Understanding Antioxidants: Nutrients, Benefits & Functions

1. 10 Nutrients Involved in Antioxidant Function

2. What Are Antioxidants? • Compounds that protect cells from the damage caused by oxidation • Nutrients with antioxidant properties: • Vitamin E • Vitamin C • Vitamin A (precursor beta-carotene) • Selenium

3. Exchange Reactions • Oxidation is a chemical reaction in which atoms lose electrons • Reduction occurs when atoms gain a electron

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 Free Radical Formation

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

7. Cell Damage • Free radicals form within the phospholipid bilayers of cell membranes and steal electrons • Damaged lipid molecules cause cell membrane to lose its integrity

9. Diseases Linked with Free Radicals • Free radicals damage low-density lipoproteins (LDLs), cell proteins, and DNA • Increase risk for chronic diseases • Heart disease • Various cancers • Diabetes • Cataracts • Alzheimer’s disease • Parkinson’s disease

10. 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

11. Antioxidant Enzymes • Antioxidant enzyme systems • Break down oxidized fatty acids • Make more vitamin antioxidants available to fight other free radicals

12. Antioxidant Enzymes • 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

13. Antioxidants • Other compounds stabilize free radicals and prevent damage to cells and tissues • Nutrients with antioxidant properties: • Vitamin E • Vitamin C • Vitamin A • Beta-carotene (precursor to vitamin A) • Selenium

14. 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

15. 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)

17. 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

18. 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

19. Food Sources of Vitamin E • Vitamin E is widespread in 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. 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

23. 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

24. 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. 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. 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

29. 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. 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)

32. 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

33. 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. 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

36. 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 the risks for cancer and heart disease • Food sources: red, orange, yellow, and deep-green fruits and vegetables • Heat improves digestibility and absorption

38. 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

39. 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. 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 Vitamin A and Epithelial Tissue

43. 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. Vitamin A Requirements • 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

46. Vitamin A Requirements • Deficiency • Night blindness • Xerophthalmia • Hyperkeratosis • Impaired immunity, failure of normal growth Vitamin A and the Visual Cycle

48. 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