1. Chapter 10 Lecture The Science of Nutrition Third Edition © 2014 Pearson Education, Inc. Nutrients Involved in Antioxidant Function and Vision

2. © 2014 Pearson Education, Inc. What Are Antioxidants? Compounds that protect cells from the damage caused by oxidation –hence, "anti"-oxidation Nutrients with antioxidant properties: –Vitamin E –Vitamin C –Vitamin A (precursor beta-carotene) –Selenium

3. © 2014 Pearson Education, Inc. Exchange Reactions Oxidation is a chemical reaction in which atoms lose electrons Reduction occurs when atoms gain an electron

4. © 2014 Pearson Education, Inc.

5. Free Radicals Stable atoms have an even number of electrons (pairs) orbiting Electron loss during oxidation leaves an odd number or unpaired electron Unstable atoms are called free radicals Reactive oxygen species (ROS): oxygen molecule that becomes a free radical

6. © 2014 Pearson Education, Inc.

7. What Causes Free Radicals? Metabolic processes –Immune system fighting infections Environmental factors –Pollution –Excess sunlight –Toxic substances –Radiation –Tobacco smoke –Asbestos

8. © 2014 Pearson Education, Inc. Free Radical Damage Can destabilize other molecules and damage cells Cell membrane damage: –Free radicals form within the phospholipid bilayers of cell membranes and steal electrons –Damaged lipid molecules cause cell membrane to lose its integrity –Causes damage to the cell and all systems affected by the cell

9. © 2014 Pearson Education, Inc.

10. Diseases Linked with Free Radicals Free radicals damage low-density lipoproteins (LDLs), cell proteins, and DNA Increase risk for chronic diseases, including: –cancer –heart disease –type 2 diabetes –arthritis –cataracts –Alzheimer's and Parkinson's diseases

11. © 2014 Pearson Education, Inc. How Do Antioxidants Work? Stabilize free radicals or oppose oxidation Antioxidant vitamins donate their electrons or hydrogen molecules to free radicals to stabilize them and reduce oxidation damage Antioxidant minerals act as cofactors within enzyme systems that convert free radicals to less damaging substances that can be excreted Phytochemicals help stabilize free radicals

12. © 2014 Pearson Education, Inc. Antioxidant Enzymes Antioxidant enzymes/enzyme systems: –Break down oxidized fatty acids –Make more vitamin antioxidants available to fight other free radicals

13. © 2014 Pearson Education, Inc. Antioxidant Enzymes (continued) Antioxidant enzymes: –Superoxide dismutase converts free radicals to less damaging substances, such as hydrogen peroxide –Catalase removes hydrogen peroxide from the body –Glutathione peroxidase removes hydrogen peroxide

14. © 2014 Pearson Education, Inc. Nutrients as Antioxidants Certain compounds stabilize free radicals and prevent damage to cells and tissues Nutrients with antioxidant properties include: –Vitamin E –Vitamin C –Beta-carotene (phytochemical and precursor to vitamin A) –Vitamin A –Selenium

15. © 2014 Pearson Education, Inc.

16. Vitamin E Fat soluble, absorbed with dietary fats Incorporated into the chylomicron to be transported to the liver Incorporated into very-low-density lipoproteins (VLDLs) Stored in adipose tissue, cell membranes

17. © 2014 Pearson Education, Inc. Forms of Vitamin E Tocopherol compounds are the biologically active forms Alpha-tocopherol is most active (potent), found in food and supplements RDA: expressed as alpha-tocopherol (mg/day) Food labels and supplements: expressed as alpha-tocopherol equivalents or International Units (IU)

18. © 2014 Pearson Education, Inc.

19. Functions of Vitamin E Protects polyunsaturated fatty acids (PUFAs), fatty cell components, and LDLs from oxidization (lower heart disease risk) Added to oil-based foods and skincare products to reduce rancidity and spoilage Normal nerve and muscle development Enhances immune system Promotes vitamin A absorption, if low

20. © 2014 Pearson Education, Inc. RDA for Vitamin E RDA: 15 mg alpha-tocopherol per day Determined to be sufficient to prevent erythrocyte hemolysis, rupturing (lysis) of red blood cells (erythrocytes) Tolerable Upper Intake Level (UL): 1,000 mg alpha-tocopherol per day

21. © 2014 Pearson Education, Inc. Food Sources of Vitamin E Vitamin E is abundant in plant-based foods –Vegetable oils (safflower, sunflower, canola, soybean), mayonnaise, salad dressing –Nuts, seeds, soybeans –Wheat germ, fortified cereals –Vitamin E is destroyed by exposure to oxygen, metals, ultraviolet light, and heat –Little vitamin E in deep-fried, processed foods

22. © 2014 Pearson Education, Inc.

23. Vitamin E Toxicity High supplemental doses of vitamin E may be harmful for certain individuals Side effects: nausea, intestinal distress, and diarrhea Interacts with anticoagulants (aspirin, Coumadin) Long-term use may cause hemorrhagic stroke

24. © 2014 Pearson Education, Inc. Vitamin E Deficiency Deficiency is rare Erythrocyte hemolysis (rupturing of red blood cells) leads to anemia Anemia in premature infants Symptoms: loss of muscle coordination and reflexes; impaired vision, speech Impaired immunity (with low selenium) Associated with fat malabsorption

25. © 2014 Pearson Education, Inc. Vitamin C and Its Functions Water soluble Functions—synthesis of: –Collagen (prevents scurvy) –DNA –Bile –Neurotransmitters (serotonin) –Carnitine (transports long-chain fatty acids) –Hormones (thyroxine, epinephrine, steroids)

26. © 2014 Pearson Education, Inc.

27. More Functions of Vitamin C Antioxidant for protecting: –LDL-cholesterol from oxidation –Lungs from ozone and cigarette damage –White blood cells (enhances immune function) Reduces nitrosamines, cancer-causing agent found in cured and processed meats Regenerates oxidized vitamin E Enhances iron absorption

28. © 2014 Pearson Education, Inc.

29. Vitamin C Requirements RDA: 90 mg/day (men), 75 mg/day (women) UL: 2,000 mg/day for adults Smokers require additional 35 mg/day Other situations requiring more vitamin C: –Healing from traumatic injury, surgery, burns –Use of oral contraceptives

30. © 2014 Pearson Education, Inc. Food Sources of Vitamin C Best sources: fresh fruits and vegetables Destroyed by heat and oxygen Can be leached into boiling water Minimize loss: steaming, microwaving, and stir- frying

31. © 2014 Pearson Education, Inc.

32. Too Much Vitamin C? Water soluble –Extra excreted; consuming excess is not toxic –Only supplements can lead to toxic doses Megadoses –Long-term excess of 2,000 mg/day: nausea, diarrhea, nosebleeds, and abdominal cramps –Harmful for people with hemochromatosis (excess iron accumulation in the body)

33. © 2014 Pearson Education, Inc. Not Enough Vitamin C? Rare in developed countries Scurvy: most common deficiency disease Symptoms: bleeding gums, loose teeth, weakness, wounds that fail to heal, bone pain and fractures, diarrhea, depression Anemia can result High risk for deficiency among people with –Low fruit and vegetable intake –Alcohol and drug abuse

34. © 2014 Pearson Education, Inc. Beta-Carotene Provitamin A, inactive form (precursor) of vitamin A to be converted to active retinol Phytochemical classified as a carotenoid Expressed in food as Retinol Activity Equivalents (RAE), which indicates how much active vitamin A is available to the body after conversion

35. © 2014 Pearson Education, Inc.

36. Functions of Beta-Carotene Weak antioxidant Fights lipid oxidation in cell membranes Enhances immune system Protects skin from UV-ray damage Protects eyes from damage, preventing or delaying age-related vision impairment

37. © 2014 Pearson Education, Inc. Beta-Carotene Requirements Beta-carotene is not an essential nutrient No RDA established Consuming 6 to 10 mg of beta-carotene per day from food sources may reduce risks for cancer and heart disease Food sources: red, orange, yellow, and deep- green fruits and vegetables Heat improves digestibility and absorption

38. © 2014 Pearson Education, Inc.

39. Beta-Carotene Requirements Large consumption is not toxic –Carotenosis (carotenodermia): reversible and harmless –Supplementation is not recommended; adequate amounts from fruits and vegetables Not enough? –No known deficiency symptoms

40. © 2014 Pearson Education, Inc. Vitamin A Fat soluble Active forms: retinol, retinal, retinoic acid Stored mainly in the liver Expressed as Retinol Activity Equivalents (RAE) International Units (IU) for vitamin A on food labels or dietary supplements

41. © 2014 Pearson Education, Inc.

42. Functions of Vitamin A Antioxidant; scavenges free radicals and protects LDL from oxidation Essential for healthy vision Cell differentiation, process by which stem cells mature into specialized cells Sperm production and fertilization Bone growth

43. © 2014 Pearson Education, Inc.

44. Vitamin A Requirements RDA is 900 micrograms/day for men, 700 micrograms/day for women UL: 3,000 micrograms/day preformed vitamin A Food sources –Animal (liver, eggs, dairy, fortified foods) –Plants (dark-green, orange, and deep-yellow fruits and vegetables that are high in beta- carotene can be converted to vitamin A)

45. © 2014 Pearson Education, Inc.

46. Vitamin A Toxicity Can be highly toxic, mainly from supplements –Birth defects, spontaneous abortion –Symptoms: fatigue, loss of appetite, blurred vision, hair loss, skin disorders, bone and joint pain, abdominal pain, nausea, diarrhea, and damage to the liver and nervous system

47. © 2014 Pearson Education, Inc. Vitamin A Requirements Deficiency can result in: –Night blindness –Xerophthalmia –Hyperkeratosis –Impaired immunity, failure of normal growth

48. © 2014 Pearson Education, Inc.

49. Selenium Trace mineral needed in small amounts Antioxidant (part of glutathione peroxidase enzyme system): spares vitamin E Thyroxine (thyroid hormone) production: basal metabolism, body temperature RDA: 55 µg/day UL: 400 µg/day Sources: organ meats, pork, seafood

50. © 2014 Pearson Education, Inc.

52. Selenium Requirements Toxicity can occur from supplements –Brittle hair and nails, skin rashes, vomiting, nausea, weakness, cirrhosis of the liver Deficiency associated with –Keshan disease, a heart disease –Kashin-Beck disease, deforming arthritis –Impaired immunity

53. © 2014 Pearson Education, Inc. Kashin-Beck disease creates deforming arthritis.

54. © 2014 Pearson Education, Inc. Additional Antioxidants Copper, zinc, and manganese are part of the superoxide dismutase enzyme antioxidant complex Iron is part of the catalase structure Copper, iron, and zinc for blood health Manganese: important cofactor in carbohydrate metabolism

55. © 2014 Pearson Education, Inc. Disorders Related to Free-Radicals: Cancer Cancer: a group of diseases characterized by cells growing "out of control" –cancer cells aggressively invade tissues and organs throughout the body Tumors: immature undifferentiated cell masses that have no physiologic function –malignant (cancerous) –benign (harmless)

56. © 2014 Pearson Education, Inc. Disorders Related to Free-Radicals: Cancer Primary steps of cancer development: –Initiation –Promotion –Progression

57. © 2014 Pearson Education, Inc.

58. Cancer Risk factors –Tobacco use –Overweight, obesity –Poor nutrition (diets high in saturated fats; low in fruits & vegetables; excessive alcohol consumption) –Physical inactivity –Infectious agents –Ultraviolet radiation

59. © 2014 Pearson Education, Inc. A healthy lung (left) and a smoker's lung (right).

60. © 2014 Pearson Education, Inc. Effects of tobacco use include increased risk for mouth cancer (a) and skin wrinkling (b).

61. © 2014 Pearson Education, Inc. Human papillomavirus (HPV).

62. © 2014 Pearson Education, Inc. A malignant melanoma lesion.

63. © 2014 Pearson Education, Inc. Cancer Prevention Antioxidants play a role in cancer prevention –Enhance immune system –Inhibit cancer cell growth –Prevent oxidative damage to cells Eat a varied, healthful diet Be physically active Maintain a healthy body weight Quit smoking or don't start Avoid infectious agents and UV radiation

64. © 2014 Pearson Education, Inc. Cardiovascular Disease (CVD) Leading cause of death in adults (U.S.) Diseases of the heart and blood vessels –Coronary heart disease –Hypertension (high blood pressure) –Atherosclerosis (hardening of the arteries) Primary manifestations of CVD –Heart attack –Stroke

65. © 2014 Pearson Education, Inc. Major Risk Factors for CVD Smoking Hypertension High blood levels of LDL cholesterol Obesity Sedentary lifestyle

66. © 2014 Pearson Education, Inc. Other Risk Factors for CVD Low blood levels of HDL cholesterol Diabetes Family history of CVD –Males before age 55 –Females before age 65 Being male older than 45 years Being postmenopausal woman

67. © 2014 Pearson Education, Inc. Low-Grade Inflammation May be even more important than elevated cholesterol levels Weakens plaque in blood vessels (vessels become more fragile) –Plaques likely to burst, break away, lodge in blood vessels of heart or brain and close off blood supply, resulting in a heart attack or stroke

68. © 2014 Pearson Education, Inc. Low-Grade Inflammation C-reactive protein (CRP) –Marker for inflammation (blood test) –Associated with high risk for heart attack in the presence of normal cholesterol levels –High CRP and high cholesterol can increase the risk for heart attack

69. © 2014 Pearson Education, Inc. Antioxidants and CVD Antioxidants (vitamins E and lycopene) reduce damage to blood vessels: –Scavenge free radicals –Reduce low-grade inflammation –Reduce blood coagulation and clot formation In fruits, vegetables, and whole grains –Dietary fiber (soluble):oatmeal and oat bran –Folate (reduce homocysteine-CVD risk factor) –Others (flavonoids): tea