Aspects of Vitamin

Table 38-2 summarizes the key aspects of vitamins needed throughout the body. Most of these vitamins cannot be synthesized within the body and must be ingested from an outside source.76 Eating certain foods on a regular basis will provide the body with an adequate supply of the specific vitamins it needs. Fruits and vegetables, for example, often serve as a source of dietary vitamins. Alternatively, there are myriad vitamin supplements that consumers can purchase and self-administer to insure adequate daily vitamin intake. 

Perhaps the most controversial aspects of vitamins is whether we need to take them and, if so, at what dose Tables 16.5 and 16.6 show the recommended daily allowances (RDAs) for fat- and water-soluble vitamins, respectively. 

N. B. Madsen, S. G. Withers, in Chemical, Biochemical, and Medical Aspects of Vitamin Bs, Pyridoxal Phosphate (D. Dolphin, R. Poulson, O. Avramovic, eds.,) John Wiley Sons, New York, part B (1986) p. 355. 

Halpem, J. Some Mechanistic Aspects of Vitamin Bi2 Coenzyme Depen-... 

One aspect of vitamin B12 deficiency is that it results in the accumulation of W5-methyl-THF. N5-Methyl-THF is synthesized in mammals by an irreversible reaction (as shown above) if it cannot be utilized because of a deficiency of vitamin B12, then it accumulates. This causes a depletion of the other forms of THF, resulting in a deficiency of THF. Megaloblastic anemia (pernicious anemia) is associated with a deficiency of cobalamin... 

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 C deficiency results in an impairment in the hydroxylation of collagen. Properly hydroxylated collagen molecules self-associate to form a triple-helix structure within the cell (Figure 9.83). Collagen that is not hydroxylated and does not form the triple helix is not readily secreted from the cell. Its secretion is impaired. The underhydroxylated collagen tends not to build up in the cell but instead is rapidly degraded. Historically, one confusing aspect of vitamin C research was that the deficiency seemed not to result in an accumulation of abnormal... 

These retinoid receptors must form dimers before they interact with RAREs. RARs must form heterodimers with RXR.S, whereas RXRs may also form homodimers. It appears that the RAREs for the homodimers differ from those for the heterodimers. This implies that they may activate different sets of genes. RXRs also form hetcrodimers with thyroid hormone receptors and vitamin O receptois. increasing their affinity for DNA. Several enzymes whose expression depends on RXR have been found. The available experimental data provide convincing evidence that these proteins are, in fact, nuclear receptors belonging to the steroid/thyroid hormone superfamily. They mediate important aspects of vitamin A function. The existence of proteins that specifically bind retinoic acid substantiates the implication of retinoic acid as a physiological form of vitamin A. 

E. Niki, in Clinical and Nutritional Aspects of Vitamin E (Eds. O. Hayaishi and M. Mino), Elsevier Science Pubhcations, Amsterdam, 1987, pp. 3-13. 

Inorganic and Analytical Aspects of Vitamin C Chemistry CH2OH CH2OH... 

The following are texts which could be used for further reading on vitamin C and related subjects. This is not intended (nor could it be) as an exhaustive list of publications on vitamin C. There is a vast primary literature on all aspects of vitamin C chemistry and biochemistry and also many reviews on the topic. Some of the books listed here will provide detailed references which will allow the reader to get into that literature if required. 

Special mention must be given to Professor Maurice Stacey, CBE, FRS, whose first-hand knowledge of the events surrounding aspects of vitamin C in the 1930s provided us with a fascinating insight into developments and personalities at that time. 

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