Vitamin D.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 D “Vitamin D contributes to normal development of bones and teeth” EFSA 2014 Health claim application on vitamin D and n...

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 D “Vitamin D contributes to normal development of bones and teeth” EFSA 2014 Health claim application on vitamin D and normal development of bones and teeth pursuant to Article 14 of Regulation (EC) No 1924/2006 (Claim serial No: 0098_FR). February 2008. Submitted by Specialised Nutrition Europe (formerly IDACE). Vitamin D Structure • Derived from a steroid • Seco-steroid because one ring is broken • Two forms – D2 ergocalciferol – D3 cholecalciferol Dietary Vitamin D Dietary source Quantity Vitamin D (µg) Egg 1 egg 0.9 Liver* (lamb) 100g 0.9 Kidney* (Lamb) 100g 0.6 Salmon 200g 16 Mackrel 200g 18 Sardines (in oil) 100g 5 Supermilk 200ml 2 Kellog’s Cornflakes 35g 0 Kellog’s Special K 35g 2.5 500 ml 5.5 – 7.5 Infant formula Vitamin D Synthesis 7-dehydrocholesterol ProD3 PreD3 Dietary Vitamin D absorbed from micelles by passive diffusion, transported in chylomicrons Vitamin D3 SKIN UVB Diet D3 and D2 25-hydroxyvitamin D 25(OH)D PTH (+) D3 1,25-dihydroxyvitamin D (+) low PO 2/4 + DBP 1,25(OH)2D Increase calcium and phosphorus absorption Mobilise calcium stores Maintain serum calcium and phosphorus Metabolic functions Bone health Neuromuscular functions Vitamin D Status in Ireland 75·6 % <75 nmol/L % Population 25-hydroxyvitamin D = biomarker of vitamin D status 50 40·1 % 40 30 21·9 % 20 10 6·7 % 0 <30 nmol/L Disagreement over cut offs <40 nmol/L <50 nmol/L Cashman KD, et al. Br J Nutr 2012;10:1-9. Vitamin D Metabolism Vitamin D (cholecaiferol) PTH secreted in response to low calcium increases the action of 1hydroxylase Liver Kidney 1-25dihydroxy vitamin D inhibits it’s own synthesis and increases formation of 24-hydroxy calcidiol Ergocalciferol (D2) undergoes the same metabolism The Nutrition Society Textbook Series, Introduction to Human Nutrition, Second Edition © 2009, 2002 Summary of Vitamin D Metabolism 7-dehydrocholesterol Vitamin D3 25-hydroxyvitamin D3 1,25-hydroxyvitamin D3 What factors might impact status? Season Latitude > 40o N/S Skin Dietary intake 1 µg = 40 IU Vitamin D and Calcium Homeostasis ↑ reabsorption in the kidney ↑ intestinal absorption ↑ mobilisation of bone mineral DeLuca H F Am J Clin Nutr 2004;80:1689S-1696S Vitamin D Metabolic Function • Maintain concentrations of calcium: – increase intestinal absorption of calcium – reduce excretion of calcium – mobilisation of bone mineral • Important for bone health Vitamin D Deficiency • Rickets – Bones fail to calcify normally • Bones bend – Affects children • Osteomalacia – Poor mineralization of bones – Results from demineralization – Affects adults – Bones are soft, flexible, brittle, and deformed – Women and older people Dose-response relation between serum 25-hydroxyvitamin D concentrations and all-cause mortality (A), cardiovascular mortality (B), and cancer mortality (C) in 9578 subjects. Schöttker B et al. Am J Clin Nutr 2013;97:782-793 25(OH)D <30 nmol/L = 1.7 increased risk of death Vitamin D: Other Functions • Cell differentiation – Immune cells • Immune function – Osteoclasts • Activated immune cells express VDR – Skin cells • Enhance antibody synthesis • β-cell function – Insulin secretion and sensitivity – Potential to improve glucose control • Regulates production of cytokines Vitamin D Requirements Infants Adolescents Adults 400 IU (10 μg) 600 IU (15 μg) 400 IU (10 μg) RDA Mandatory supplementation in Irish Infants 5µg • 5 – 15 minutes sun exposure daily – Depends on skin type, latitude and season – E.g. Average skin type, noon, Miami, summer approximately 6 minutes = 1000 IU 40 IU = 1 μg Vitamin D Toxicity • Toxicity results in raised blood calcium levels – Increase blood pressure – Calcification of soft tissue • Threshold unknown – Adults taking supplements >250 μg/day – Infants > 50 μg/day – US UL 100 μg • Excess exposure to sunlight does NOT cause toxicity – Sunlight max 20,000 IU, 100 to 200 nmol/L 25OHD Example: NANS Vitamin D Example: NANS Vitamin D March to September Example: NANS Vitamin D % of the population in different ranges of plasma Vitamin D at different times of the year Threshold All year Winter Summer < 30 nmol < 40 nmol < 50 nmol 6.7 21.9 40.1 11.1 31.1 55.0 3.4 15.4 28.9 Example: NANS Vitamin D Plasma Vitamin D Quartiles and Metabolic Syndrome Q1 Q2 Q3 Q4 34 49 66 94 13 11 11 7 Plasma TAG (mmol/l) 1.39 1.26 1.27 1.10 Plasma glucose (mmol/l) 5.36 5.29 5.35 4.98 Plasma vitamin D nmol/L % > 3 MS factors Vitamin D Summary • Calcium homeostasis • Role in cell differentiation, immune system function and Beta-cell function • Important relationship with metabolic health • Food sources and sunlight • Discussion over status cut offs and dietary requirements 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