Chapter 10: Nutrients Involved in Antioxidant FunctionWhat are Antioxidants, and How Does the Body Use Them?- Compounds that protect cells from the damage caused by oxidationOxidation Is a Chemical Reaction in Which Atoms Lose Electrons- The loss of electrons is called oxidation because it’s fueled by oxygeno 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 nucleuso 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 dnao 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 bodyo Superoxide dismutase: converts free radicals to less damaging substances, such as hydrogen peroxideo Catalase removes hydrogen peroxide from the body by converting it to water and oxygeno Glutathione peroxidase: removes hydrogen peroxide from the body and stops the production of free radicals in lipidsA Profile of Nutrients That Function as AntioxidantsVitamin E- fat soluble vitamino dietary fats carry it from the intestines through the lymph syste man eventually transport it to the cellso incorporated into the chylomicronso transported to the livero VLDL and released into the bloodo Stored in the body’s adipose tissue and cell membranes- Forms of vitamin eo Tocotrienols and tocopherolso Tocopherol compounds are the biologically active forms Most active is alpha-tocopherol - Functions of vitamin eo Protects polyunsaturated fatty acidso Lowers the risk for heart diseaseo Protects ldlso Prevents oxidation and reduces rancidity and spoilage - RDA o 15 mg alpha-tocopherol a day Prevents erythorocyte hemolysis: rupturing of red blood cellso Tolerable intake is 1000mg - Food sourceso Safflower oil, sunflower oil, canola oil, and soybean oilo Destroyed by oxygen, UV light, and heat - Toxicityo 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 failureo Side effects: nausea, intestinal distress, and diarrheao Certain medications react negatively with vitamin e Anticoagulants: substances that stop blood clotting i.e. asprin, Tylenol - Coumadin hemorrhage- Deficiencyo Uncommono 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 functionVitamin C- Water solubleo Consume on a regular basis - Functiono Preventing scuryo Synthesis of collageno Synthesis of dna, bile, neurotransmitters such a serotonin (regulates mood), and carnitineo Hormoneo Protects ldl cholesterol from oxidationo Antioxidant in the lungs helping to protect from ozone and cigarette smokeo Protects white blood cells from the oxidative damage that occurs in response to fighting illness and infection- RDAo 90 mg for men 75 for womeno 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 sourceso Fruits and vegetableso Heat and oxygen destroy vitamin c Boiling leaches - Toxicityo Usually excrete any excess o Only supplements lead to toxicity Nausea, diarrhea, nosebleeds, and abdominal crampso 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 depressiono 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 retinolo 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 producedo 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 ao Retinol activity equivalents- Functionso Harmful effects of oxidation in the lipid portions of the cell membranes and in ldls Relatively weak antioxidantso Enhance immune system and boost the body’s ability to fight illness and diseaseo Protect skin from the damage caused by the sun’s ultraviolet rayso Protect our eyes, preventing or delaying age-related vision impairment- RDAo No rda has been establishedo 6-10 mg has shown to reduce the risks of some disease- Food sourceso Fruits and vegetables that are red, orange, yellow, and deep green Lutein and lycopeneo Carotenoids are absorbed better from cooked foods- Toxicityo
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