Antioxidants Week 10 - Copy PDF

z ANTIOXIDANTS Week 10 – Chapter 12 z Vitamins § Considered micronutrients § Organic compounds vital to life § Indispensable to body functions § Needed in small amounts § Non-caloric essential nutrients § Fat OR Water soluble § Precursors/Provitamins...

z ANTIOXIDANTS Week 10 – Chapter 12 z Vitamins § Considered micronutrients § Organic compounds vital to life § Indispensable to body functions § Needed in small amounts § Non-caloric essential nutrients § Fat OR Water soluble § Precursors/Provitamins § Compounds in food converted to active vitamins z Fat Soluble Vitamins Vitamins A, D, E, K § Absorbed into the lymph, travel in the blood in association with protein carriers § Dissolve in lipid § Require bile for absorption § Stored in the liver & body tissues § May be toxic in excess from supplements (A,D,K) § Deficiencies occur with low intake or fat malabsorption z Water Soluble Vitamins B vitamins and vitamin C § Dissolve in water – cooking & washing with water can leach them out of foods § Easily absorbed into the bloodstream & excesses excreted in the urine § Not stored extensively in body tissues § Seldom reach toxic levels (high doses of supplements = expensive urine)  z Antioxidants Oxidation: § Part of normal metabolism and occurs when atoms lose electrons § As molecules breakdown, they reform new bonds to make new stable compounds….however…. § If an atom with an electron that is not paired with a new one, it becomes highly unstable and reactive Free radicals § Have unpaired electrons in outer orbital = unstable § Can lead to damage of cells and their functions § Accumulation can lead to oxidative stress z What Nutrients are Antioxidants? Fat Soluble Vitamins: § Vitamin A (including beta-carotene) § Vitamin E Water Soluble Vitamin: § Vitamin C Trace Mineral: § Selenium z Role Of Antioxidants § Protect cells from oxidative damage § Vitamin antioxidants (A,C,E) - Donate electrons to free radicals to prevent cell damage § Trace mineral Antioxidant (Se) – are cofactors of enzyme systems that have protective effects § Prevent creation of new free radicals z z Vitamin A & Beta-Carotene Three active forms in the body: § Retinol (alcohol form) § Most active form § Retinal (aldehyde form) § Retinoic acid (acid form) § converted by cells from retinol § Plant-derived precursor – Beta-carotene z Food Sources: § Animal foods § Contain retinoids (retinol, retinal, retinoic acid) § Provided as retinyl esters that are easily digested and absorbed as retinol in the SI § Plant-based foods § Provide carotenoids § Beta-carotene – can be converted to vitamin A in the SI and liver § Conversion and absorption is much less than retinoids § Deep orange fruits & dark green leafy vegetables § sweet potatoes, carrots, spinach, Bok choy, broccoli, apricots, mango, cantaloupe z Digestion/Absorption/Transportation: § Digested and absorbed by several proteins § Absorbed via lymph system § Stored in liver Retinol-Binding Protein (RBP): § Picks up vitamin A from the liver and transports it to cells § Cells have RBP receptors § Action within cells may vary depending on receptor § Retinoic acid stimulates cell growth in skin § Retinoic acid inhibits cell growth in tumours z Roles of Vitamin A 1. Vision § Maintains crystal clear outer window – the cornea § Covering outside of the eye § Conversion of light energy to nerve impulses at the retina § Some photosensitive cells of the retina contain rhodopsin (pigment) § Rhodopsin = protein Opsin + retinal z § Process: § Light passes through cornea à retina à rhodopsin responds by releasing opsin § Retinal shifts from CIS to TRANS configuration to generate electrical impulses conveying messages to the brain § Much of the retinal shifts back to active CIS formation, combined with opsin to reform rhodopsin § Some retinal oxidized to retinoic acid à dead end for the visual process § Requires constant replenishment of retinal from foods or retinol stores z Roles of Vitamin A 2. Protein Synthesis & Cell Differentiation: § Cell differentiation § Each cell develops to perform a specific function § Goblet cells – synthesize and secrete mucous § Maintains integrity of epithelial tissues § Outer = skin § Inner = mucous membranes that line the GI tract, lungs, eyelids etc. § Protects from damage of microorganisms and substances including gastric juices  z Roles of Vitamin A 3. Reproduction & Growth: § Males § Retinol and sperm development § Women § Fetal development § Children lacking vitamin A have poor growth § Bone remodeling: § Necessary for bone growth § Vitamin A participates in dismantling – enzymes help to break remove parts that are not needed § Bone dismantling cells (osteoclasts) die, leaving a site for bone-building cells (osteoblasts) to promote growth z Roles of Vitamin A 4. Antioxidant § Beta-carotene is a precursor for vitamin A § Acts as an antioxidant along with Vitamin C, E and Selenium  z Vitamin A Deficiency – hypovitaminosis A § Vitamin A status depends on: § Adequacy of vitamin A stores § Protein status § Retinol-binding protein (RBP) is the vitamin’s carrier within the body § Deficiency won’t occur until vitamin A stores are depleted, even when intake becomes inadequate § Symptoms would take awhile to develop for healthy adult, much sooner for a growing child § Common problem in developing countries § Food fortification or supplementation can prevent z Complications of Vitamin A Deficiency Infectious Diseases: § Inhibits replication of measles virus § In developing countries, severity of illness correlates with degree of vitamin A deficiency § Provision of vitamin A to child with measles can reduce risk of death by 50% § WHO and UNICEF: recommend two doses of Vitamin A supplement given 24h apart for all children with measles  z Complications of Vitamin A Deficiency Night Blindness: § One of first signs of vitamin A deficiency § lack of vitamin A at the back of the eye (retina) § Retina does not receive adequate retinal to regenerate pigments that are bleached by light § Limited ability to see after a flash of light or after dark § Corrected with vitamin A supplementation  z Complications of Vitamin A Deficiency Blindness (Xerophthalmia) § Total loss of vision § Lack of vitamin A at the front of the eye (cornea) § Severe vitamin A deficiency is the leading, preventable cause § Requires prompt vitamin A intervention § Develops in stages: 1. Xerosis: Decreased mucous productions causes the cornea to become dry and hard 2. Progresses to keratomalacia; softening of the cornea 3. Irreversible blindness z Complications of Vitamin A Deficiency Keratinization § Skin = dry, rough, scaly as keratin accumulates § Keratin - hard, inflexible protein found in hair/nails Gastrointestinal Tract § Decrease number and activity of goblet cells § Decrease digestion/absorption of nutrients  z Vitamin A Toxicity – hypervitaminosis A § Symptoms develop when all binding proteins are loaded § Excess vitamin A free to damage cells § Not likely when diet is balanced § Children at higher risk § Beta-carotene: § From food, not as likely to lead to toxicity § Not efficiently converted to vitamin A, stored in fat under the skin (may cause skin to turn yellow) § From supplements à may be harmful, acts as a pro-oxidant  z Vitamin A Toxicity Bone Defects: § Chronic excess intake may contribute to osteoporosis Birth Defects: § Spina bifida and cleft palate § Excess supplementation before 7th week of pregnancy is most harmful and supplements usually not given in first trimester Acne: § Large doses do not have an impact on acne Acute Toxicity Symptoms: § Nausea, vomiting, blurred vision, headaches, lack of muscle coordination z Vitamin A Recommendations § RDA: § Women: 700 ug RAE/day § Me: 900 ug RAE/day § Expressed as retinol activity equivalents (RAE) § You will note the DRI’s have a RDA/AI for vitamin A listed as both micrograms (ug) and international units (IU) § 1 IU retinol = 0.3 ug retinol or 0.3 ug RAE § UL for adults: § 3000 ug § Only applies to preformed vitamin A  z Vitamin A in Foods § Foods from animals § Contain retinoids § Liver, fish, oils, milk, butter, eggs § Milk with lower %MF is fortified with vitamin A § Plant based foods § Contain carotenoids (precursor for vitamin A) § Yellow and red pigment in plants § Bioavailability depends on fat content of the meal § Salad + salad dressing (regular vs fat free) z Vitamin A in Foods Colour of the food: § Dark, leafy greens and deep yellow/orange fruits and vegetables contain highest amounts § Squash, canteloupe, carrots – not corn or bananas § Spinach – not celery § Chlorophyll à green pigment of plants, absorbs light and transfers energy (initiates photosynthesis) § Beets and corn – although bright in colour, derive this from xanthophylls and have lower levels of vitamin A activity z Vitamin E: Role as an Antioxidant § Defends body against oxidative damage from free radicals § Prevents chain reactions leading to production of more free radicals § Protects vulnerable components of cells and their membrane from destruction § Prevents oxidation of polyunsaturated fatty acids (PUFAs) § May reduce risk of heart disease § Preventing oxidation of LDL § Reducing inflammation  z Vitamin E Deficiency § Primary deficiency from poor dietary intake is rare § May occur for those who consume diets very low in fat, consume highly processed foods for many years § Deficiency associated with diseases that impact fat absorption § Cystic fibrosis § Disease or injury to the liver, gallbladder, pancreas § Deficiency results in erythrocyte hemolysis - rupture of RBC causing spilling of their contents and anemia § r/t oxidation of PUFAs in cell membrane § Seen in premature infants before transfer of vitamin E from mother § Corrected with vitamin E treatment § Symptoms: prolonged deficiency can lead to neuromuscular dysfunction, impaired vision and speech (adults) § Corrected with vitamin E treatment  z Vitamin E Toxicity § Increase use of vitamin E supplements over the last several years with recognition of its protective properties against against chronic disease § Toxicity is rare § Interaction with Vitamin K § At extremely high doses § Enhance effects of drugs used to prevent blood clotting (anti- coagulants) § May result in hemorrhage § Ongoing research needed if linked to increased risk of hemorrhagic stroke  z Vitamin E Recommendations & Food Sources § RDA § 15mg/day (adults) § UL § 1000mg/day (adults) § Food Sources: § Majority comes from vegetable oils and those foods made from these § Seeds and nuts § Limited amount in processed foods due to destruction from heat processing  z Vitamin C § Other term - Ascorbic acid § Scurvy § Vitamin C deficiency prevalent many years ago among sailors who went on long voyages § Fruits/vegetables often used up within first few days § Nutrition experiment in the 1700s § Revealed those who received citrus juice intervention recovered quickly from scurvy § This then became standard practice  z Roles of Vitamin C § Antioxidant: § In body cells and fluids § Can lose electrons easily, therefore neutralizes free radicals § Can easily take electrons back to become active again § Enhances absorption of Fe and protects it from oxidation § Cofactor in Collagen formation: § Helps form collagen which plays many roles in the body § Bone and teeth formation § Cell formation § Scar formation  z Roles of Vitamin C § Cofactor in other reactions: § Helps in hydroxylation of carnitine § Participates in conversion to make neurotransmitters: § Tryptophan à serotonin § Tyrosine à norepinephrine § Assist in production of hormones § Thyroxine (regulates BMR) § Stress: § Increase vitamin C needs: burns, extreme temperatures, infections, some medications, smoking § Adrenal glands release vitamin C and hormones into the blood during stress  z Roles of Vitamin C § The Common Cold: § Research is conflicting § May reduce likelihood of getting a cold, decrease duration if taking large amounts of vitamin C § Can deactivate histamine z Vitamin C Recommendations § RDA: § 90mg /day men § 75mg /day women § 10mg/day to prevent scurvy § ~100mg/day provides tissue saturation § ~200mg/day max absorption – any additional excreted as it is not stored in tissues § Increased needs for smokers (~135mg/d) § UL § 2000mg/day  z Vitamin C Deficiency § Scurvy § Mouth: bleeding gums, loosened teeth § Microcytic anemia, § Bone fragility, joint pain § Atherosclerotic plaques § Immunity: increased infections, poor wound healing § Muscle: degeneration, pain § Skin: rough, blotchy, easily bruises, pinpoint hemorrhages  z Vitamin C Toxicity § GI upset – d/t excessive supplementation § Excess vitamin C in urine could interfere with some medical tests (Dx of diabetes) § Increase in supplement use may counteract some medications (those used to prevent blood clotting) § Kidney disease – may increase risk of kidney stone formation § Adverse effects associated with iron overload  z Food Sources of Vitamin C § Citrus fruits § Cabbage-type vegetables § Dark green vegetables § Berries § Tomatoes § Bell peppers § Cantaloupe § Mango, papaya z Roles of Selenium Antioxidant: § Works with vitamin E § Works as a part of proteins (enzyme Glutathione peroxidase) to prevent free radical formation § As part of other enzymes that activate or deactivate thyroid hormone (role in BMR) z Selenium Deficiency § Not very common § Associated with Keshan Disease § A type of heart disease § Prevalent in parts of China where soil and food lack selenium § Prevented by adequate selenium intake z Recommendations & Sources § RDA § Adults: 55ug/day § UL § 400ug/day § Food sources: § Meat, milk and eggs § Fruit ,vegetables and grains (levels depend on soil they are grown in) z Selenium Toxicity § High doses can be toxic, therefore UL has been set § Loss and brittleness of hair and nails § Garlic breath odour § Nervous system abnormalities § Fatigue, irritability z HIGHLIGHT 12: Antioxidant Nutrients: What is Their Role in Disease Prevention? z Free Radicals & Disease Free radical: an unstable molecule with one or more unpaired electrons, highly reactive § steals an electron from another molecule, that molecule now becomes unstable and a free radical § Other than normal body processes, free radicals can come from UV radiation, air pollution, and tobacco smoke Antioxidants: donate an electron to neutralize the free radicals § Do not become free radicals after donating because they are stable in either form z  z Defending Against Free Radicals § System of enzymes disarms most harmful oxidants § This is dependent upon adequate amounts of selenium, copper, manganese, iron and zinc § Inadequate dietary intake = weakened defense § Antioxidant vitamins: § Vitamin Eà defends body’s lipids by stopping free radical chain reaction § Beta-carotene à acts in lipid membranes § Vitamin C à protects the skin and blood. Restores oxidized vitamin E to it’s active state z Defending Against Cancer § Cancer results from damage to cellular DNA § Antioxidants may protect DNA from this oxidative damage § Research has linked certain antioxidants with different types of cancers § Research supports a diet rich in fruits and vegetables containing antioxidants linked to benefits  z Defending Against Heart Disease Vitamin E § May protect against HTN and CVD § Defends against LDL oxidation, inflammation, arterial injuries and blood clotting § Caution for high doses of supplements, as this may have adverse effects Vitamin C § Protects against LDL oxidation, raises HDL, lowers total cholesterol and improves BP § Role of vitamin C supplementation remains uncertain Selenium § Further research is needed on the role of selenium and heart disease  Foods vs Supplements z ….and chronic disease z MID-TERM #2 INFO: Date: Tuesday November 5, 2024 (during lecture) Time: Please arrive by 6:45, please wait in the hall outside the classroom until you are called in. The exam will start at 7:00pm. Duration: 50minutes Format: multiple-choice (~35 questions) What to bring: pencil, non-programmable calculator z Library Session: Asynchronous online This will be posted by Tuesday November 12, 2024 § Please review at your own pace this week § You are responsible for the content of this lecture Library Quiz: § Worth 5% of your final grade § Available online via BrightSpace Thursday November 14, 2024 at 5:00pm and will be open until Thursday November 21, 2024 at 11:59pm. § This is not timed, you will have one attempt