Nutrients Involved in Antioxidant Function

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Nutrients Involved in Antioxidant Function
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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

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Exchange Reactions

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

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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
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What Causes Free Radicals?

• Metabolic processes
• Immune system fighting infections
• Environmental factors
• Pollution
• Excess sunlight
• Toxic substances
• Radiation
• Tobacco smoke
• Asbestos

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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

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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
• Alzheimers disease
• Parkinsons disease

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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

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Antioxidant Enzymes

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

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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

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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

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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

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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)

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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

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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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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

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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

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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

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Vitamin C and Its Functions

• Water soluble
• Functionssynthesis of
• Collagen (prevents scurvy)
• DNA
• Bile
• Neurotransmitters (serotonin)
• Carnitine (transports long-chain fatty acids)
• Hormones (thyroxine, epinephrine, steroids)

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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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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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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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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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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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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

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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

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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

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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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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

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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
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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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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

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Vitamin A Requirements

• Deficiency
• Night blindness
• Xerophthalmia
• Hyperkeratosis
• Impaired immunity, failure of normal growth

Vitamin A and the Visual Cycle
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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

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Selenium

• 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

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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

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Cancer

• A group of diseases characterized by cells
  growing out of control
• Tumors immature undifferentiated cell masses
  that have no physiologic function
• Malignant (cancerous) benign (harmless)
• Primary steps of cancer development
• Initiation
• Promotion
• Progression

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Cancer Risk

• Risk factors
• Tobacco use
• Unhealthful diet
• Infectious agents
• Ultraviolet radiation
• Physical inactivity

ABC Video Tobacco Addiction
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Cancer Risk

• Antioxidants prevent cancer
• Enhance immune system
• Inhibit cancer cell growth
• Prevent oxidative damage to cells

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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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Major Risk Factors for CVD

• Smoking
• Hypertension
• High blood levels of LDL cholesterol
• Obesity
• Sedentary lifestyle

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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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Low-Grade Inflammation

• More important than elevated cholesterol?
• Weakens plaque in blood vessels (more fragile)
• 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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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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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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Age-Related Vision Impairment

• Macular degeneration
• Leading cause of blindness
• Deterioration of center portion of retina
• Loss of the ability to see details
• Cataract
• Damaged portion of eyes lens (cloudy vision)
• Impaired adjustment from dark to bright light

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Age-Related Vision Impairment

• Possible role of antioxidants
• Supplements may reduce progression of macular
  degeneration
• Mixed results from cataract research
• Current research does not support the use of
  antioxidant supplements to prevent these two
  diseases of aging