HS 331: The Role of Antioxidants
HS 331: The Role of Antioxidants HS 331
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This 5 page Class Notes was uploaded by Sydney Brummett on Thursday October 6, 2016. The Class Notes belongs to HS 331 at Wichita State University taught by Dr. Lisa Wray in Fall 2016. Since its upload, it has received 18 views. For similar materials see Principles of Diet and Nutrition in Health Sciences at Wichita State University.
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Date Created: 10/06/16
Chapter 8 Lecture: Nutrients Involved in Antioxidant Function and Vision • Structure of Atoms o Atom: the smallest unit of matter § Atoms are composed of • Nucleus – positively charged center portion of the atom • Electrons – negatively charged particles surrounding the nucleus • Oxidation o Molecules are composed of atoms o During metabolic reactions, electrons ban be transferred § From the atoms to one molecule § To the atoms of another molecule o Oxidation: the loss of electrons from a molecule o Reduction: the gain of electrons by a molecule o Oxidation and reduction usually occur together as an exchange reaction o Stable atoms contain an even number of paired electrons o Free radical: an atom that has lost an electron and is left with an unpaired electron § Highly reactive and can cause damage to molecules in the cell • Formation of free radicals o Many metabolic processes involve oxidation reactions and can produce free radicals § Free radicals are also produced by: • Pollution • Ultraviolet light and radiation • Toxic substances • Impact of free radicals o Free radicals cause damage to § Cell membranes § Low-density lipoproteins (LDLs) § Proteins in the cell § Genetic material (DNA) • Diseases linked to free radicals o Cancer o Heart disease o Type 2 diabetes o Arthritis o Cataracts o Alzheimer’s disease o Parkinson’s disease • Antioxidants o Free-radical formation is generally kept under control by antioxidant vitamins, minerals, and phytochemicals § Antioxidant vitamins donate electrons or hydrogen atoms to free radicals to stabilize them § Antioxidant minerals work within antioxidant enzyme systems that limit damage and destroy free radicals § Phytochemicals are plant chemicals that help stabilize free radicals and prevent damage • Vitamin E o Vitamin E is fat-soluble vitamin made of o Tocotrienol – biologically inactive form o Tocopherol – biologically active form • Functions of Vitamin E o Primary role is as an antioxidant o Protects polyunsaturated fatty acids (PUFAs) o Protects low-density lipoproteins (LDLs) o Recommended dietary allowance (RDA) is 15 mg alpha-tocopherol per day o Tolerable upper limit is 1,000 mg per day o Sources of vitamin E § Veggie oils, nuts, seeds, wheat germ, soybeans § Animal and dairy products are poor source o What if you consume too much vitamin E? § Some studies suggest possible links to vascular disease, diabetes, heart failure, and prostate cancer § Side effects such as nausea, intestinal distress, and diarrhea and have been reported § Vitamin E can interfere with anticoagulant medication o What if you don’t consume enough vitamin E? § Vitamin E deficiencies are uncommon § Can result in fragile red blood cells (erythrocyte hemolysis) § Can cause loss of muscle coordination and reflexes § Can impair immune function • Vitamin C o Vitamin C is a water-soluble vitamin that must be consume in the human diet o Functions of vitamin C: § Antioxidant § Synthesis of collagen § Prevents the disease scurvy § Enhances the immune system § Regenerated vitamin E after oxidation § Enhances the absorption of iron o Recommended intake § 90 mg/day for men; 75 mg/day for women § Smokers need an extra 35 mg/day § UL is 2,000 mg/day for adults o Sources of vitamin C § Fresh fruits and veggies § Heat destroys vitamin C § Cooking foods lowers their vitamin C content o What if you consume too much vitamin C? § Megadoses (ten times or more of the recommended intake) of vitamin C can cause nausea, diarrhea, nosebleeds, and abdominal cramps § Can cause iron toxicity in people with hemochromatosis § Can lead to kidney stone formation in people with kidney disease o What if you don’t consume enough vitamin C? § Scurvy is the most common vitamin C deficiency disease • Bleeding gums, loose teeth, wounds that fail to heal, swollen ankles and wrists, bone pain and fractures, diarrhea, weakness, and depression § Anemia can also result from vitamin C deficiency • Selenium o Selenium is a trace mineral found in a few amino acids in the body § Functions of selenium • Antioxidant – art of the glutathione peroxidase enzyme system • Production of thyroxine, a thyroid hormone o Recommended intake § 55 micro grams per day for men and women § UL is 400 micro grams per day o Sources of selenium § Rich sources include organ meats, pork, seafood, fish, and nuts o What if you consume too much? § Selenium toxicity (brittle hair, nails, skin rashes) can result from supplements o What if you don’t consume enough? § Keshan disease: a form of heart disease § Kashin-Beck disease: a type of arthritis • Copper, Iron, Zinc, and Manganese o Cofactor: a compound needed for proper functioning an enzyme § Copper, zinc, and manganese are cofactors for the superoxide dismutase antioxidant enzyme system § Copper, iron, and zinc help us maintain the health of our blood § Manganese is an important cofactor in carbohydrate metabolism • Beta-Carotene o Beta-carotene is: § In the class of chemicals called carotenoids § A provitamin: inactive precursors that must be converted to the active form of a vitamin in the body § The precursor or retinol, an active form of vitamin A o Functions of beta-carotene: § A relatively weak antioxidant § Effective against oxidation in cell membranes and LDLs o Carotenoids in general are known to: § Enhance the immune system § Protect skin from damage by UV light § Protect eyes from damage o Recommended intake: § Not considered an essential nutrient § No RDA has been established o Sources of beta-carotene: § Fruits and veggies are red, orange, yellow and deep green § Carotenoids are better absorbed from cooked foods o What if you consume too much? § Large quantities do not appear to be toxic § Skin may turn yellow or orange at high intakes; harmless and reversible o What if you don’t consume enough? § There are no known deficiency symptoms • Vitamin A o Vitamin A is a fat-soluble vitamin § Excess vitamin A is stored in the liver, adipose tissue, kidneys and lungs § There are three active forms of vitamin A • Retinol • Retinal • Retinoic acid o Functions of Vitamin A: § Contributes to cell differentiation § Contributes to reproduction and bone growth § May act as an antioxidant § Essential to sight o Recommended daily intake: § RDA is 900 micro grams per day for men, 700 micro grams per day for women o Sources of vitamin A: § Animal sources: liver, eggs § Plant sources such as the provitamin carotenoids (dark-green, orange, and deep-yellow fruits and veggies) o What if you consume too much? § Vitamin A is highly toxic, especially from supplements § Birth defects and permanent damage to the liver and eyes can result o What if you don’t consume enough? § Night blindness is the most common disease § Irreversible blindness (xerophthalmia) • In Depth: Cancer o Cancer: a group of related diseases characterized by cells growing out of control § Composed of three steps • Initiation – a cell’s DAN is mutated • Promotion – altered cell repeatedly divides • Progression – cells grow out of control o Factors that increase risk for cancer: § Family history of cancer § Tobacco use § Weight, poor diet, and sedentary lifestyle § Infectious agents (e.g., STDs) § Sun exposure (ultraviolet radiation) o Signs and symptoms of cancer § Unexplained weight loss § Fever § Extreme fatigue § Pain § Skin changes § Changes in bowl habits or bladder function § Indigestion or trouble swallowing § White patches inside the mouth or on the tongue § Unusual bleeding or discharge § Any thickening or lump § Nagging cough or hoarseness o Cancer treatments § Treatment varies according to the location, the ell type, whether or not it has metastasize, and other individual factors § Three major types of treatments: • Surgery • Radiation • Chemotherapy o Cancer prevention: § Check: get screenings and exams § Quit: stop smoking and alcohol abuse § Move: get regular physical activity § Nourish: maintain a recommended weight and eta a balanced, healthful diet o Role of Antioxidant in Cancer § Antioxidants may contribute to reducing the risk of cancer § Antioxidants may reduce cancer risk by: • Enhancing the immune system • Preventing oxidative damage to cells • Inhibiting the growth of cancer cells and tumors • Inhibiting the capacity of cancer cells to avoid again and programmed cell death (apoptosis)
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