1 / 70

Nutrients Involved in Antioxidant Function

10. Nutrients Involved in Antioxidant Function. 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. Exchange Reactions.

flynn
Download Presentation

Nutrients Involved in Antioxidant Function

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  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

  4. 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

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

  6. 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

  7. 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

  8. 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

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

  10. 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

  11. 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

  12. 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

  13. 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)

  14. 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

  15. 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

  16. 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

  17. 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

  18. 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

  19. 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)

  20. 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

  21. 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

  22. 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

  23. 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)

  24. 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

  25. 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

  26. 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

  27. 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

  28. 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

  29. 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

  30. 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

  31. 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)

  32. 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

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

  34. 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

More Related