NTR 109 - Lecture #5

NTR 109 - Lecture #5 - Vitamins& Phytochemicals Fun...

Info icon This preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Vitamins & Phytochemicals Fun Facts Vitamins were named in order of discovery (A, B, C, D, ...) Other substances found not to be essential were dropped (ex., vitamin P) Bvitamins were thought to be one vitamin; turned out to be many (ex., B1, B2, B3, ...) Scientists believe they have discovered all the vitamins Vitamins Essential organic substances Produce deficiency symptoms when missing from diet Yield no energy Basic functions Fatsoluble vitamins Facilitate energyyielding chemical reactions Function as coenzymes Watersoluble vitamins Types of Vitamins Provitamin precursor; compound that can be converted into an active vitamin 2 General Classes: Fat soluble: vitamin A vitamin D vitamin E vitamin K 2) 1) Bvitamins Thiamin (B1) Niacin (B3) Biotin vitamin B12 Water soluble: Riboflavin (B2) vitamin B6 Folate vitamin C Pantothenic acid Storage of FatSoluble Vitamins Fatsoluble Absorbed with fat Stored in large amounts More time needed to become deficient Not readily excreted (except vitamin K) Highly toxic especially vitamins D and A Storage of WaterSoluble Vitamins Watersoluble vitamins Stored in small amounts Less toxic (usually) High doses are generally lost from the body (except vitamins B6 and B12) excreted via urine Takes less time for deficiency to develop (due to limited storage) Some can cause toxicity Mostly likely due to supplementation Preservation of Vitamins Decreased vitamin content Eat foods soon after harvest Freeze foods not consumed within a few days Blanching destroys enzymes Improper storage Excessive cooking Exposure to light, heat, air, water and alkalinity Slows down vitamin degradation FatSoluble Vitamins Overview Dissolve in organic solvents Not readily excreted Absorbed along with fat Fat malabsorption Can cause toxicity Transported with fat May cause deficiency In lipoproteins Vitamin A Narrow optimal intake range Preformed Retinoids (retinol, retinal, retinoic acid) Found in animal products Proformed Carotenoids Found in plant products Functions of Vitamin A Promote vision Promote growth Prevent drying of the skin and eyes Classic deficiency: Night blindness Promote immune function and resistance to bacterial infection (plays a role in the production of WBC's) Acne medication Xerophthalmia leading cause of blindness in 3rd world countries due to lack of vitaminA rich foods Vitamin A and Vision Functions in light perception at the retina Maintains health of cornea to keep it crystal clear Deficiencies lead to: vitamin A is a part of rhodopsin, a pigment found in the retina, which, upon activation by light, signals the optic center in the brain, giving us the sensation of sight Nightblindness: a lag in recovery of sight in darkness after a flash of bright light or Keratinization: of the eye, xerosis (corneal drying), triangular gray spots on eye (Bitot's spots), or xerophthalmia (corneal degeneration and blindness) Deficiency Symptoms Food Sources of Vitamin A Active vitamin A found in foods of animal origin such as liver, fish oil, milk, milk products, fortified cereals, butter, eggs Betacarotene is an orange pigment found in plant foods; it is found in fruits & vegetables with a deep orange color or dark, green color (pumpkin, sweet potatoes, carrots, cantaloupe, spinach, broccoli) 12 micrograms betacarotene = 1 microgram retinol Food Sources of Vitamin A Toxicity of Vitamin A Large intake of vitamin A (preformed) Signs and symptoms: Over a long period of time, especially in supplements Use of Accutane and RetinA Bone/muscle pain, loss of appetite, skin disorders, headache, dry skin, hair loss, increased liver size, vomiting Fetal malformation Possible permanent damage Effects of high carotenoid intake Vitamin D Prohormone works like a hormone, sends signals to organs Derived from cholesterol Synthesized from sun exposure Sunscreen SPF > 8 decreases synthesis 95% Expose hands, face, arms 23 x/week for 510 minutes each time (more for darker skin) Insufficient sun exposure makes this a vitamin you must get through regular dietary sources Activation of Vitamin D Vitamin D Liver 25hydroxyvitamin D Kidneys 1,25dihydroxyvitamin D (active hormone) Functions of Vitamin D Regulates blood calcium Along with parathyroid hormone Regulates calcium + phosphorus absorption in the gut, kidney and bone Reduces kidney excretion of calcium Regulates calcium deposition in bones Influences normal cell development Linked to reduction of breast, colon, and prostate cancer Role in Bone Formation Causes calcium + phosphorus to deposit in the bones Strengthens bones Vitamin D Deficiency Rickets is the result of low vitamin D Breastfed infants with little sun exposure Osteomalacia (soft bones) Ricketslike disease in adults Bones lose minerals and become porous Groups at Risk Elderly Ill Homebound Those with limited sun exposure and poor intake of vitaminD rich foods Food Sources of Vitamin D Fatty fish (salmon, herring) Fortified milk Some fortified cereals Margarine Eggs Toxicity Warning vitamin D can be very toxic, especially in infancy and childhood Upper Level is 50 ug/day Results in: Overabsorption of calcium (hypercalcemia); increased calcium excretion Calcium deposits in organs and blood vessels Growth retardation in children Vitamin E Also known as tocopherol Fatsoluble vitamin that functions as an antioxidant; also in nerve development & immunity, and may defend against heart disease Resides mostly on cell membranes Protects PUFA and cell membranes from oxidative stress, as well as other lipids and vitamin A, especially tissues exposed to high oxygen concentrations (ex. Lungs) Protects WBC; may improve immune response Other Functions of Vitamin E Protects double bonds in unsaturated fats Improves vitamin A absorption Deficiency Breakdown of cell membranes Hemolysis Nerve degeneration Food Sources of Vitamin E Toxicity of Vitamin E Upper Level is 1,000 mg/day (supplementary alphatocopherol) Upper Level is 1500 IU (natural sources) or 1100 IU (synthetic forms) Toxic effects: Inhibits vitamin K metabolism and anticoagulants Possible hemorrhage Muscle weakness, headaches, nausea Vitamin K ("Koagulation") Synthesized by bacteria in the colon and absorbed Role in coagulation process Role in calciumbinding potential Food Sources of Vitamin K Liver Green leafy vegetables Broccoli Peas Green beans Resistant to cooking losses Limited vitamin K storage in the body Adequate Intake for Vitamin K Excess vitamin A and E Newborns Interferes with vitamin K May cause hemorrhage and fractures Routinely injected with vitamin K; is required by newborns due to their lack of intestinal bacteria Breast milk is a poor source Toxicity unlikely; readily excreted Dissolve in water Overview of WaterSoluble Vitamins Generally readily excreted from body Subject to cooking losses Function as coenzymes Participate in energy metabolism 5090% of B vitamins are absorbed Marginal deficiency more common Enrichment Act The Bvitamins Function as coenzymes small molecules that combine with enzymes to activate them Enzymes cannot function without their coenzymes Coenzymes are often found at the active site of the enzyme (where the chemical reaction takes place), inducing a conformational change in the enzyme, thereby allowing substrate binding Do not yield energy themselves, but function in tissues throughout the body in the metabolism of the energyyielding nutrients Deficiencies of single B vitamins are rare; if deficient in one, usually deficient in others Coenzymes Thiamin (B1) Sensitive to alkalinity and heat Coenzyme form used in energy metabolism Classic deficiency syndrome: Beriberi Surplus is rapidly lost in urine; non toxic Food Sources of Thiamin Riboflavin (B2) Coenzyme forms participate in energyyielding metabolic pathways Deficiency Nontoxic Cheilosis, inflammation of mouth and tongue Cheilosis Food Sources of Riboflavin Milk/milk products Enriched grains/cereals Eggs Liver Spinach Oysters Brewer's yeast Niacin (B3) Coenzyme forms used in energy metabolism Can be made in the body from the amino acid tryptophan Classic deficiency Pellagra Symptoms include the 4 D's: diarrhea, dermatitis, dementia and death Toxicity Upper Level is 35 mg/day Niacin used pharmacologically to treat CVD can cause "niacin flush" results from very large doses Food Sources of Niacin Enriched grains Beef Chicken/turkey Fish Heat stable; little cooking loss Niacin equivalents Used to measure the amount of niacin in the diet; accounts for niacin from it's precursor, tryptophan 60 mg tryptophan can be converted into 1 mg niacin Pantothenic Acid Part of CoenzymeA Essential for metabolism of carbohydrate, fat, and protein A deficiency is rare Usually in combination with other deficiencies Food Sources of Pantothenic Acid Meat Milk Mushrooms Liver Peanuts Biotin Free and bound form Coenzyme Deficiency is also rare Metabolism of carbohydrate and fat Helps breakdown certain amino acids Food Sources of Biotin Cauliflower, egg yolk, liver, peanuts, cheese Intestinal synthesis of biotin contributes very little Avidin inhibits absorption Need to consume more than a dozen raw egg whites a day to cause this effect Cooking eggs denatures this protein Biotin Needs No Upper Level for biotin Relatively nontoxic Vitamin B6 Coenzyme forms Body's requirement for vitamin B6 is Activate enzymes needed for metabolism of carbohydrate, fat and protein Synthesize nonessential amino acids via transamination (aids in the conversion of tryptophan niacin) proportional to protein intake (athletes may need more) Food Sources of Vitamin B6 Vitamin B6 as a Medicine? 50100 mg/day therapy Carpal tunnel syndrome Morning sickness Toxicity potential Questionable treatment of PMS May treat pregnancy hypertension (100 mg/day may help; see Ch. 13) > 200 mg/day can lead to irreversible nerve damage Upper Level set at 100 mg/day Folate Coenzyme DNA synthesis Homocysteine metabolism Neurotransmitter formation Sensitive to: Heat, oxidation, ultraviolet light Folate and DNA Needed for DNA replication important for cell division Especially important for rapidly dividing cells such as RBC, WBC & cells of the digestive tract Deficiency results in anemia, decreased immunity and abnormal digestion (this anemia is known as megaloblastic anemia large, immature red blood cells) Folate and Vitamin B12 Folate & vitamin B12 depend on each other for activation during RBC synthesis & for homocysteine removal Folate can "mask" B12 deficiency by correcting anemia Elevated homocysteine levels have been associated with CVD & therefore, folate deficiency is associated with increased CVD risk Megaloblastic Anemia Folate Deficiency Folate deficiency is also associated with neural tube defects in newborns; a folate supplement is recommended for women of childbearing age (400 ug/day) Neural Tube Defects Neural tube develops in 1st month of gestation (before most women know they are pregnant) A defect in the formation of the neural tube (spinal cord, brain) during early fetal development Defect occurs when spinal column or skull don't form properly Spina Bifida is the failure of neural tubes to close Spinal cord bulges through the back Food Sources of Folate Liver Fortified breakfast cereals, pasta, rice and bread Beans Dark green leafy vegetables Orange juice Vitamin B12 Synthesized by bacteria and fungi Coenzyme Deficiency Role in folate metabolism Maintenance of the myelin sheaths RBC formation Pernicious anemia Nerve degeneration and paralysis Vitamin B12 and Folate vitamin B12 allows folate to be recycled Therefore, a deficiency of vitamin B12 may also lead to megaloblasitic anemia If the anemia caused by a vitamin B12 deficiency is "masked" by folate, and goes undetected, then nerve damage may ensue Amino Acid Metabolism B12 Absorption Requires a protein from salivary gland Requires stomach acid Requires intrinsic factor Absorbed in the last part of the small intestine About 50% of B12 is absorbed Intrinsic Factor A compound that is made by the stomach and is needed for vitamin B12 absorption Stomach acid liberates vitamin B12 from protein in food to which it is bound vitamin attaches to IF complex is absorbed into blood from small intestine A lack of intrinsic factor in some people, especially older adults, may necessitate monthly B12 injections directly into blood Anemia caused by a lack of IF is called pernicious anemia Therapy for Ineffective Absorption Many factors can disrupt this process Monthly injections of vitamin B12 vitamin B12 nasal gel Megadoses of vitamin B12 Allow for passive diffusion Food Sources of Vitamin B12 Synthesized by bacteria, fungi and algae Stored primarily in the liver of animals Animal products Organ meat Seafood Eggs Hot dogs Milk Vegans need to obtain sources from fortified products Vitamin C Also known as ascorbic acid Synthesized by most animals Decreased absorption with high intakes Excess excreted Sensitive to: Not by humans Cooking/heat Iron, copper, oxygen Functions of Vitamin C Synthesis of collagen Aids in iron absorption Supports immune function Antioxidant Aids the enzymes responsible for maintaining the tissue protein collagen, which is a part of all the connective tissues in the body (bones, teeth, skin, tendons); helps in wound healing & prevents bruising Protects iron from oxidation and recycles vitamin E Deficiency of Vitamin C Classic deficiency: Scurvy Deficient for 2040 days Fatigue, pinpoint hemorrhages Bleeding gums Weakness Fractures Associated with poverty Scurvy Food Sources of Vitamin C Citrus fruits Potatoes Green pepper Broccoli Strawberries Romaine lettuce Spinach Dietary Antioxidants A dietary antioxidant is a compound naturally found in foods, that decreases the negative effects of oxidation in the body They include vitamins C, E, A (betacarotene and other carotenoids), phytochemicals and selenium The body uses oxygen to produce energy; in this process, free radicals are sometimes formed (atoms or molecules that contain an unpaired electron), which make them highly reactive and unstable Free radicals can also be formed from environmental factors, such as radiation, pollution and tobacco smoke that act as oxidants (compounds that oxidize or remove an electron from other compounds) Dietary antioxidants are useful under conditions of oxidative stress, when free radicals in the body exceed its defenses against them Dietary Antioxidants Free radicals start a chain reaction of oxidative events the unstable molecule "steals" an electron from another molecule, which in turn takes an electron from another molecule, and so on The body has its own defenses against oxidation; these include antioxidant reserves and oxidationopposing enzyme systems Research has shown that antioxidants from foods are more effective than those taken in supplement form In this process, fatty acids in cell membranes are disrupted, damaging the cell's ability to transport substances Fatty acids in LDL are often oxidized as well DNA is another common "victim" of oxidative stress, and any cell that inherits this damaged DNA will be affected Oxidation is often the precursor to conditions such as CVD & cancer Antioxidants do not occur in isolation in foods, but occur in tandem with other vitamins, minerals and phytochemicals It is difficult to determine which component found in foods that are high in antioxidants (namely, fruits & vegetables) is responsible for the protective health benefits seen with high intakes Free Radicals Dietary Antioxidants Antioxidants may protect against these conditions: Certain cancers (lung, breast, cervical, esophageal, stomach and colon) Heart disease (stroke, HTN) Macular degeneration (agerelated) Aging (cataracts) Others Phytochemicals Natural compounds found in all plants (usually plant pigments) Not classified as nutrients Brightly or deeplycolored fruits & vegetables generally contain the most phytochemicals Many phytochemicals help to prevent/fight disease via their antioxidant properties How Do They Work? Phytochemicals: Some plant pigments are powerful antioxidants Act as hormoneinhibiting substances to prevent initiation of cancer Are antioxidants that prevent and repair damage due to oxidation Block enzymes that promote cancer and other diseases Modify absorption, production, or utilization of cholesterol Decrease formation of blood clots Zeaxanthin, anthocyanin and lycopene are strong antioxidants Dark chocolate contains flavonoid antioxidants Some phytochemical antioxidants reduce plaque formation by preventing the oxidation of LDL Phytochemicals Not essential; we do not develop a deficiency disease if we consume too little The body cannot make them; they must be obtained from the diet Phytochemicals are heat/light stable, and not easily destroyed by cooking or storage Many are excreted soon after ingestion, so intake of vegetables, legumes, nuts, fruits and other food sources should be maintained Cooking vegetables or eating with fat increases absorption of phytochemicals Characteristics Phytochemicals provide color, flavor and odor; protect plants from insects, microbes and oxidation due to exposure to sunlight and oxygen Some are components of a plant's energymaking processes, and others act as plant hormones Many are pigments; they function as antioxidants Citrus fruits and beans contain many phytochemicals Over 4000 identified We do not fully understand how they function or how much is needed by the body Some phytochemicals are "naturally occurring toxins" and can be harmful Sources & Functions 1. Carotenoids pigments responsible for red, dark green, yellow & orange colors in fruits & vegetables; act as antioxidants in the body carotene: found in broccoli, cantaloupe, carrots, pumpkin, spinach, squash, sweet potatoes Converted to vitamin A in the body Antioxidant prevents damage from free radicals Lutein: found in broccoli, Brussels sprouts, collard greens, kiwi, Romaine lettuce, spinach (green, leafy vegetables) Helps to prevent macular degeneration (vision) Lycopene: found in tomatoes, especially cooked tomato products, red peppers, pink grapefruit, watermelon Reduces risk for prostate cancer, heart disease and cancers of the GIT Sources & Functions (cont) 2. Resveratrol: found in red grapes, red grape juice, red wine Relaxation of smooth muscles, which decreases blood pressure May increase HDL cholesterol (good) Flavonoids act as antioxidants in the body Reduces risk for heart disease, cancer, blood clots, stroke 3. Prevent urinary tract infections Anthocyanins: found in blueberries, cherries, cranberries, plums, strawberries Organosulfur Compounds 4. Decrease blood cholesterol and blood pressure; reduce risk for certain cancers 5. Allium compounds found in garlic, onions, chives, leeks, scallions Sulphoraphane decreases risk for colon cancer Indoles decrease risk for breast cancer Sulphoraphane & Indoles found in cruciferous vegetables Other Phytochemicals Chocolate (especially dark) HDL cholesterol Capsaican (hot peppers, black pepper) Decrease blood clots Decrease risk of heart disease Phytosterols Act like hormones (estrogen) Thought to reduce the risk of several cancers Found in soy products and legumes Populations that consume a lot of soy have lower rates of breast and prostate cancer, osteoporosis, heart disease and women have less menopausal symptoms (hot flashes, bone loss) Types of Phytosterols Genistein (soybeans): inhibits breast, prostate, colon and ovarian cancers May reduce risk of osteoporosis Fresh is best Ways to Increase Phytochemical Intake Leave skin on when possible Exception tomatoes; canned fruits and vegetables also good source of phytochemicals Steam, broil, stir fry when you cook Avoid boiling Eat a variety of foods Ways to Increase Phytochemical Intake (cont) Strive for 5 servings of fruit and vegetables Eat a variety of brightly colored foods Use herbs and spices in cooking Extracts a...
View Full Document

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern