chapter_9_Water_Soluble_Vitamins-1-1
Page 1: Introduction
Title: Advanced Nutrition and Human Metabolism
Edition: Seventh Edition
Chapter 9: Water-Soluble Vitamins
Copyright Notice: © 2018 Cengage Learning. All rights reserved.
Page 2: General Characteristics of Vitamins (1 of 2)
Vitamins: Organic compounds with regulatory functions
Essential in the diet; necessary for health.
Classification:
Water-soluble vitamins
Fat-soluble vitamins
Storage: Water-soluble vitamins are not stored in the body.
DRIs (Dietary Reference Intakes) estimate needed intakes including:
RDAs (Recommended Dietary Allowances)
AIs (Adequate Intakes)
ULs (Tolerable Upper Intakes)
EARs (Estimated Average Requirements)
Page 3: General Characteristics of Vitamins (2 of 2)
Continuation of general characteristics (details not provided).
Page 4: Vitamin C (Ascorbic Acid)
Sources: Found in fruits and vegetables.
Digestion and Absorption:
No digestion required.
Absorption via SVCT1 and SVCT2 transporters.
Absorption decreases with high intake levels.
Transport: Primarily transported in blood in free form; higher concentrations in tissues than plasma.
Page 5: Vitamin C Functions (1 of 4)
Functions and Mechanisms of Action:
Antioxidant activity.
Acts as a cosubstrate for enzyme activity.
Essential in collagen synthesis, carnitine synthesis, tyrosine catabolism, and neurotransmitter synthesis (e.g., norepinephrine).
Page 6: Vitamin C Functions (2 of 4)
Continued functions:
Microsomal metabolism.
Pro-oxidant activity under certain conditions.
Other health benefits:
Cold prevention: enhances immune function.
Cancer: protective effects in various cancers (oral cavity, pharynx, esophagus, etc.).
Cardiovascular health and eye health.
Page 7: Vitamin C Nutrient Interactions and Excretion
Nutrient Interactions:
Enhances nonheme iron absorption.
Metabolism and Excretion:
Excreted or oxidized to dehydroascorbate; primarily oxidized in the liver with some in kidneys.
Page 8: Vitamin C Overview (4 of 4)
Summary of previous pages on Vitamin C (details not provided).
Page 9: Vitamin C: Recommended Dietary Allowance
Recommended Dietary Allowance (RDA):
Men: 90 mg/day
Women: 75 mg/day
Pregnancy: 100 mg/day
Lactation: 120 mg/day
Additional 35 mg/day recommended for smokers.
Page 10: Vitamin C Deficiency
Scurvy: Can develop in as little as 1 month due to deficiency.
Symptoms: 4 Hs of scurvy:
Hemorrhagic signs
Hyperkeratosis of hair follicles
Hypochondriasis (psychological manifestation)
Hematologic abnormalities
Treatment: 100–500 mg daily until cured.
Page 11: Vitamin C Toxicity
Tolerable Upper Intake Level (UL): 2 g/day.
Possible side effects of high doses:
Osmotic diarrhea
Increased risk of kidney stones
Caution for individuals predisposed to kidney stones or certain iron metabolism disorders.
Assessment of nutriture: plasma concentrations.
Page 12: Thiamin (Vitamin B1)
Sources: Widely distributed, found in pork, legumes, and enriched grains.
Stability: Easily destroyed by heat and alkalinity.
Digestion and Absorption: Present in free form in plants; TDP or TPP in animal foods and needs phosphorylation in intestines.
Page 13: Thiamin Absorption
Inhibition of absorption by antithiamin factors (e.g., thiaminases in raw fish).
Absorption occurs in jejunum via diffusion or carriers (ThTr1 and ThTr2).
Ethanol can interfere with absorption.
Transportation: Free, bound to albumin, or as thiamine monophosphate (TMP).
Page 14: Thiamin Functions
Functions:
Energy production and nutrient metabolism (as a coenzyme).
Role in synthesis of pentoses and NADPH.
Supports nervous system functions (non-coenzyme role).
Page 15: Thiamin Metabolism and Excretion
Metabolism: Excreted intact or catabolized.
RDA:
Men: 1.2 mg/day
Women: 1.1 mg/day
Pregnancy: 1.4 mg/day
Lactation: 1.5 mg/day
Deficiency: Results in beriberi (dry, wet, and acute types) and Wernicke’s encephalopathy.
Page 16: Thiamin (2 of 2)
Toxicity: No established Tolerable Upper Intake Level.
Assessment of nutriture: Evaluated by measuring erythrocyte transketolase activity in hemolyzed whole blood or thiamine in blood/urine.
Page 17: Riboflavin (Vitamin B2)
Sources: Found in milk, meat, eggs, and enriched grain products.
Stability: Destroyed by sunlight.
Digestion/Absorption: Riboflavin exists as FAD, FMN; absorbed by energy-dependent transporters in proximal small intestine.
Page 18: Riboflavin Absorption
Further absorption: Phosphorylated to FMN, then dephosphorylated back to riboflavin.
Transport: Converted and transported to liver for conversion back to FMN and FAD.
Concentrations highest in liver, kidney, and heart.
Page 19: Riboflavin Metabolism and Excretion
Excretion: Primarily in urine (turns urine bright orange-yellow).
RDA:
Men: 1.3 mg/day
Women: 1.1 mg/day
Pregnancy: 1.4 mg/day
Lactation: 1.6 mg/day
Page 20: Riboflavin Deficiency
Deficiency: Ariboflavinosis (symptoms: angular stomatitis, cheilosis, glossitis, hyperemia, edema).
Toxicity: None established Tolerable Upper Intake Level.
Assessment: Activity of erythrocyte glutathione reductase and urinary excretion rate.
Page 21: Riboflavin Functions (1 of 2)
Function: Acts in flavoproteins in the electron transport chain.
Involved in Vitamin B6 metabolism and choline catabolism.
Functions in oxidative decarboxylation of pyruvate, succinate dehydrogenase, and fatty acid beta-oxidation.
Page 22: Riboflavin Functions (2 of 2)
Additional Functions: Requires FAD for sphinganine oxidase action, essential for folate synthesis, synthesis of niacin from tryptophan, and involvement in various redox reactions.
Page 23: Niacin (Vitamin B3)
Sources: Found in fish, meats, and enriched grain products; supplements may offer nicotinamide.
Synthesis: Mangaged by the liver from tryptophan (1 mg Niacin from 60 mg dietary Tryptophan).
Page 24: Niacin Absorption
Absorbed in small intestine - NAD and NADP hydrolyzed to free nicotinamide.
Absorption via carrier-mediated diffusion.
Transported as nicotinamide and as nicotinic acid, trapped in cells as NAD/NADP.
Page 25: Niacin Functions
Functions include:
Coenzymes for oxidative reactions and reductive biosynthesis.
Non-redox roles including ADP-ribosylation reactions (e.g. various enzymes).
Page 26: Niacin Metabolism and Excretion (1 of 2)
Metabolism: NAD/NADP is degraded to nicotinamide and ADP-ribose.
Excretion: Organs excrete metabolites mainly through urine.
RDA:
Men: 16 mg NE/day
Women: 14 mg NE/day
Pregnancy: 18 mg NE/day
Lactation: 17 mg NE/day
Page 27: Niacin (2 of 2)
Deficiency: Pellagra characterized by 4 Ds: dermatitis, diarrhea, dementia, and death.
Toxicity: Large doses can treat hyperlipidemia, UL = 35 mg/day.
Assessment: Measuring urinary metabolites, serum/RBC indicators; NAD:NADP ratio.
Page 28: Pantothenic Acid (1 of 5)
Widely distributed in foods.
Digestion, absorption, and transport: Exists in free and bound forms (Coenzyme A) and absorbed in jejunum by passive diffusion.
Page 29: Pantothenic Acid (2 of 5)
Transportation: Transported in free form in blood.
Concentration: Highest in liver, adrenal gland, heart, kidneys, and brain.
Functions: Component of CoA and plays roles in nutrient metabolism, protein and drug acetylation, and fatty acid synthesis.
Page 30: Pantothenic Acid (3 of 5)
Excretion: Excreted intact in urine.
Adequate Intake:
Adults: 5 mg/day
Pregnancy: 6 mg/day
Lactation: 7 mg/day.
Page 31: Pantothenic Acid (4 of 5)
Deficiency: Burning foot syndrome, likely to occur with multiple nutrient deficiencies.
Toxicity: No reported toxicity.
Assessment: Blood concentrations and urinary pantothenic acid excretion.
Page 32: Pantothenic Acid (5 of 5)
Summary of previous pages on Pantothenic Acid (details not provided).
Page 33: Biotin
Sources: Found in liver, milk, soybeans, and egg yolk; avidin in raw egg whites binds biotin.
Production: Made by bacteria in the colon.
Digestion: Protein-bound biotin digested by enzymes (Biotinidase-Biocytin).
Page 34: Biotin Digestion, Absorption, Transport and Storage
Absorption: From bacteria in the proximal and mid-transverse colon is insufficient for body needs.
Transport: Absorbed by passive diffusion or carrier-mediated transport.
Storage: Small quantities in muscle, liver, and brain.
Page 35: Biotin Functions and Mechanisms of Action (1 of 2)
Coenzyme roles: Integral in various metabolic pathways.
Non-coenzyme roles include biotinylation, gene expression, and cell cycle regulation.
Page 36: Biotin Functions and Mechanisms of Action (2 of 2)
Enzymatic roles:
Pyruvate carboxylase: converts pyruvate to oxaloacetate.
Acetyl-CoA carboxylase: forms malonyl-CoA, crucial for fatty acid synthesis.
Key role in amino acid and fatty acid metabolism.
Page 37: Biotin Metabolism and Excretion (1 of 2)
Breakdown: Biotin holocarboxylases catabolized to biocytin, degraded to lysine and free biotin.
Excretion: Metabolites excreted in urine; non-absorbed biotin eliminated in feces.
Page 38: Biotin Metabolism and Excretion (2 of 2)
Adequate Intake:
Adults and Pregnancy: 30 µg/day
Lactation: 35 µg/day.
Deficiency: Rare but can result from consumption of raw egg whites.
Toxicity: No known toxicity or established UL.
Assessment: Blood and urinary excretion.
Page 39: Folate (1 of 4)
Difference: Folate (reduced form) vs. folic acid (oxidized form in fortified foods).
Page 40: Folate (2 of 4)
Sources: Concentrated in vegetables, higher in raw than cooked; destroyed by heat, oxidation, and UV light.
Fortification: Began in 1998, helping many Americans meet dietary recommendations.
Page 41: Folate (3 of 4)
Nutrient Interactions: Synergistic relationship with vitamin B12, association with various diseases.
Excretion: Eliminated in urine and feces.
RDA:
Adults: 400 µg DFE/day
Pregnancy: 600 µg DFE/day
Lactation: 500 µg DFE/day.
Page 42: Folate (4 of 4)
Deficiency: Can lead to megaloblastic macrocytic anemia.
UL: 1 mg for synthetic forms.
Assessment: Measured by plasma/RBC concentration, FIGLU excretion, and other tests.
Page 43: Folate Digestion, Absorption, Transport, and Storage
Polyglutamate forms hydrolyzed to monoglutamate, ready for absorption.
Transported in circulation as 5-methyl THF via specific transporter in enterocytes.
Page 44: Folate Functions and Mechanisms of Action (1 of 3)
Roles: Important in amino acid and choline metabolism, gene expression, and nucleotide synthesis.
Page 45: Folate Functions and Mechanisms of Action (2 of 3)
Functions: Outline of various folate forms and their metabolic roles, including purine and pyrimidine synthesis.
Page 46: Folate Functions and Mechanisms of Action (3 of 3)
Summary of folate's diverse roles in amino acid metabolism and methylation reactions.
Page 47: Dietary Folate Equivalents (DFE)
Definition: 1 DFE = 1 μg food folate, 0.6 μg folic acid from supplements with meals, 0.5 μg without meals.
Page 48: Vitamin B12 (Cobalamin)
Sources: Primarily from animal products, less in dairy; some plant-derived foods may be fortified.
Page 49: Vitamin B12 Digestion, Absorption, Transport, and Storage (1 of 4)
Process: Released from proteins in the stomach, binds to R proteins, then intrinsic factor in the duodenum.
Absorption: Occurs in ileum via specific receptors.
Page 50: Vitamin B12 Digestion, Absorption, Transport, and Storage (2 of 4)
Binding: In blood, cobalamin is bound primarily to TCII for transport; can be stored long-term in the body.
Page 51: Vitamin B12 Digestion, Absorption, Transport, and Storage (3 of 4)
Summary: Overall processes for absorption and transport of vitamin B12.
Page 52: Vitamin B12 Digestion, Absorption, Transport, and Storage (4 of 4)
Detailed explanation of B12 binding and absorption mechanisms in the gut.
Page 53: Vitamin B12 Functions and Mechanisms of Action (1 of 3)
Functions: Conversion of homocysteine to methionine and L-methylmalonyl CoA to succinyl CoA.
Page 54: Vitamin B12 Functions and Mechanisms of Action (2 of 3)
Recommended Dietary Allowance (RDA):
Adults: 2.4 µg/day
Pregnancy: 2.6 µg/day
Lactation: 2.8 µg/day.
Deficiency: Can lead to megaloblastic macrocytic anemia and neurological problems.
Page 55: Vitamin B12 Functions and Mechanisms of Action (3 of 3)
Toxicity: No known toxicity, no established upper intake level.
Assessment: Serum concentrations, methylmalonic acid levels, and Schilling test for absorption.
Page 56: Vitamin B12 Deficiency
Causes: Include altered gastric pH, destruction of parietal cells, pancreatic exocrine issues, and others.
Page 57: Vitamin B6 (1 of 4)
Sources: Found in plant foods, meats, fortified cereals; stable during cooking but can be lost in processing/storage.
Page 58: Vitamin B6 (2 of 4)
Metabolism: Major metabolite is 4-pyridoxic acid, excreted in urine.
RDA:
Adults age 19-50: 1.3 mg/day
Men 51+: 1.7 mg/day
Women 51+: 1.5 mg/day
Pregnancy: 1.9 mg/day
Lactation: 2.0 mg/day.
Page 59: Vitamin B6 (3 of 4)
Deficiency: Rare, but at-risk populations include older adults and heavy alcohol users.
Toxicity: In large doses can cause sensory and peripheral neuropathy; UL = 100 mg/day.
Page 60: Vitamin B6 (4 of 4)
Assessment: Nutritional status evaluated via plasma PLP concentrations, urinary vitamin B6, and other tests.
Page 61: Vitamin B6 Digestion, Absorption, Transport, and Storage
Process: Dephosphorylation to forms PN, PL, or PM; Absorbed primarily by passive diffusion.
Concentration: Most converted to PLP in liver and bound to albumin.
Page 62: Vitamin B6 Functions and Mechanisms of Action (1 of 2)
Key coenzyme functions:
Includes transamination, dehydration, decarboxylation, and more.
Page 63: Vitamin B6 Functions and Mechanisms of Action (2 of 2)
Non-coenzyme roles: Involved in gene expression modulation and other biochemical processes.
Page 64: Perspective 9: Genetics and Nutrition
Overview of genetics impacting folic acid needs and risk of chronic disease.
Page 65: Genetics and Nutrition (1 of 2)
Example: Folate's importance in nutrigenetics and its association with genetic variants among populations.
Page 66: Genetics and Nutrition (2 of 2)
Limitations in applicability of MTHFR testing for individuals; further research needed to clarify health impacts.