HUEC 3115 Human Nutrition and Metabolism Water Soluble Vitamin Charts Functional Form Vitamin C Ascorbic Acid L isomer is the active form Humans are one of few mammals that cannot synthesize vitamin C because we lack gulonolactone oxidase Absorption Occurs throughout the small intestines including the ileum assisted via SVCT1 high capacity SVCT2 low capacity Both are sodium transporters Absorption decreases with higher intakes Maximal absorption 2g Dehydroascorbate oxidized form of vitamin C absorbed via GLUT1 and GLUT3 and converted to ascorbic acid form Transported in the blood in the free form Ascorbic acid uptake into body cells via SVCT1 and SVCT2 SVCT2 not present in skeletal muscle and lungs Transportati on Food Sources Fruits and vegetables citrus products Supplements free ascorbic acid Usual intake 30 180mg day and absorbed at 70 90 Functions Tyrosine synthesis and catabolism Neurotransmitter synthesis Serotonin and Norepinephrine Collagen synthesis Carnitine synthesis Microsomal metabolism Antioxidant activity by acting as a reducing agent Pro oxidant activity only at non physiological conditions Cancer Cardiovascular Disease Eye Health benefits against cataracts Enhances the absorption of nonheme iron Men 90mg Women 75mg Pregnancy 100mg Lactation 120mg Increased RDA for smokers Based on maximizing tissue concentration and minimizing urinary excretion Scurvy body pools below 300mg and plasma vitamin C below 0 2mg dL UL 2g Excreted intact or oxidized to dehydroascorbic acid Isolated in 1928 by Szent Gyorgyi and King Structure in 1 Role in Disease Prevention Interactions with other Nutrients RDA Deficiency Toxicity Excretion History HUEC 3115 Human Nutrition and Metabolism Water Soluble Vitamin Charts 1932 by Haworth Vitamin B1 Thiamin Functional Form Consists of a pyrimidine ring attached to a thiazole by a methylene bridge Found in plants in nonphosphorylated form free form Found in animals as thiamin diphosphate TDP aka thiamine pyrophosphate TPP Absorption Occurs in the jejunum as free thiamin Absorption is both Functions Energy transformation oxidative decarboxylation of Transportati on Food Sources RDA Deficiency Toxicity Excretion History active and passive Involves two carriers ThTr1 and ThTr2 Crosses the basolateral membrane into blood via hydrogen antiport Transported free bound to albumin or as TMP Enters red blood cells via facilitated diffusion but entering other cells requires energy After absorption into portal blood it is taken up by the liver and converted to TDP inside of cells Widely available in foods especially enriched grains Sensitive to heat oxygen and low acid conditions pyruvate Synthesis of pentoses and NADPH Nerve conduction noncoenzyme role 1 2mg Men 1 1 mg Women 1 4 mg Pregnancy 1 5 mg Lactation Beriberi impairment of the nerves and heart Associated with alcoholism decreased food consumption liver damaged decreases TDP formation and decreased absorption No UL High does used in treatment of maple syrup urine Excreted intact or catabolized Isolated in 1912 by Funk Structure by Williams in 1930 Discovered by chicken fed a diet of polished rice Vitamin B2 Riboflavin Functional Form FAD Flavin adenine dinucleotide is the coenzyme form FMN Flavin mononucleotide Riboflavin free form 2 HUEC 3115 Human Nutrition and Metabolism Water Soluble Vitamin Charts Absorption HCL in the stomach and enzymatic hydroloysis frees Functions Oxidation reduction reactions riboflavin FAD FMN Riboflavin Absorption is by riboflavin transporter 2 RFT2 in the proximal small intestines Sodium independent Absorbed riboflavin is converted to FMN in the intestinal cells then back to riboflavin to transport Alcohol impairs absorption Transported mainly by albumin Enters cells by riboflavin binding proteins The liver kidney and heart has the greatest amount FAD predominates in tissues Animal origin foods are usually good sources Milk and milk products contribute the most In most foods riboflavin is in the free FMN or FAD state Electron transport chain Oxidative decarboxylation of pyruvate Oxidative decarboxylation of alpha ketoglutarate Fatty acyl CoA dehydrogenase Synthesis of 5 methyl tetrahydrofolate THF Pyridoxine phosphate oxidase converts PMP to PNP to PLP the coenzyme form of vitamin B6 Transportati on Food Sources Interactions with other Nutrients RDA 1 3mg for Men 1 1mg for Women 400mg is used to treat migraines Deficiency 1 4 serum level Toxicity Excretion History Ariboflavinosis No UL Excreted in the urine intact Discovered in 1917 by Paul Gyorgy Following egg white injury in rats Vitamin B3 Niacin Functional Form Nicotinic acid Nicotinamide found in supplements NAD and NADP coenzyme forms Absorption NAD and NADP converted to nicotinamide for absorption Transportati on Pyrophosphate removes phosphate off of NADP Absorbed by sodium dependent carriers by facilitated diffusion Movement into cells by simple diffusion but carriers required for entrance into red blood cells Nicotinamide converted to coenzyme forms NAD and NADP 3 HUEC 3115 Human Nutrition and Metabolism Water Soluble Vitamin Charts Food Sources Bodily Sources Interaction with other Nutrients Functions Coenzyme forms used in glycolysis oxidative Fish and other animal flesh In animals found in coenzyme forms of NAD and NADP Production of NAD from tryptophan in the liver 60mg of tryptophan required to produce 1mg NAD Riboflavin FAD vitamin B6 PLP and iron involved in conversion of tryptophan to NAD RDA Deficiency Toxicity Excretion History Functional Form decarboxylation of pyruvate to acetyl CoA oxidation of acetyl CoA in TCA cycle beta oxidation of fatty acids Transfer of elections and hydrogen from metabolic intermediates in electron transport chain Can be reduced into NADPH Nonredox roles Recommendation given in niacin equivalents Accounts for the 1mg of niacin that can be produced from 60mg of tryptophan 16mg for Men 14mg for Women Pellagra Dermatisis dementia diarrhea and death UL based on flushing is 35mg day from supplements and fortified foods Large does 6g day are used to treat hypercholesterolemia Converted in the liver to a variety of excretion products NAD and NADP can be recycled Used to assess niacin status Isolated in 1867 Goldberg did major research Vitamin B6 PN Pyridixine PL Pyridoxal PM Pyridoxamine PNP Pyridoxine phosphate PLP Pyridoxal phosphate Coenzyme form PMP Pyridoxamine phosphate Absorption Absorbed in the dephosphorylated form at normal dietary levels Absorbed in the jejunum by