Vit D 3 pp - VITAMIN D Spring 2011 Vitamin D History:...

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VITAMIN D Spring 2011 Vitamin D History: Rickets Common in Childhood when Sunlight Exposure Limited-Industrial Revolution Vitamin D: History • Mellanby, 1918 – Fat soluble food facto factor – Rickets in dogs raised indoors cured with cod liver oil
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• Steenbock – irradiation process used to convert Vitamin D: History Steenbock precursors to active vitamin D in food • DeLuca: Steenbock’s student – active metabolites of vitamin D in humans – DeLuca still directing vitamin D research program and publishing Vitamin D: Nomenclature •Calciferol(vitamin D) –cholecalciferol (vitamin D 3 ) –ergocalciferol (vitamin D 2 ) –Synthesized by irradiation of D 2 precursor ergosterol in food
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Vitamin D2 and D3: Precursors and Differences in Structure Vitamin D: Food Sources • Natural vitamin D –Few concentrated sources •Fatty fish and fish liver oil •Chemical form –Cholecalciferol D3 Natural Food Sources of Vitamin D Dietary Sources of Vitamin D Natural Food Sources Serving Size Approximate IU Vitamin D Cod liver oil 1 tsp 400-1,000 Salmon, fresh wild caught 3.5 oz 600-1,000 Salmon, fresh farmed 3.5 oz 100-250 Salmon, canned 3.5 oz 300-600 Sardines, canned 3.5 oz 300 Mackerel, canned 3.5 oz 250 Tuna, canned 3.5 oz 236 Shiitake mushrooms, fresh 3.5 oz 100 Shiitake mushrooms, sun dried 3.5 oz 1,600 Egg yolk 1 yolk 20
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Farm-Raised Salmon Enclosures: Less Exposure to Sunlight Irradiation Of Mushrooms: Large Increases in Vitamin D 2 Wild-Salmon:NaturalSunlight Exposure • In US and Canada, milk is routinely fortified with vitamin D as are some orange juices, cereals, yogurts, cheeses, infant formula Vitamin D-Fortified Foods • In Europe only a few countries fortify with vitamin D Fortified Food Sources of Vitamin D Fortified Food Sources Serving Size Approximate IU Vitamin D Fortified milk 8 oz 100 Fortified orange juice 8 oz 100 Infant formulas 8 oz 100 Fortified yogurts 8 oz 100 Fortified butter 3.5 oz 56 Fortified margarine 3.5 oz 429 Fortified cheeses 3 oz 100 Fortified Breakfast cereals 1 serving 100
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Vitamin D: Synthesis • Skin – UV light (290-315 nm) – 7-dehydrocholesterol previtamin D 3 7 dehydrocholesterol – Previtamin D 3 Vitamin D 3 Ring opens @ C9-C10 Bloodstream Once previtamin D3 is synthesized in skin it can undergo either a photo conversion to lumisterol, tachysterol, and 7-DHC or a heat-induced isomerization to vitamin D3 cholecalciferol Vitamin D: Factors Affecting Synthesis • Natural exposure to sun • Latitude: northern less synthesis • Latitudes higher than 50 0 no cutaneous production on vit D±-periods of year – Finland (Helsinki) – Canada (Edmonton) – Alaska (Fairbanks) • Clouds, thick ozone can reduce vitamin D synthesis
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Vitamin D: Factors Affecting Synthesis •Season of year – Season: spring, summer more synthesis- vitamin D deficiency more common end of winter • Time of day-more uv irradiation middle of day • Clothing • Sunscreen-can prevent 100% uv exposure Vitamin D: Synthesis Pigmentation: melanin absorbs UV •Dark skinned individuals may require 5-10 X more sun exposure to generate
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Vit D 3 pp - VITAMIN D Spring 2011 Vitamin D History:...

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