Vitamin K.pdf

HNUT10010 HNUT10020 Human Nutrition 1: Understanding Nutrients Aifric O’Sullivan BSc, MSc, PhD UCD Institute of Food and Health School of Agriculture and Food Science Vitamin K Limited stores at birth and insufficient intake from breast milk Vitamin K deficiency-related bleeding (VKDB) presents w...

HNUT10010 HNUT10020 Human Nutrition 1: Understanding Nutrients Aifric O’Sullivan BSc, MSc, PhD UCD Institute of Food and Health School of Agriculture and Food Science Vitamin K Limited stores at birth and insufficient intake from breast milk Vitamin K deficiency-related bleeding (VKDB) presents within 24 hours of birth HSE 2004 “All babies should receive one dose of vitamin K prophylaxis at birth.” Vitamin K vitamin K activity 2-methyl 1,4-naphthoquinone ring Phylloquinone Green leafy vegetables Menaquinone Gut microbiota Menadiol Synthetic form The Nutrition Society Textbook Series, Introduction to Human Nutrition, Second Edition © 2009, 2002 Vitamin K Sources Food Serving Olive oil 1 Tablespoon 8.1 Broccoli, cooked 1 cup (chopped) 220 Kale, raw 1 cup (chopped) 547 Spinach, raw Leaf lettuce (green), raw Parsley, raw 1 cup 145 1 cup (shredded) 62.5 1/4 cup 246 + Intestinal bacteria Vitamin K (ug) μg Vitamin K Requirements Vitamin K Status • “Prothrombin time” – Ca + thromboplastin • Plasma preprothrombin (little or no Gla) Adequate Intake • Difficult to determine • 1 µg/kg body weight • 65-80 µg day Vitamin K Sources, Synthesis and Metabolism • Phylloquinone – Green leafy vegetables – spinach, Brussels sprouts – Absorbed in small intestine in micelles (80%) • Menaquinone – Synthesized by intestinal bacteria – Absorbed by passive diffusion from ileum and colon • Both forms are released from the liver in VLDLs Vitamin K: Blood Clotting Vitamin K Metabolic Function Vitamin K dependent enzyme 1. Carboxylation of glutamate GLA Vitamin K is a cofactor in the carboxylation of glutamate residues which activates specific proteins GLA can bind calcium which is required for blood clotting and bone formation The Nutrition Society Textbook Series, Introduction to Human Nutrition, Second Edition © 2009, 2002 Vitamin K Metabolic Function Vitamin K dependent enzyme 1. Carboxylation of glutamate Activated protein Inactive protein Glutamic acid residue K dependent enzyme Active Vitamin K Gla Bind Calcium Inactive Vitamin K clotting proteins to membrane The Nutrition Society Textbook Series, Introduction to Human Nutrition, Second Edition © 2009, 2002 Vitamin K Metabolic Function • Blood clotting Activated protein – Activates clotting factors Gla – Prothrombin to thrombin – Fibrinogen to fibrin, forms clot Bind Calcium • Bone formation – Osteocalcin and bone matrix Gla – Skeletal proteins to bind calcium – Effects bone mineralisation Vitamin K Deficiency/Toxicity • Deficiency is rare in adults but some newborn infants have low reserves – – – – Sterile intestinal tract, low levels in breast milk Some develop Vitamin K Deficiency Bleeding VKDB Can result in uncontrolled internal bleeding Single dose of vitamin K given at birth • No evidence of toxicity – No dietary upper limit – High doses can reduce effectiveness of anticoagulant drugs (e.g. Warfarin) Reading • Gibney M, Lanham-New S, Cassidy A, Vorster H, eds. Introduction to Human Nutrition. 2nd ed: Wiley-Blackwell, 2009. Chapter 8 • Gropper SS, Smith JL. Advanced Nutrition and Human Metabolism, International Edition 6th ed: Wadsworth Cenage Learning, 2013. Chapter 9/10 • Whitney E, Rolfes SR. Understanding Nutrition, 13th Edition: Wadsworth, Cengage Learning, 2013. Chapter 10/11