1. Chapter 10: Nutrients Involved in Antioxidant Function and Vision
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2. What Are Antioxidants?
Compounds that protect cells from the damage caused by oxidation
Hence, "anti"-oxidation
Some nutrients with antioxidant properties:
Vitamin E
Vitamin C
Vitamin A (precursor beta-carotene)
Selenium
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3. Exchange Reactions
Oxidation is a chemical reaction in which atoms lose electrons
Reduction occurs when atoms gain an electron
Oxidation-reduction reactions typically result in an even exchange of electrons, called exchange reactions.
Exchange reactions consists of 2 parts. (a) During oxidation, molecules lose electrons. (b) In the second part of the reaction, molecules gain electrons, which is called reduction.
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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
When an oxygen molecule becomes a free radical, it is specifically referred to as a reactive oxygen species (ROS).
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7. What Causes Free Radicals?
Metabolic processes
Ex: immune system fighting infections
Environmental factors
Pollution
Excess sunlight
Toxic substances
Radiation
Tobacco smoke
Asbestos
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8. 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
Cell membrane is unable to regulate the movements of fluids and nutrients into and out of the cell. This loss of cell integrity causes damage to the cell and to all systems affected by this cell. Free radicals damage cell membranes, low-density lipoproteins (LDLs), cell proteins, and DNA.
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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
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11. 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 and prevent damage to cells and tissues
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12. Antioxidant Enzymes Antioxidant enzymes/enzyme systems:
Convert free radicals to less damaging substances
Break down oxidized fatty acids that have become oxidized
Make more vitamin antioxidants available to fight other free radicals
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13. Antioxidant Enzymes (continued)
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
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14. 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
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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) and is a part of low-density lipoproteins (LDLs)
90% of vitamin E is stored in adipose tissue, the rest in cell membranes
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17. Forms of Vitamin E
Two families of compounds: tocotrienols and tocopherols.
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 and International Units (IU)
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19. Functions of Vitamin E
Protects polyunsaturated fatty acids (PUFAs), fatty cell components, and LDLs from oxidization (lower heart disease risk)
Protects red blood cell membranes and lung cells
Anticoagulant properties, opposes excessive clot formation
Normal nerve and muscle development in early life
Enhances immune system
Improves vitamin A absorption, if intake is low
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20. 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
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21. Food Sources of Vitamin E
Vitamin E is widespread in plant-based foods
Vegetable oils (safflower, sunflower, canola, soybean), mayonnaise, salad dressing
Nuts, seeds, soybeans, avocado
Vitamin E is destroyed by exposure to oxygen, metals, ultraviolet light, and heat
Heating oils destroys vitamin E, fried, processed, and fast foods contain little vitamin E
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23. Vitamin E Toxicity
High supplemental doses of vitamin E may be harmful for certain individuals with vascular disease
Side effects: nausea, intestinal distress, and diarrhea
Interacts with anticoagulants (aspirin, Coumadin)
Long-term use may cause hemorrhagic stroke
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24. Vitamin E Deficiency
Deficiency is uncommon in humans, since vitamin E is stored in fatty tissues
Associated with fat malabsorption
Symptom of deficiency: Erythrocyte hemolysis (rupturing of red blood cells) leads to anemia
Symptoms: loss of muscle coordination and reflexes; impaired vision, speech
Impaired immunity (with low selenium)
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25. Vitamin C and Its Functions
Water soluble
Two active forms: ascorbic acid and dehydroascorbic acid
Functions—synthesis of:
Collagen (prevents scurvy)
DNA
Bile
Neurotransmitters (serotonin)
Carnitine (transports long-chain fatty acids)
Hormones (thyroxine, epinephrine, steroids)
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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
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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
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30. 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
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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)
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33. 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
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34. Antioxidant Minerals Systems: Selenium
Trace mineral needed in small amounts
Majority contained in amino acid derivatives:
Selenomethionine: storage form
Selenocysteine: active form, part of glutathione peroxidase enzyme system
Spares vitamin E
Needed for thyroxine (thyroid hormone) production: basal metabolism, body temperature
Poor status associated with cancer
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36. Selenium Requirements
Trace amounts to maintain health
RDA: 55 µg/day
UL: 400 µg/day
Sources: organ meats, pork, seafood
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38. 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 (impaired immunity to fight disease-causing virus)
Kashin-Beck disease, deforming arthritis
Infertility, depression, impaired cognitive function, muscle pain and wasting
Cretinism (with iodine deficiency)
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39. Kashin-Beck disease creates deforming arthritis.
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40. Other Minerals Assist in Antioxidant Function
Copper, zinc, and manganese are part of the superoxide dismutase enzyme antioxidant complex
Iron is part of the catalase structure
Manganese: important cofactor in macronutrient metabolism
Copper, iron, and zinc for blood health
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41. Beta-Carotene Phytochemical classified as a carotenoid
Provitamin, inactive form that cannot be used until converted to active form (precursor of retinol)
Expressed in food as Retinol Activity Equivalents (RAE), which indicates how much active vitamin A is available to the body after conversion
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43. Functions of Beta-Carotene
Weak antioxidant compared to Vitamin E
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
Diet rich in carotenoids associated with decreased cancer risk
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44. Beta-Carotene Requirements
Beta-carotene is not an essential nutrient, no RDA established
Food sources: red, orange, yellow, and deep-green fruits and vegetables
Better absorbed from cooked foods
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46. 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
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47. Vitamin A Fat soluble Active forms: retinol, retinal, retinoic acid
Stored mainly in the liver
Retinol-binding protein transports retinol
Expressed as Retinol Activity Equivalents (RAE)
International Units (IU) for vitamin A on food labels or dietary supplements
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50. Vitamin A Essential for healthy vision
Cell differentiation, process by which stem cells mature into specialized cells
Differentiates immune cells (T cells) to assist in fighting infection
Sperm production and fertilization
Healthy bone growth
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51. 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)
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53. 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
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54. Vitamin A Requirements
Deficiency less common in developed countries, is a severe public health concern in developing countries
Deficiency can result in:
Night blindness
Xerophthalmia: blindness due to cornea hardening
Hyperkeratosis: excess keratin in hair follicles
Impaired immunity, failure of normal growth
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56. 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)
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57. Disorders Related to Free-Radicals: Cancer
Primary steps of cancer development:
Initiation
Promotion
Progression
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59. 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
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61. Human papillomavirus (HPV).
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62. A malignant melanoma lesion.
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63. 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
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64. 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
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65. Major Risk Factors for CVD
Smoking
Hypertension
High blood levels of LDL cholesterol
Obesity
Sedentary lifestyle
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66. 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
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67. 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
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68. 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
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69. 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
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