Chapter 10 Nutrients Involved in Antioxidant Function What are Antioxidants and How Does the Body Use Them Compounds that protect cells from the damage caused by oxidation Oxidation Is a Chemical Reaction in Which Atoms Lose Electrons The loss of electrons is called oxidation because it s fueled by oxygen o Atoms are also capable of gaining electrons through reduction Stable atoms have an even number of electrons orbiting in pairs at successive distances from the nucleus o When an atom is left with an odd number of electrons in its outermost shell it s called an unpaired electron Two atoms with unpaired electrons immediately pair up making newly stabilized molecules In rare cases atoms with unpaired electrons in their outermost shell remain unpaired These are highly unstable and called free radicals The process of metabolism sometimes results in the release of a single electron and an oxygen atom will accept one of these single electrons This new unstable oxygen atom will become a free radical common during metabolism Environmental factors that cause free radical formation include exposure to pollution excessive sunlight toxic substances radiation tobacco smoke and asbestos Free Radicals Can Destabilize Other Molecules and Damage Cells Free radicals that form within the phospholipid bilayer of cell membranes steal electrons from their stable lipid molecules With the cell membrane s integrity lost the ability to regulate the movement of fluids and nutrients into and out of the cell is also lost Other sites of free radical damage include ldls proteins and dna o Damage to these sites increase the risk of heart disease various cancers diabetes cataracts Alzheimer s disease and Parkinson disease Antioxidants Work by Stabilizing Free Radicals or Opposing Oxidation Antioxidant vitamins work independently by donating their electrons or hydrogen molecules to free radicals to stabilize them and reduce the damage cause by oxidation The body fights free radicals and repairs damage by stabilizing free radicals or oppose oxidation Antioxidant minerals including selenium copper iron zinc and manganese act as cofactors within complex antioxidant enzyme systems that convert free radicals to less damaging substance that are excreted by the body o Superoxide dismutase converts free radicals to less damaging substances such as hydrogen peroxide o Catalase removes hydrogen peroxide from the body by converting it to water and oxygen o Glutathione peroxidase removes hydrogen peroxide from the body and stops the o dietary fats carry it from the intestines through the lymph syste man eventually production of free radicals in lipids A Profile of Nutrients That Function as Antioxidants Vitamin E fat soluble vitamin transport it to the cells o incorporated into the chylomicrons o transported to the liver o VLDL and released into the blood o Stored in the body s adipose tissue and cell membranes Forms of vitamin e o Tocotrienols and tocopherols o Tocopherol compounds are the biologically active forms Most active is alpha tocopherol Functions of vitamin e o Protects polyunsaturated fatty acids o Lowers the risk for heart disease o Protects ldls o Prevents oxidation and reduces rancidity and spoilage RDA Toxicity o 15 mg alpha tocopherol a day Prevents erythorocyte hemolysis rupturing of red blood cells o Tolerable intake is 1000mg Food sources o Safflower oil sunflower oil canola oil and soybean oil o Destroyed by oxygen UV light and heat o Really only susceptible in adults over 55 with vascular disease or diabetes with a daily intake of 268 mg or higher for 7 years resulted in heart failure o Side effects nausea intestinal distress and diarrhea o Certain medications react negatively with vitamin e Anticoagulants substances that stop blood clotting i e asprin Tylenol Coumadin hemorrhage Deficiency o Uncommon o Erythrocyte hemolysis rupturing of red blood cells lead to anemia o Include loss of muscle coordination and reflexes impairments in vision speech and movement o Immune function Vitamin C Water soluble Function o Consume on a regular basis o Preventing scury o Synthesis of collagen o Synthesis of dna bile neurotransmitters such a serotonin regulates mood and carnitine o Hormone o Protects ldl cholesterol from oxidation o Antioxidant in the lungs helping to protect from ozone and cigarette smoke o Protects white blood cells from the oxidative damage that occurs in response to fighting illness and infection RDA o 90 mg for men 75 for women o Upper intake level is 2000 mg o Smokers increase 35 mg o Other situations increase the need for vitamin c Traumatic injury surgery or burns Food sources o Fruits and vegetables o Heat and oxygen destroy vitamin c Boiling leaches Toxicity o Usually excrete any excess o Only supplements lead to toxicity Nausea diarrhea nosebleeds and abdominal cramps o Hemochromatosis excess accumulation of iron in the body Deficiency o Scurvy o Bleeding gums and joints loose teeth weakness hemorrhages around the hair follicles of the arms and legs wounds that fail to heal swollen ankles and wrists bone pain and fractures diarrhea and depression o Anemia Beta carotene Not considered an essential nutrient provitamin found in many fruits and vegetables Our bodies convert beta carotene to an active form of vitamin a or retinol o Beta carotene is a precursor of retinol Phytochemical classified as a carotenoid 12 g of beta carotene considered equivalent to 1 g of vitamin a o Sometimes a beta carotene molecule is cleaved in such a way that only one molecule of vitamin a is produced o Not all of the dietary beta carotene that is consumed is converted to vitamin a and the absorption of beta carotene from the intestines is not as efficient as our absorption of vitamin a o Retinol activity equivalents Functions o Harmful effects of oxidation in the lipid portions of the cell membranes and in ldls Relatively weak antioxidants o Enhance immune system and boost the body s ability to fight illness and disease o Protect skin from the damage caused by the sun s ultraviolet rays o Protect our eyes preventing or delaying age related vision impairment RDA Food sources o No rda has been established o 6 10 mg has shown to reduce the risks of some disease o Fruits and vegetables that are red orange yellow and deep green Lutein and lycopene o Carotenoids are absorbed better from cooked foods Toxicity o Carotenosis or carotenodermia Skin turns yellow or orange reversible and harmless Vitamin A Much More Than
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