The sources of the vitamines

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  • The principally pharmacological aspects of vitamins are described here.The nutritional aspects, physiological function, sources, daily requirements and deficiency syndromes (primary and secondary) are to be found in any textbook of medicine. • • • • Vitamin A: retinol Vitamin B: complex Vitamin C: ascorbic acid Vitamin D, calcium, parathyroid hormone, calcitonin, bisphosphonates, bone • Treatment of calcium and bone disorders • Vitamin E:tocopherol that subclinical vitamin deficiencies are a cause of much chronic ill-health and liability to infections.

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  • Dietary Sources The retinol activity equivalent (RAE) is used to express the vitamin A value of food. One RAE is defined as 1 µg of retinol (0.003491 mmol), 12 µg of βcarotene, and 24 µg of other provitamin A carotenoids. In older literature, vitamin A was often expressed in international units (IU), with 1 RAE being equal to 3.33 IU of retinol and 20 IU of β-carotene, but these units are no longer in current scientific use. Liver, fish, and eggs are excellent food sources for preformed vitamin A; vegetable sources of provitamin A carotenoids include dark green and deeply colored...

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  • Thiamine (Vitamin B1) Thiamine was the first B vitamin to be identified and is therefore also referred to as vitamin B1. Thiamine functions in the decarboxylation of αketoacids, such as pyruvate α-ketoglutarate, and branched-chain amino acids and thus is a source of energy generation. In addition, thiamine pyrophosphate acts as a coenzyme for a transketolase reaction that mediates the conversion of hexose and pentose phosphates.

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  • The presentation of essential data concerning vitamines to succeeding groups of students has become increasingly difficult with the development of research in this field. The literature itself has assumed a bulk that precludes sending the student to original sources except in those instances when they are themselves to become investigators. The demand on the part of the layman for concise information about the new food factors is increasing and worthy of attention.

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  • The metabolic pathways leading froml-[2-13 C]aspartic acid, [2-13 C]glycine andl-[methyl-13 C]methionine to vitamin B12were investigated, focusing on the biosynthetic pathways leading to the aminopropanol moiety of vita-min B12and on the role of the Shemin pathway leading tod-aminolevulinic acid (a biosynthetic intermediate of tetrapyrrole), by means of feeding experiments with Propionibacterium shermaniiin combination with 13 C-NMR spectroscopy.

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  • This book is for anyone who wants an understanding of the fascinating role vitamins and minerals play in nutrition. It can be used as a supplementary textbook for nutrition classes, as a self-learning guide, and as a refresher for health professionals. This book broadens and explains the vitamin and mineral information found in standard nutrition courses. Throughout the text are many figures, graphs, and tables that visually display information and relationships. If you have not taken a class in biochemistry, then this will be an interesting and relevant way to be introduced to it....

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  • Toxicity The safe upper limit for vitamin B6 has been set at 100 mg/d, although no adverse effects have been associated with high intakes of vitamin B 6 from food sources only. When toxicity occurs, it causes a severe sensory neuropathy, leaving patients unable to walk. Some cases of photosensitivity and dermatitis have also been reported. Folate, Vitamin B12 See Chap. 90. Vitamin C Both ascorbic acid and its oxidized product dehydroascorbic acid are biologically active.

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  • Tham khảo sách 'the vitamine manual', y tế - sức khoẻ, y học thường thức phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả

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  • Biotin Biotin is a water-soluble vitamin that plays a role in gene expression, gluconeogenesis, and fatty acid synthesis and serves as a CO 2 carrier on the surface of both cytosolic and mitochondrial carboxylase enzymes. The vitamin also functions in the catabolism of specific amino acids (e.g., leucine). Excellent food sources of biotin include organ meat such as liver or kidney, soy, beans, yeast, and egg yolks; however, egg white contains the protein avidin, which strongly binds the vitamin and reduces its bioavailability.

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  • Zinc Zinc is an integral component of many metalloenzymes in the body; it is involved in the synthesis and stabilization of proteins, DNA, and RNA and plays a structural role in ribosomes and membranes. Zinc is necessary for the binding of steroid hormone receptors and several other transcription factors to DNA. Zinc is absolutely required for normal spermatogenesis, fetal growth, and embryonic development.

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  • Selenium Selenium, in the form of selenocysteine, is a component of the enzyme glutathione peroxidase, which serves to protect proteins, cell membranes, lipids, and nucleic acids from oxidant molecules. As such, selenium is being actively studied as a chemopreventive agent against certain cancers, such as prostate. Selenocysteine is also found in the deiodinase enzymes, which mediate the deiodination of thyroxine to triiodothyronine (Chap. 335).

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  • A basic premise of the Dietary Guidelines is that food guidance should recommend diets that will provide all  the nutrients needed for growth and health. To this end, food guidance should encourage individuals to achieve  the most recent nutrient intake recommendations of the Institute of Medicine, referred to collectively as the Dietary Reference Intakes (DRIs). Tables of the DRIs are provided at http://www.iom.edu/Object.File/Master/21/372/0.pdf.

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  • The diet is the source of some 40 nutrients for human beings. These classically are divided into energy-yielding dietary components (carbohydrates, fats, and proteins), sources of essential and nonessential amino acids (proteins), essential unsaturated fatty acids (fats), minerals (including trace minerals), and vitamins (water-soluble and fat-soluble organic compounds) (see Shils et al . , 1999).

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  • In the first volume of this two-volume book, Advanced Nutrition: Macronutrients , the needs for the macronutrients were discussed. The absorption, metabolism, excretion, and function of the various sources of energy as well as detailed discussions of the need for water and energy balance were presented. The needs for the micronutrients, as well as explanations of how these nutrients function in the body, were deferred to this, the second volume.

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  • Harrison's Internal Medicine Chapter 57. Photosensitivity and Other Reactions to Light Solar Radiation Sunlight is the most visible and obvious source of comfort in the environment. The sun provides the beneficial effects of warmth and vitamin D synthesis; however, acute and chronic sun exposure also have pathologic consequences. Few effects of sun exposure beyond those affecting the skin have been identified, but cutaneous exposure to sunlight is the major cause of human skin cancer and can exert immunosuppressive effects as well.

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  • Vegetarians of all types can achieve recommended nutrient intakes through careful selection of foods. These individuals should give special attention to their intakes of protein, iron, and vitamin B12, as well as calcium and vitamin D if avoiding milk products. In addition, vegetarians could select only nuts, seeds, and legumes from the meat and beans group, or they could include eggs if so desired. At the 2,000­calorie level, they could choose about 1.5 ounces of nuts and  2 /3 cup legumes instead of 5.

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  • The cone snail is the only invertebrate system in which the vitamin K-dependent carboxylase (orc-carboxylase) and its product c-carboxygluta-mic acid (Gla) have been identified. It remains the sole source of structural information of invertebrate c-carboxylase substrates. Four novel Gla-con-taining peptides were purified from the venom of Conus textileand charac-terized using biochemical methods and mass spectrometry.

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  • This book reveals the little-known sources where you can purchase foods, food ingredients and herbal products that very few people know about and yet are critical for overcoming chronic diseases like diabetes, cancer, heart disease and clinical depression. For example, in this book you’re going to learn about where to buy freeze-dried berries that work as powerful whole food vitamins that will lower cholesterol, fight cancer, enhance immune system function, prevent cardiovascular disease, and provide a long list of other healthful benefits. But that’s only the beginning....

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  • Sunlight is the most visible and obvious source of comfort in the environment. The sun provides the beneficial effects of warmth and vitamin D synthesis; however, acute and chronic sun exposure also have pathologic consequences. Few effects of sun exposure beyond those affecting the skin have been identified, but cutaneous exposure to sunlight is the major cause of human skin cancer and can exert immunosuppressive effects as well. The sun's energy reaching the earth's surface is limited to components of the ultraviolet (UV), the visible, and portions of the infrared spectra. ...

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  • Efforts may be warranted to promote increased dietary intakes of potassium, fiber, and possibly vitamin E, regard­ less of age; increased intakes of calcium and possibly vitamins A (as carotenoids) and C and magnesium by adults; efforts are warranted to increase intakes of calcium and possibly magnesium by children age 9 years or older. Efforts may be especially warranted to improve the dietary intakes of adolescent females in general. Food sources of these nutrients are shown in appendix B.

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