Vitamins : their role in the human body

Foreword xiii Preface xv 1 Historical Events Leading to the Establishment of Vitamins 1 1.1 Introduction 1 1.2 Early studies of nutritionally related diseases 2 1.3 Experiments on formulated diets 6 1.4 Naming of the vitamins 7 Further reading 7 References 7 2 Nutritional Aspects of Vitamins 8 2.1 Defi nition and classifi cation of vitamins 8 2.2 Nutritional vitamin defi ciency 8 2.3 Stability and bioavailability of vitamins 10 2.4 Vitamin requirements 11 Further reading 11 References 11 3 Background Physiology and Functional Anatomy 12 3.1 Movement of solutes across cell membranes and epithelia 13 3.2 The blood–brain, blood–cerebrospinal fl uid and placental barriers 26 3.3 Functional anatomy of the small and large intestine, liver and kidney 29 3.4 Digestion and absorption 36 3.5 Glucose transport 39 3.6 Digestion, absorption and transport of dietary fat 44 3.7 Neural and endocrine communication systems 47 3.8 Structure of bone and its growth and development 55 3.9 Cell proliferation 62 Further reading 64 References 64 4 Background Biochemistry 67 4.1 Major degradation pathways in which B-group vitamins are involved as coenzymes 68 Contents viii Contents 4.2 Amino acid utilization 71 4.3 Defences against free radicals and other reactive species 75 4.4 Haemostasis 76 4.5 Atherosclerosis 80 Further reading 90 References 90 5 Background Immunology 94 5.1 General features of the immune system 94 5.2 Innate immunity 95 5.3 Infl ammation 101 5.4 Acquired immunity 103 5.5 Cytokines 106 5.6 Hypersensitivity 107 5.7 Immune suppression 108 5.8 Neuroendocrine modulation of immune responses 108 Further reading 108 References 108 6 The Genetic Control of Protein Synthesis and its Regulation by Nuclear Hormone Receptors 110 6.1 Functional structure of DNA 110 6.2 Role of RNA in protein synthesis 113 6.3 Gene expression 116 6.4 Mutation and polymorphism 116 6.5 Basal transcription 118 6.6 Regulated transcription 120 6.7 Jun, Fos and the AP-1 complex 125 6.8 Nuclear hormone receptors as regulators of protein synthesis 126 Further reading 131 References 131 7 Vitamin A: Retinoids and Carotenoids 133 7.1 Historical overview 134 7.2 Chemistry and biological functions 134 7.3 Dietary sources 136 7.4 Absorption, transport and metabolism 136 7.5 Nutritional factors that infl uence vitamin A status 150 7.6 The role of vitamin A in vision 151 7.7 Retinoids as regulators of gene expression 155 7.8 Effects of vitamin A on the immune system 171 7.9 Role of vitamin A in bone metabolism and embryonic development 174 7.10 Vitamin A and cancer 176 7.11 Vitamin A defi ciency and toxicity 178 Further reading 180 References 180 Contents ix 8 Vitamin D 188 8.1 Historical overview 189 8.2 Chemistry and biological functions 190 8.3 Dietary sources 191 8.4 Cutaneous synthesis, intestinal absorption, transport and metabolism 191 8.5 Molecular action of the vitamin D hormones 198 8.6 Calcium and phosphate homeostasis 208 8.7 Immunoregulatory properties 218 8.8 Effects of vitamin D on insulin secretion 221 8.9 Vitamin D-related diseases 221 8.10 Therapeutic applications of vitamin D analogues 222 8.11 Toxicity 223 8.12 Dietary requirement 224 Further reading 224 References 224 9 Vitamin E 234 9.1 Historical overview 235 9.2 Chemistry, biopotency and units of activity 235 9.3 Dietary sources 236 9.4 Absorption, transport and delivery to tissues 236 9.5 Antioxidant role 239 9.6 Effect upon the ageing immune responses 240 9.7 Vitamin E and atherosclerosis 241 9.8 Vitamin E defi ciency 247 9.9 Dietary intake 251 Further reading 252 References 252 10 Vitamin K 256 10.1 Historical overview 256 10.2 Chemistry 257 10.3 Dietary sources 258 10.4 Absorption, transport and metabolism 258 10.5 Biochemical and physiological functions 263 10.6 Vitamin K defi ciency 268 Further reading 269 References 269 11 Thiamin (Vitamin B1) 273 11.1 Historical overview 274 11.2 Chemistry and biological activity 274 11.3 Dietary sources and bioavailability 274 11.4 Absorption, transport and metabolism 275 11.5 Biochemical functions 277 11.6 Neurophysiological functions 280 11.7 Vitamin B1 defi ciency 282 x Contents 11.8 Nutritional aspects 286 Further reading 287 References 287 12 Flavins: Ribofl avin, FMN and FAD (Vitamin B2) 289 12.1 Historical overview 289 12.2 Chemistry 290 12.3 Dietary sources and bioavailability 291 12.4 Absorption, transport and metabolism 291 12.5 Biochemical functions 297 12.6 Vitamin B2 defi ciency 298 12.7 Nutritional aspects 298 Further reading 299 References 299 13 Niacin: Nicotinic Acid and Nicotinamide 301 13.1 Historical overview 301 13.2 Chemistry 301 13.3 Dietary sources and bioavailability 302 13.4 Absorption, transport and metabolism 303 13.5 Biochemical functions 306 13.6 Niacin defi ciency 308 13.7 Nutritional aspects 308 Further reading 309 References 309 14 Vitamin B6 310 14.1 Historical overview 310 14.2 Chemistry and biological activity 311 14.3 Dietary sources and bioavailability 311 14.4 Absorption, transport and metabolism 312 14.5 Biochemical functions 315 14.6 Regulation of steroid hormone action 319 14.7 Immune function 320 14.8 Vitamin B6 defi ciency 322 14.9 Nutritional aspects 322 Further reading 323 References 323 15 Pantothenic Acid and Coenzyme A 326 15.1 Historical overview 326 15.2 Chemistry 327 15.3 Dietary sources and bioavailability 327 15.4 Absorption, transport and metabolism 328 15.5 Biochemical functions of coenzyme A and acyl carrier protein in cellular metabolism 330 15.6 Physiological roles of coenzyme A in the modifi cation of proteins 332 Contents xi 15.7 Defi ciency in animals and humans 334 15.8 Dietary intake 334 Further reading 335 References 335 16 Biotin 337 16.1 Historical overview 337 16.2 Chemistry 338 16.3 Dietary sources and bioavailability 338 16.4 Absorption, transport and metabolism 339 16.5 Biochemical and physiological functions 341 16.6 Biotin defi ciency 343 Further reading 345 References 345 17 Folate 347 17.1 Historical overview 348 17.2 Chemistry 348 17.3 Dietary sources and bioavailability 348 17.4 Absorption, transport and metabolism 351 17.5 Biochemical functions 359 17.6 Homocysteine-related occlusive arterial and thrombotic diseases 363 17.7 Folate and neural tube defects 371 17.8 Folate defi ciency 374 17.9 Dietary intake 376 Further reading 376 References 377 18 Vitamin B12 383 18.1 Historical overview 383 18.2 Chemistry 384 18.3 Dietary sources and bioavailability 384 18.4 Absorption, transport and metabolism 385 18.5 Biochemical functions 387 18.6 Vitamin B12 defi ciency 388 18.7 Dietary intake 390 Further reading 391 References 391 19 Vitamin C 393 19.1 Historical overview 394 19.2 Chemistry 394 19.3 Dietary sources and bioavailability 395 19.4 Absorption, transport and metabolism 395 19.5 Effect of ascorbic acid upon absorption of inorganic iron 400 19.6 Inhibition of N-nitroso compound formation 401 19.7 Biochemical and neurochemical functions 403 xii Contents 19.8 Role of ascorbic acid in mesenchymal differentiation 406 19.9 Antioxidant role 407 19.10 Immune function 409 19.11 Vitamin C and cardiovascular disease 412 19.12 Vitamin C defi ciency 414 19.13 Dietary intake 415 Further reading 415 References 415 Abbreviations 421 Glossary 423 Index