Thomas O. Henderson, Ph. D. Professor Emeritus Dept. of Biochemistry & Molecular Genetics

1. Thomas O. Henderson, Ph. D. • Professor Emeritus • Dept. of Biochemistry & • Molecular Genetics • Office: 321 CMW • Phone: 6-5978 • email: revtotis@uic.edu

2. Macronutrients • Lecture 2 Carbohydrates & Fiber • Lecture 3 Fats (Lipids) • Lecture 4 Proteins

3. From MMWR 53, No. 4; February 6, 2004

4. Macronutrients I • Overview • Carbohydrates • Fiber

5. 2002 IOM-FNB Guidelines for Macronutrients • Goal of new recommendation “to meet the body’s daily energy and nutritional needs while minimizing risks for chronic disease.” • Guidelines set for macronutrients: carbohydrates, fats, proteins • For first time, DRI’s set for dietary fiber and essential fatty acids (n-3 & n-6) • Guidelines set for exercise

6. Acceptable Macronutrient Distribution Range (AMDR) • AMDR just another way of stating the % of calories from a given class of macronutrient • 2002 recs adults ≥19 years: % of daily calories Carbohydrates 45 - 65 Fats 20 - 35% Proteins 10 - 35% • ≤25% of total calories from “added sugar”

7. AMDR (continued) • Recommendations more flexible than in past • Ranges set so that total dietary intake would be of breadth and quality to insure intake of essential nutrients (i.e., vitamins & minerals) • Diets very low in either carbs or fat likely to be deficient in one or more essential nutrient

8. AMDR (continued) When fat intakes are low and carb intake is high: • HDL is reduced • ratio of plasma cholesterol:HDL increased • plasma triacylglycerol (TAG) increased These all consistent with increased risk of coronary heart disease (CHD; CAD)

9. AMDR (continued) • When fat intakes are high, people gain weight • Can exacerbate health of persons already susceptible to obesity, particularly risk of CHD and Type II diabetes • High fat diets usually associated with increased intake of saturated fatty acids • The latter, in turn, can increase LDL levels and thereby increase risk of CHD

10. All Fatty Acids are NOT Equal! If fat intake is at high end of 20 -35% range, one would be well advised to • limit intake of cholesterol and saturated and trans fatty acids • replace them with monounsaturated and polyunsaturated fatty acids

11. Carbohydrates • 2002 IOM-FNB report set RDA for intake of digestible carbohydrate • for ages 1 - >70, 130 g/d recommended • 175 & 210 g/d for lactating and pregnant women, respectively • for 0 - 6 months, AI set at 60 g/d • for 7 - 12 months, AI set at 95 g/d

12. RDA (& AI) for carbs based on minimum amount needed to provide glucose for brain function • Most of us regularly exceed RDA • AMDR set at 45 - 65% of calories/day • No more than 25% of calories/day from “added sugars” • Emphasis should be on obtaining bulk of daily carbs from fruits, vegetables, and minimally processed whole grains and whole grain products

13. Major Sources of Carbohydrates • disaccharides (sucrose, lactose) • starch (amylose & amylopectin) • minor, variable amounts of glycogen (in meats), maltose, trehalose (mushrooms), raffinose (legumes) • very little monosaccharide in natural diet • increased amounts of added fructose (high-fructose corn syrup or solids)

15. Forms of Starch Amylose Amylopectin Cellulose (NOT a form of starch)

16. On a Food Label, Sugars Include: brown sugar invert sugar corn sweetener lactose corn syrup maltose fructose molasses fruit juice concentrate raw sugar glucose (dextrose) [table] sugar (sucrose) high-fructose corn syrup syrup honey

17. Consequences of chronic elevation in concentration of hexoses in blood 2 possible consequences are • enzymatic formation of sugar alcohols • nonenzymatic glycosylation (“glycation”) of proteins • Both of these associated with long term pathologies of nerves, blood vessels, kidneys, and lens as found in diabetes and galactosemia

18. Sugar Alcohols • Aldose reductase and polyol dehydrogenase involved • Isozymes of aldose reductase found in most tissues • Especially high in Schwann cells of peripheral nerves, kidney papillae, and lens epithelium

20. Ways in which sugar alcohols cause cell damage and pathologies not known However, since they do not diffuse out of cells very readily, they can cause cell damage by cellular swelling associated with osmosis The enzymatic reactions are reversible so that favored direction is determined by substrate/product concentrations (i. e., “mass action”)

21. Protein glycosylation (glycation) • nonenzymatic process • get advanced glycosylation product formation (“AGE products”) with proteins • quite possible that glycosylation of DNA occurs also

22. An estimate of how well a diabetic patient has controlled her/his hyperglycemia over past 5-6 weeks can be made by measuring extent of hemoglobin glycosylation (HbA1c) • Recall - RBC hemoglobin has lifespan of ~120 days • Shorter or more recent periods can be estimated by measuring albumin glycosylation

24. Galactose Metabolism • By far major source of galactose in human diet is in form of lactose • Major source of lactose is milk and milk products • Major organ involved in galactose metabolism is liver • There are several inborn errors involving metabolism of galactose

25. Lactase deficiency (aka Hypolactasia)(lactose or milk intolerence) • In most mammals, including the great majority of humans, lactase activity disappears after weaning or at the latest during adolescence. • In the case of humans, especially true for Southeast Asians and Africans. • About 70% of African-Americans, >80% of Chinese and >70% of Mexicans are lactose intolerant • In contrast, lactase deficiency uncommon in Northwest Europeans such as Scandinavians (~3% of Danes)

26. 2 types of galactosemia are caused by deficiency or absence of: D-galactose 1-P uridyltransferase and galactokinase • The first more common (prevalence = 1 in 70,000) than second (prevalence = 1 in 1 x 105) and has far greater clinical importance in terms of associated pathologies, especially in homozygotes • In Illinois the incidence of the first defect is ~1 in 30,000 live births

27. Definitions: Incidence = 1 in n live births Prevalence = 1 in n people

29. The pathologies associated with defective D-galactose 1-P uridyl transferase include: • severe mental retardation, hepatomegaly, cataracts, and non-specific morphological changes in the CNS • In Illinois, all newborns are screened for galactosemia • Affected infants MUST be placed on a galactose-free (i. e., milk-free) diet immediately to prevent irreversible damage

30. Fructose Metabolism • Major sources of fructose in diet are fruits, honey, sucrose and, now, in form of high fructose corn syrup or solids as an added sweetener in soft drinks, candy, etc. • Fructose -in one form or another- may account for 30 - 60% of total dietary carbohydrates for some • Major organ involved in fructose metabolism is the liver

31. There are two (rare) inherited diseases of fructose metabolism • Essential fructosuria - caused by deficiency in fructokinase and leads to transitory elevation of blood fructose level and to fructosuria (fructose in the urine) • Fructose intolerance - MUCH MORE SERIOUS EFFECTS similar to those associated with galactosemia - caused by a defect in fructose-1-P aldolase (aldolase B) • In fructose intolerance fructose and its sources (sucrose!) must be eliminated from diet

32. Essential Fructosuria Fructose Intolerance

33. “Baby Bottle” Caries

34. “Baby Bottle” Caries. Rampant caries due to use of sugar-sweetened beverages in nursing bottle as a pacifier From Nutrition in Clinical Dentistry, 3/ed, 1989, A. E. Nizel and A. S. Papas (W. B. Saunders), Fig. 3-7, p. 46.

35. Glycemic Index (GI) Glycemic index of a carbohydrate defined as incremental area under blood glucose response curve of a 50g carbohydrate portion of a test food expressed as a percentage of the response to the same amount of carbohydrate from a standard food (usually glucose or white bread) taken by the same subject. • An abbreviated table of GI’s found on p. 8 of Macronutrient I handout

36. In general, carbohydrate-containing foods such as whole grains, legumes, fruits, vegetables have low GI’s • Amylose form of starch has lower GI than amylopectin • Broadly speaking about grain products, the greater the processing, the higher the GI

37. Factor Influencing GI Number of factors influence GI besides amount or type of carbohydrate in a meal. In a multi-component food or meal, these include: • amount & type of carbohydrate • nature of starch • presence or absence of fat, protein, fiber • how food was prepared • Table of factors influencing GI found on p. 8 of Macronutrient I handout

38. Diabetes Care 27, Supplement 1,pp. S36 - S46, January 2004 American Diabetes Society issued Position Statement entitled “Evidence-Based Nutrition Principles and Recommendations for the Treatment and Prevention of Diabetes and Related Complications” • The panel concluded, “If there are long term effects (of carbohydrate intake) on glycemia and serum lipids, these effects appear to be modest.” • Their position is that recommendations on intake of carbohydrates (and monounsaturated fat) should be individualized for each diabetic patient

39. Dietary Fiber • Defined as nondigestible carbohydrates & lignin intrinsic and intact in plants • Functional fiber defined as isolated nondigestible carbohydrates that have been shown to have beneficial effects in humans • Total fiber: dietary fiber + functional fiber • AI 38g/d for men ages 14 - 50 y; 25g/d for women ages 19 - 50 y • Tables for Total Fiber DRI (AI) and sources of fiber on p. 9, Macronutrient I handout

40. Viscous Fiber • Some types of fiber form highly viscous solutions (viscous fiber) • Viscous fibers delay gastric emptying of ingested foods into small intestine • This produces sensation of fullness • Delayed gastric emptying also results in reduced postprandial blood glucose levels

41. Intake of even moderate amounts of viscous fiber is associated with lowering plasma cholesterol levels • They apparently interfere with absorption of dietary fat and cholesterol and enterohepatic circulation of bile acids and cholesterol

42. Viscous fibers includes pectins, various gums, mixed-linkage -glycans, psyllium, agar, and carrageenan • Oat bran, barley, legumes and various vegetables are good sources of viscous fiber • Isolated fibers or fiber sources that are not viscous (e.g., cellulose, corn and wheat bran) rarely found to lower plasma cholesterol levels