NUTR 1000 – 003Exam # 3 Study Guide Lectures: 11 - 18Lecture 11 (October 13)Chapter 7: Vitamins• Vitamins are either fat-soluble or water-soluble– Fat-soluble vitamins (A, D, E, and K) are absorbed with dietary fat and can be stored in body • Are absorbed into the lymph and require dietary fat for absorption • Once in the blood, they are transported by protein carriers; can be stored in the liver or with other lipids in fatty tissues – Water-soluble vitamins (B vitamins and C) are absorbed with water and enter thebloodstream directly• Not stored in body, but excesses can still be harmful• Absorbed directly into the bloodstream, where they travel freely• Excesses are excreted in the urineSolubility gives to the vitamins many of their characteristics: It determines how they are absorbed into and transported around by the bloodstreamWhether they can be stored in the body andHow easily they are lost from the body.- Some vitamins function as antioxidants, substances that neutralize free radicals.o Vitamins A, C, and E and beta-carotene are antioxidantso Free radicals are unstable oxygen-containing molecules that can damage the cells of the body and possible contribute to increased risk of chronic diseasesNot all vitamins in food are usable by the body.- Bioavailability is the degree to which a nutrient is absorbed from foods and used in the body.o Amount of vitamin in the foodo Food is cooked, raw or refinedo Digestion and absorptiono Nutritional statuso Natural or synthetic o Ex. The more you need, the more is absorbedProvitamins- Not a vitamin but can be converted once absorbed- beta-carotene=Vitamin AThe Fat-Soluble Vitamins- A, D, E, and Ko Food sources-found in fats and oils of foodso Requires bile for absorption- Storageo In the liver and fatty tissues until neededo Toxicity can occur- Deficiency-due to low intake and/or mal-absorptive diseases o HIV/Aidso Celiac Dzo Liver DzVitamin A : retinoids (retinol, retinal, retinoic acid)- Retinol most usable- Preformed vitamin A o only found in animal foods: liver, eggs, fortified milk and cheese- Provitamin A carotenoids, which are converted to retinol in your bodyo Carotenoids---pigments that give color to carrots, cantaloupe, sweet potatoes, spinach, broccolio 600 different ones as phytochemicalso Beta-carotene only to Vit A- Functionso The most familiar function of vitamin A is to sustain normal eyesight. o Vitamin A plays two roles in this: The process of light perception at the retina  The maintenance of the cornea (crystal clear outer window)o (1) Light perception When light falls on the eye, it passes through the clear cornea and strikes the cells of the retina. Retina has 2 types of cells, rods and cones Cones allow us to see coloro Rods distinguish black from white Rods contain rhodopsin molecules (which has Vit A) Light bleaches out the rhodopsin which causes the vitamin A portion to break off This sends a message to the brain This signal is interpreted by the brain as a recognizable imageo Vitamin A reunites with the pigment, but a little bit of the vitamin A is destroyed each time this reaction takes place. o New vitamin A is needed to replenish the supply.o Other roles of Vitamin A ANTI-OXIDANT properties Cell differentiation- Non-specialized, immature cells become specialized and mature Growth and Reproduction Immunological functions- Protective barrierso skin—lungs, gi, kidneyso antibodies Bone health- Necessary for the dismantling of existing bone tissue and rebuilding for new growtho Stunted growth--first sign of Vitamin A def. - Daily Needs: o Adult males: 900 micrograms retinol activity equivalents (RAEo Adult females: 700 microgramsVitamin Eo 8 naturally occurring forms with Alpha-tocopherol as the most active form in bodyo Functions:o 1---Acts as a powerful antioxidant Protects cell membranes prevents oxidation of LDL cholesterol Reduces atherosclerosis o 2---Acts as an anticoagulant inhibiting formation of harmful clots inside bloodstreamo Daily needs: Adults need 15 mg of alpha-tocopherol equivalents Americans getting only 9 mgVitamin Ko Two forms of vitamin Ko Menaquinone synthesized by intestinal bacteriao Phylloquinone found in green plantso Functions:o Essential for blood clotting Involved in synthesizing four blood clotting factorso Important to bone healtho Enables bone protein osteocalcin to bind with calciumo Daily Needs: o Men need 120 micrograms/dayo Women need 90 micrograms/dayVitamin Do Called "sunshine vitamin" because it is made in the body with help of sunlight (UV)o Cholesterol-containing compound in skin is converted to inactive form of vitamin Do People with insufficient sunlight exposure must meet needs through dieto Two forms of vitamin D in foodo Ergocalciferol (vitamin D2) Plant-based foods ---especially mushroomso Cholecalciferol (vitamin D3) Animal-based foods (especially cod liver oil) Synthesized in the bodyo All vitamin D undergoes chemical transformations in the liver and kidneys to activate it.o Functions: active form acts as a hormoneo Regulates two important bone minerals: calcium (Ca) and phosphorus (P) Stimulates intestinal absorption of Ca and P to maintain healthy blood levels andbuild and maintain bones  When dietary calcium is inadequate, vitamin D and parathyroid hormone cause calcium to leave bones to maintain necessary blood levelso May aid prevention of some cancers, diabetes, heart disease, and other conditionso Daily Needso Today’s world---Sun exposure cannot meet everyone's vitamin D needs Skin pigment melanin and use of sunscreen reduce vitamin D production Sunlight intensity during winter in northern and southern latitudes not sufficientto make vitamin D o Therefore, vitamin D needs are based on dietary sources o Adults: 15 to 20 µg (600 to 800 IU) per day, depending on ageo Food sources: fortified milk and yogurt, fortified cereals, fatty fish (examples: sardines, salmon) Overuse of supplements may lead to hypervitaminosis D, which causes hypercalcemia- Damaging calcium deposited in kidneys, lungs, blood vessels, heart- UL: 4,000 IU (100 µg) Too Little Vitamin D presents a danger to the bones- Rickets: vitamin D deficiency disease in childrenLecture 12 (October 15)(Chapter 7 cont’d…)The B Vitamins and Vitamin C are Water-Solubleo Water soluble vitamins are not stored in the body; excess is excreted in urineo B vitamins share common role as