1pp Thiamin Spring 2011

1pp Thiamin Spring 2011 - Thiamin Thiamin Spring 2011 2011...

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hiamin Thiamin Spring 2011
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Thiamin: History • Japanese naval surgeon first observed association of diet and beriberi –officers who consumed protein-rich diets healthy compared to lower ranked men with beriberi who consumed rice – Changed diet of lower ranked men to include more protein, switched rice to wheat flour or barley • Beriberi no longer a problem
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Thiamin: History • Dr. Eijkman Dutch medical researcher orking in Indonesia during late 1800’s working in Indonesia during late 1800 s • Fed chickens the same white rice consumed by humans who developed beriberi – rapid development of a polyneuritis • Chickens fed “brown rice” healthy
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Thiamin: History • Grijns, Funk, and Williams worked to purify compound in rice “polishings” that was curative factor for beriberi unk first used term “ itamine” • Funk first used term vitamine • Thiamin referred to as vitamine B1 • 1930s chemical structure identified
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Thiamin: Chemical Structure Essential features are linked pyrimidine and thiazole rings, hydroxyethyl side chain position 5 iazole ng which becomes hosphorylated the of thiazole ring which becomes phosphorylated in the cell and unsubstituted carbon at position 2 of thiazole ring
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Thiamin: Food Sources Pork muscle (0.78 mg/100 g) eef muscle (0 13 mg/100 g) Beef muscle (0.13 mg/100 g) Baker’s Yeast (2.33 mg/100 g) Peanuts Uncooked (1.14 mg/100 g Peanuts Cooked (0.18 mg/100 g) Fortified cornflakes (1.2 mg/100g) nriched rice (0.41 mg/100 g) Enriched rice (0.41 mg/100 g)
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Form of Thiamin in Food ajority of thiamin in food in Majority of thiamin in food in phosphorylated form except fortified foods andatory fortification of Mandatory fortification of “enriched” cereal grain products in US
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Stability of Thiamin in Food lkaline pH such as use of bicarbonate •Alkaline pH such as use of bicarbonate during cooking to preserve the green lor increases thiamin destruction color increases thiamin destruction •Unstable to heat and oxygen •Cooking in large volumes of liquid – leaches into liquid –often discarded •Use of sulfite to preserve food can result in major chemical breakdown –splits methylene bridge
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Antithiamine Compounds in Food •Thiaminases are thiamine-splitting enzymes in raw fish and ferns –Can destroy thiamine during food storage, during its preparation, and in the G.I. tract –Inactivated by cooking •Polyphenolic compounds such as nnic acid olorogenic cid and tannic acid, cholorogenic acid, and caffeic acid in –Coffee, tea, betel nuts, ferns –Heat stable
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Antithiamin Factors Cleave Thiamin Molecule
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Thiamin: Absorption • Thiamin phosphate in food converted to pp free thiamin by phosphatases oth free thiamin and thiamin • Both free thiamin and thiamin monophosphate can be actively absorbed • Low intake: saturable active transport ompetitively inhibited by thiamin analogs Co pet t e y b ted by t a a a ogs • Large dose: passive diffusion
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1pp Thiamin Spring 2011 - Thiamin Thiamin Spring 2011 2011...

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