4 Phosphorus.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 Phosphorus • Skeleton (85%) • Soft tissues (15%) • Mostly found in combination with oxygen as phosphate Phosphate ion Phosphorus...

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 Phosphorus • Skeleton (85%) • Soft tissues (15%) • Mostly found in combination with oxygen as phosphate Phosphate ion Phosphorus Foods Food (mg) Milk 200 ml 247 Yogurt 1 tub 385 Cheese 28g 131 Egg 1 large 104 Beef 100g 173 Chicken 100g 155 Turkey 100g 173 Salmon 100g 252 Bread, whole grain 1 slice 57 Bread, white 25 1 slice * Serving size 100 g = deck of cards Another micronutrient that is widely distributed Phosphorus RDA mg/d 1-10 years 300-450 11-17 years 625-775 18+ years Pregnancy 550 950 Phosphorus Absorption and Metabolism Regulation is similar to calcium Urine = dietary intake 55-70% 1 2 Passive Concentration dependent Active Vitamin D dependent Filtration Blood 13 mmol/L = 12 mmol/L phopholipids 1 mmol/L inorganic phosphate Resorption RBCs, plasma lipoproteins * 1. 2. 3. 4. Absorption from food Resorption from bone Urinary phosphorus Cell and tissue source Phosphorus Metabolic Function • Structure – Phosphorus occurs as hydroxyapatite in bone and – Phospholipids, which are a major component of most biological membranes, important for lipid transport – Part of DNA • Other – Maintain PH: buffering of acid or alkali excesses – Energy storage: ATP (3 phosphate groups) – Phosphorylation: activation of enzymes Phosphorus Deficiency and Toxicity • Deficiency (rare) – Hypophosphatemia < 0.3 mmol/L – Only limited stores in cells rely on ECF* inorganic supply – Anorexia, anaemia, muscle weakness, bone pain, rickets, osteomalacia, increased infection, paraesthesia, ataxia, confusion and even death. • Toxicity – Hyperphosphatemia – Effects hormonal control of calcium – Calcification of tissues, particularly kidney *ECF, extracellular fluid Reading • Gibney M, Lanham-New S, Cassidy A, Vorster H, eds. Introduction to Human Nutrition. 2nd ed: Wiley-Blackwell, 2009. Chapter 9 • Gropper SS, Smith JL. Advanced Nutrition and Human Metabolism, International Edition 6th ed: Wadsworth Cenage Learning, 2013. Chapter 11-13 • Whitney E, Rolfes SR. Understanding Nutrition, 13th Edition: Wadsworth, Cengage Learning, 2013. Chapter 12-13