Vitamins nutritional actions

Bender DA (1987) Oestrogens and vitamin Be - actions and interactions. World Review of Nutrition and Dietetics 51, 140-88. 

The nutrient sparing effect of antibiotics may result from reduction or elimination of bacteria competing for consumed and available nutrients. It is also recognized that certain bacteria synthesize vitamins (qv), amino acids (qv), or proteins that may be utilized by the host animal. Support of this mode of action is found in the observed nutritional interactions with subtherapeutic use of antibiotics in animal feeds. Protein concentration and digestibiHty, and amino acid composition of consumed proteins may all influence the magnitude of response to feeding antibiotics. Positive effects appear to be largest... 

Much of the toxicological interest in cyanide relating to mammals has focused on its rapid lethal action. However, its most widely distributed toxicologic problems are due to its toxicity from dietary, industrial, and environmental factors (Way 1981, 1984 Gee 1987 Marrs and Ballantyne 1987 Eisler 1991). Chronic exposure to cyanide is correlated with specific human diseases Nigerian nutritional neuropathy, Leber s optical atrophy, retrobulbar neuritis, pernicious anemia, tobacco amblyopia, cretinism, and ataxic tropical neuropathy (Towill etal. 1978 Way 1981 Sprine etal. 1982 Beminger et al. 1989 Ukhun and Dibie 1989). The effects of chronic cyanide intoxication are confounded by various nutritional factors, such as dietary deficiencies of sulfur-containing amino acids, proteins, and water-soluble vitamins (Way 1981). 

Edgar S. Gordon, "Pantothenic Acid in Human Nutrition," in E. A. Evans, Jr., ed, The Biological Action of the Vitamins, The University of Chicago Press, Chicago, 111., 1942. pp. 136143. 

The possibility of interactions of ozone with other environmental stresses has received relatively little recent attention. Two exceptions are noteworthy, however reports of increased susceptibility to some of the actions of ozone in animals that are deficient in vitamin E or the converse (protection conferred by administration of vitamin E) and observations that exposure to ozone at less than 1.0 ppm reduces activity of the ( tochrome P-450 mixed-function oxidase activity of lungs. Although the implications of these observations are not yet clear, they remind us that nutritional variations or exposure to foreign chemicals that are metabolized by lung mixed-function oxidases may provide bases for unanticipated qualitative or quantitative effects associated with oxidant exposures. 

Peroxide formation has also been observed in multivitamin solutions for parenteral nutrition. Lavoie and co-workers [30] have studied the action of light, air, and composition on the stability of multivitamin formulations, and also total parenteral nutrition (TPN) admixtures containing and not containing vitamins and fatty acids. They analyzed the generation of peroxide in multivitamin solutions and in TPN for adults and neonates. The analysis of multivitamin solutions for enteral use revealed the presence of peroxides at the initial opening of the bottle. The levels were higher in Poly-Vi-Sol (vitamin A, Vitamin D, and vitamin C, vitamin Bb riboflavin, and... 

The combined dehydrogenation and decarboxylation of pyruvate to the acetyl group of acetyl-CoA (Fig. 16-2) requires the sequential action of three different enzymes and five different coenzymes or prosthetic groups—thiamine pyrophosphate (TPP), flavin adenine dinucleotide (FAD), coenzyme A (CoA, sometimes denoted CoA-SH, to emphasize the role of the —SH group), nicotinamide adenine dinucleotide (NAD), and lipoate. Four different vitamins required in human nutrition are vital components of this system thiamine (in TPP), riboflavin (in FAD), niacin (in NAD), and pantothenate (in CoA). We have already described the roles of FAD and NAD as electron carriers (Chapter 13), and we have encountered TPP as the coenzyme of pyruvate decarboxylase (see Fig. 14-13). 

Deficiency syndromes of Zn, Cu, Cr, Se and Mo have occurred in patients on total parenteral nutrition (TPN). There is still much research to be done in assessing the nutritional status of many elements and understanding their metabolism, so that normal dietary intake may be supplemented for health benefits. Table 2 is a summary of the amounts required, the functions and the nutritional (usually dietary) imbalances in humans, where known, of the essential trace elements.31-33 (Note that this summary does not attempt to include imbalances related to environmental toxicology and occupational hazards.) Several trace elements have important functions in the immune system. Some are associated with nucleic acid. Others have structural roles, such as Si in cartilage, F and Zn in bone. They may be parts of vitamins, such as Co in vitamin B12, or hormones, such as iodine in thyroid hormones, Zn and Cr have a role in the synthesis and action of insulin.31-33... 

Increasing evidence indicates that diet/nutrition plays an important role in modulating the action and/or metabolism of a number of chemicals, drugs and environmental pollutants. Nutrients are essential for all fundamental cellular processes. The nutritional status of the affected subject may, therefore, influence cellular susceptibility to the effect of xenobiotics, including those from cigarette smoke. While the precise role of vitamin E in cellular metabolism is not yet clear, the vitamin may protect essential cellular components from the adverse effects of xenobiotics either via a free radical scavenging mechanism or as a component of the cell membrane (10-11). Administration of vitamin E has been shown to lessen the toxicity of a variety of compounds (12-16). 

Vitamins are essential in mammalian physiology because their coenzyme forms are prosthetic groups or cofactors in many enzyme reactions or because they can perform certain specialized functions in the human organism. Vitamin A and its role in the visual process is an example. The biology of vitamins may be examined from the nutritional or biochemical points of view. The former is concerned with minimum daily requirements, dietary sources, bioavailability, and deficiency syndromes. The biochemist looks for structures, functional groups, conversion to coenzymes, mechanisms of action, mode of transport, and storage. Both aspects will be addressed in this chapter, though the emphasis will be on the biochemical properties of vitamins. 

Because of cost, they usually are reserved for premium-priced foods. Many types of tocopherols and associated compounds exist, and understanding of the mode of action is continually improving. The forms that give the most antioxidant protection do not always show the greatest vitamin E nutrition activity.167... 

Pharmacological (druglike) actions at very high levels of intake. This is beyond the scope of nutrition, and involves using compounds that happen to be vitamins for the treatment of diseases other than deficiency disease. 

In addition to its provitamin A role, p - carotene is a radical trapping antioxidant and may be nutritionally important in its own right both as an antioxidant and possibly also through direct actions that are independent of retinoids. Other carotenoids that occur in foods, and circulate in the bloodstream, also have free radical trapping activity, and, hence, potential metabolic significance, whether or not they are metabolic precursors of vitamin A. 

Dowd P, Ham SW, Naganathan S, and Hershiine R (1995) The mechanism of action of vitamin K. Annual Reviews of Nutrition 15, 419-40. 

Bates C (1993) Flair concerted action no 10 statns papers riboflavin. International Journal of Vitamin and Nutrition Research 3,274-7. 

Rohde CM, Manatt M, Clagett-Dame M, and DeLuca HF (1999) Vitamin A antagonizes the action of vitamin D in mts. Journal of Nutrition 129, 2246-50. 

David Bender is a Senior Lecturer in Biochemistry at University College London. He has written seventeen books, as well as numerous chapters and reviews, on various aspects of nutrition and nutritional biochemistry. His research has focused on the interactions between vitamin Bg and estrogens, which has led to the elucidation of the role of vitamin Be in terminating the actions of steroid hormones. He is currently the Editor-in-Chief of Nutrition Research Reviews. 

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