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December 2, 4 - Vitamins - Lecture Notes - LIFESCI 2N03

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McMaster University
Life Sciences
Danny M.Pincivero

LECTURE 8 LIFESCI 2N03 Vitamins December 2, 2013 History of Vitamins  James Lind – British physician, 1716, 1794 o Discovered needs of vitamin C in British sailors o Found feeding lime (citrus) to sailors was beneficial o Vitamin C necessary for collagen synthesis o Scurvy – disease caused by vitamin C deficiency  Signs and symptoms – fatigue, anemia (low RBC count), hemorrhaging, teeth loosening, softening of bones (bending, not brittle)  Casimir Funk – Polish biochemist; Feb 23, 1884-Nov 20, 1967 o Isolated an amine in rice – nitrogen containing functional group o Discovered – providing an amine improved the healthy of thiamin deprived chickens  Thiamin deprived – didn’t have any B1 o Referred to this “amine” as “vital” for life; therefore, we now have “vital” “amines” or vitamins Vitamins  Vitamins o Organic molecules o Required in small units (micrograms); quantified in µg or mg o Individual units – not chains like the macronutrients o Do not contribute to the body’s energy needs (in terms of kcal)  Allows cells to utilize fat, carbs and protein, but does not provide direct energy o Classification – fat soluble (A,D,E,K) and water soluble (B,C) o B vitamins tend to be involved in metabolic pathways  Absorption o Water soluble  Vitamin C  8 B-vitamins – B1 (thiamin), B2 (riboflavin), B3 (niacin), pantothenic acid, biotin, folate, B6, B12  Absorbed directly through intestinal cells and into CV system  Dissolved in blood so freely transported  Susceptible to kidney filtration – beyond storage capacity; not a large amount of storage  Not bound to anything (unlike fat soluble), small enough to get out of CV system and to be filtered by kidney  Taken in large dosages beyond what is needed by body, will be excreted as urine after filtration by kidney  Vitamin B12 is stored more than other water soluble vitamins  General rule  Need daily ingestion of water-soluble vitamins (not stored)  Eg/ Vitamin C deficiency symptoms manifest after 20-40 days  Toxicity – rare, but possibl6 (B most concern); ingest at levels above U.L. o Fat soluble  Absorbed with dietary lipids; packaged into the chylomicrons  Bioavailability = 40-90% of vitamins consumed  Efficiency decreases with greater caloric ingestion  Need lipids to absorb vitamins  Pathway  Lacteal – lymphatic system, CV system  Lipoproteins “broken up”  Chylomicron remnants taken up by liver (and broken up); stores vitamins o Eg/ beef liver – large amount of vitamins; also cholesterol  Vitamin B1 – Thiamin o Part of the co-enzyme TPP (thiamin pyrophosphate) – TPP works with PDH (pyruvate dehydrogenase; enzyme between pyruvate and Acetyl-coA; if pyruvate binds to PDH, it undergoes a one way reaction to become Acetyl-coA)  When PDH is active, 38 ATP are produced; no PDH, only 4 ATP made (glycolysis)  If PDH absent – LDH + pyruvate  lactic acid o RDA – 1.1 mg/day (women), 1.2 mg/day (men) o Deficiency  Caused by a reduction in food intake 1 LECTURE 8 LIFESCI 2N03  Beriberi – chronic thiamin deficiency, chronic weakness, weight loss  Brown vs. white rice – polish brown rice to remove bran layer making white rice; bran layer1has B  Fed chicken white rice to make chickens thiamin deficient  White rice –easier to cook, cook faster  Brown rice – healthier o Food sources – whole grains, pork  Vitamin B2 – Riboflavin o Co-enzyme (FMA, FAD) – picks up electrons and proteins, contributes to electron transport chain o Electron acceptor/transporter  Keeps energy pathway going o RDA – 1.1 mg/day (women), 1.3 mg/day (men) o Deficiency  Ariboflavinosis, inflammation of membranes (mouth, eyes, gastrointestinal system, skin)  Accompanies other micronutrient deficiencies o Food sources – milk and alternatives, whole grains, cereal products (fortified), white mushrooms  Vitamin B3 – Niacin o Nicotinic acid and nicotinamide; precursor for NAD and NADP o Can by synthesized from tryptophan (EAA) o Anti-oxidant, lipid cholesterol synthase (niacin has a role in lipid synthesis) o RDA – 14 mg NE/day (women), 16 mg NE/day (men)  NE = niacin equivalent o UL – 35 mg/day o Deficiency  Pellagra – 4 D’s; diarrhea, dermatitis, dementia, death o Food sources – animal products (eggs, milk, meat, poultry, fish), whole grains o Toxicity  Niacin flush – supplement form (3-4x RDA), nicotinic acid form  Blood vessel dilation, painful tingling sensation o Pharmacological doses – high doses to treat LDL cholesterol (must be monitored for side effects)  Biotin o Coenzyme, involved in the Krebs’s cycle o Part of pyruvate carboxylase (makes oxaloacetate from pyruvate) o Contributes to gluconeogenesis, fatty acid synthesis o AL = 30 micrograms/day o Deficiency  Caused by chronic consumption of raw egg whites  Egg whites contain avidin, which binds biotin  Skin rash, hair loss, neurological symptoms o Food Sources – egg yolks, soybeans, fish, whole grains  Pantothenic Acid o Part of co-enzyme A; makes Acetyl CoA o Synthesis of lipids, neurotransmitters, hormones, hemoglobin o Al = 5 mg/day o Deficiency – fatigue, neurological symptoms o Food sources – beef, poultry, whole grains, potatoes, tomatoes, broccoli  Vitamin B6 o Functions as a coenzyme 1. Protein Metabolism  11 non-essential amino acids  Without B6– all amino acids become essential  B6part of enzyme (amino transferase) to make non-essential amino acids 2. Blood Cell Synthesis  Red and white blood cells  Assists with oxygen binding to hemoglobin  Deficiency – microcytic hypochromic anemia o Red blood cell is smaller than normal and lacks Hb 3. Reduce Risk of Myocardial Infarction  High levels of homocysteine related to M.I. (plaque formation) o Homocysteine is a by product of cysteine; over excess is implicated in CVD  PLP-dependent enzymes convert homocysteine to cysteine o PLP = B 6 2 LECTURE 8 LIFESCI 2N03  Homocystinuria – inherited disease, lack of enzyme metabolizing cysteine o RDA  1.3 mg/day (men and women)  Men (>51 years) =1.7 mg/day  Women (>51 years) = 1.5 mg/day  U.L. = 100 mg/day o Sources – quite abundant in food sources  Fortified ready to eat cereals  Meat, fish, poultry  Bananas, watermelon, potatoes o Deficiency – rare; anemia, nervous system symptoms  Deficiency symptoms accompany other nutritional deficiencies o Toxicity  1000-2000 mg; leads to protein modification  Neurons affected; can lead to permanent nerve damage  Folate o 3 parts – glutamate, PABA, and pteridine o 3-11 glutamate molecules; only amino acid metabolized by brain neurons o Small Intestine – 1 glutamate remains; become folic acid (most stable form used in supplements and fortification) o Functions of folate – amino acid metabolism, DNA synthesis, cell division  Most critical in embryo formation – need folic acid o Recommendations  Empty stomach – 100% absorption in supplement form; decreases with food uptake  Natural folate in food = 50-67% bioavailability o RDA – 400 micrograms DFE/day, DFE = dietary folate equivalents o Pregnancy – 600 µg DFE/day o Lactation – 500 µg DFE/day  Supplements recommended during childbearing age o Requirements are elevated above basic 400µg DEF/day during pregnancy and lactation o U.L. = 1000 µg/day, toxicity linked 12deficiency (hives, altered RBC and neurological symptoms) o Folate Sources  Dark green leafy vegetables, asparagus, broccoli, legumes  Fortified foods – cereal grains, bread, pasta, rice  Romaine lettuce (1.5 cups = 115 micrograms) – higher concentration than iceberg lettuce  Iceberg Lettuce – little nutrients; contains fiber and water o Purpose of fortifying foods  Folate deficiency linked to birth defects (conception and early development) – women of child birthing age recommended to take supplements  Cooking easily destroys food sources of folate (steaming, stir-frying, microwaving) o Folate Deficiency – most prevalent deficiency; foods are fortified because folate is not as abundant in foods  Heart disease – elevated homocysteine levels  Megaloblastic anemia – due to impaired DNA synthesis in developing RBC  DNA synthesis impaired – RBC, WBC, and GI cells  Folate important in embryonic growth, fetal growth, newborn growth for DNA synthesis  Neural tube defects  Incomplete closure of spinal canal (spina bifida)  Anencephaly – part or all of brain missing o Body can store folate for 1-4 months  B12(cobalamin, cobalt-containing compounds) o Key role in folate metabolism o B12deficiency; can lead to folate deficien
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