • Ratio of blood glucose response of a food compared to a standard – usually glucose or white bread • Examples of high GI foods – baked potatos, short grain white rice, and mashed potatos • Examples of low GI foods – Carrots, skim milk and bread • Problem – based on the serving of food that would deliver 50 g of carbs • May not reflect the typical serving of food

25. Glycemic Load • Takes into account the glycemic index and the amount of carbs consumed • Considered more reflective of the effects on blood glucose levels • How to calculate: Glycemic Load = (Glycemic Index) x (Grams of carbs consumed)100 Example: Baked Potato (1 cup) GI=85Carbs (g) = 57 (85*57)/100=48

26. What to do with GI and GL… • Try to reduce the amount of high GI or GL foods • Don’t eat too many high GI foods at one meal • Substitute one High GI food for Low GI foods at every meal • Eat a combination of high GI with low GI • Increase physical activity