Chapter 13. Water soluble Vitamins 10/27/ substances

Size: px

Start display at page:

Download "Chapter 13. Water soluble Vitamins 10/27/ substances"

Robert Whitehead
6 years ago
Views:

1 Chapter 13 9 substances Most are cofactors for enzymes in energy producing pathways Amino acid metabolism, DNA synthesis, RBC synthesis Synthesis of other compounds Small amounts stored in the body Excreted through the kidneys Only 4 have a UL Cofactor any compound that participates with an enzyme to make it active Coenzyme a cofactor that is an organic compound Apoenzyme inactive, missing the cofactor Holoenzyme active, has the cofactor

Milled grains have bran and germ removed Endosperm mostly starch and a little protein,

legumes, whole grains, fortified cereals Cooking, especially alkaline conditions,

2 Milled grains have bran and germ removed Endosperm mostly starch and a little protein, 83% of kernel Since late 1940s, flour is enriched in thiamin, riboflavin, niacin, and folic acid. Thiamin B 1 In a variety of foods, though relatively low levels Pork, sunflower seeds, legumes, whole grains, fortified cereals Cooking, especially alkaline conditions, destroys it (bread decrease 20 30%) 1.2 mg/day for adult males 1.1 mg/day for adult females 1.5 mg/day Thiamin Average USA intake is above the RDA No UL from food or supplements

Thiamin Absorption by active transport Small amount is stored in muscle, brain, liver, and kidneys Transport as thiamin pyrophosphate (coenzyme form) Function TPP decarboxylation reaction Transition

3 Thiamin Absorption by active transport Small amount is stored in muscle, brain, liver, and kidneys Transport as thiamin pyrophosphate (coenzyme form) Function TPP decarboxylation reaction Transition reaction 2 steps in the citric acid cycle Especially important in nervous tissue Convert glucose to ribose for nucleic acids Thiamin Deficiency Beriberi Weakness, muscle pain, enlarged heart, poor memory, confusion, peripheral neuropathy Dry form nervous and muscular Wet form plus cardiovascular system, congestive heart failure leads to edema Initial signs within 14 days on thiamin free diet Alcoholics Poor absorption Increased excretion Poor diets Wernicke Korsakoff syndrome involves vision related problems and ataxia (8 10 times more common in alcoholics) Thiamin NIH Datasheets B 2 Milk is a common source plus enriched cereals Rapidly degraded by UV light HealthProfessional/

4 1.3 mg/day for adult males 1.1 mg/day for adult females 1,7 mg/day Average USA intake is above RDA Absorption HCl releases riboflavin from bound form Absorbed by active transport in small intestine Transport in blood on a carrier Converted to active coenzyme form in the tissues Boiling foods removes riboflavin No UL has been set, excess rapidly excreted through kidneys Functions Component of flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN) Electron transport from the citric acid cycle Metabolism of other B vitamins; niacin, pyridoxal phosphate, folate Antioxidant function Pharmacological Use Reducing migraine headaches Deficiency Ariboflavinosis Mouth, skin, RBC Inflammation of throat, mouth (stomatitis), tongue (glossitis) Seborrheic dermatitis Anemia, headaches, confusion Develops after 2 months on riboflavin free diet Individuals who rarely consume milk and meat products Alcoholics, poor absorption, some drugs, some diseases deficiency often with shortage of other B vitamins

tryptophan = 1 mg niacin 1 g of complete protein yields 10 mg tryptophan 90 g of protein yields 900 mg tryptophan 900 mg try x (1 mg niacin/60 mg try) = 15 mg

5 NIH Datasheet HealthProfessional/ 2 forms Nicotinic acid Nicotinamide Niacin B 3 Preformed niacin from food Synthesized from tryptophan Niacin Niacin 60 mg tryptophan = 1 mg niacin 1 g of complete protein yields 10 mg tryptophan 90 g of protein yields 900 mg tryptophan 900 mg try x (1 mg niacin/60 mg try) = 15 mg niacin Niacin intake = preformed niacin plus tryptophan intake 1 mg niacin = 1 niacin equivalent (NE) 60 mg try = 1 niacin equivalent 6 g complete protein = 1 niacin equivalent 16 mg/day for adult males 14 mg/day for adult females 20 mg/day UL 35 mg/day from supplements and fortified foods TOTAL CEREAL

Physiological Role: B-vitamins are coenzymes of many enzymes systems of body metabolism. Thiamine {B 1 }

Physiological Role: B-vitamins are coenzymes of many enzymes systems of body metabolism. Thiamine {B 1 } Food Constituents [continued] Micronutrients B-Vitamins The B group of vitamin {water soluble} includes: Thiamine: vitamin B 1, ant beriberi vitamin. Riboflavin: vitamin B 2. Niacin: nicotinic acid, PP