These elements are the subject of exciting research in animals, particularly ruminants, where they have been shown to be essential in one or more species. For example, ruminants feeding on grass grown in soil where molybdenum levels are abnormally high have demonstrated an increased tendency to exhibit copper deficiency.
However, for many of these new trace elements, such as manganese, there is no evidence at the present time that abnormally low or high dietary intakes cause substantial nutritional problems in human populations. In earlier expert-consultations, 12 to 20 experts in various aspects of the subject were invited to prepare background papers and to attend the expert committee or consultation 1 in their individual capacity.
Normally there was no meeting prior to the committee meeting or consultation itself. In contrast, the preparation for the consultation entailed a series of preliminary gatherings at which the specific problems could be dealt with by those expert in that field and a solution sought.
Normally, the review process was accomplished through a standing Expert Committee, a body established by the FAO Conference on a periodic basis, but later reliance rested with the less formal Expert Consultation. The decision to conduct an expert committee or expert consultation on a particular nutrient or group of nutrients is usually based on the perceived need, both in terms of the new scientific information available for consideration and in terms of the public health problems associated with the nutrient or nutrients.
Normally one consultation is held in a biennium.
Regarding this particular expert consultation, in August the three organizations convened an expert advisory group with the charge of considering the content and format of the report and recommending an action plan for its implementation. That group included five scientists from both developing and developed countries and a representative of the secretariat. The group agreed on the contents and the organization of the consultation and its report and proposed coordinators who would be responsible for individual chapters while drawing upon inputs from solicited contributors.
It was recognized that the value of the final document would depend on the applicability of its recommendations to a large variety of nutritional situations and cultures; thus contributions from scientists of many different backgrounds were needed. For most of the chapters communication between contributors and coordinators was by correspondence, but for the chapters on copper, zinc and selenium personal contact was considered necessary. For these elements small workshops were convened in Washington, D.
A subsequent informal gathering of the Expert Advisory Group and most of the coordinators was held in August in Tokyo, taking advantage of the meeting of the International Society on Trace Element Research in Humans. The consensus reached at this informal meeting, findings of the workshops and contributions by correspondence were incorporated into the draft chapters, which were examined and discussed at a meeting of the Expert Advisory Group and coordinators of most the chapters in Geneva in October The participants agreed on content, style and format and on a timetable for submission of the revised drafts, and recommended an editor to consolidate the chapters.
Varying knowledge for particular elements Because of the vast differences in knowledge of dietary intakes, metabolism and requirements, the quality of the data bases upon which the final decisions regarding requirements must be made varies substantially among the individual elements.
For example, there is an impressive amount of data relating different levels of intake to deficiency, adequacy and toxicity of selenium. In contrast, there is only indirect and often fragmentary evidence for other trace elements. Homeostasis of different elements is maintained by different means, and the mechanisms regulating absorption of excretion in response to changes in nutritional status are poorly quantified. Yet these mechanisms, together with hundreds of dietary interactions affecting biological availability, have a profound effect on dietary requirements. Whenever the experts lacked exact data to make a strict statistical derivation of requirements, common sense and consensus after extensive discussion produced a final recommendation.
Concepts and definitions Considerable attention was devoted to definitions e. It was difficult to develop and assimilate some concepts; this occurred most often with the "minor" trace elements for which there was a lack of data.
In addition, information for applying the concepts was not always available for some nutrients. Recommendations for populations In the report, the recommendations are presented in the form of safe ranges of intake for population groups, wherever the available data permit. These ranges do not represent individual requirements but describe the limits of adequacy and safety of the mean intake of whole populations. If the population mean intake falls within these limits, practically all members of that population are considered to have an adequate intake.eaglesflightschoollagos.com/scripts/381/563.php
Trace Elements in Human and Animal Nutrition - Google книги
An understanding of the conceptual framework of the recommendations is imperative to the application of the recommendations. The practical applications and limitations of the information on dietary content and availability of the trace elements were considered. When possible, recommendations were made for acceptable lower and upper limits of mean population intakes. There were some surprising conclusions; for example, the recommended range for chromium was reduced by a factor of several hundred, primarily because of extreme measurement errors in the older laboratory techniques.
The final part of the report presents the recommendations of the experts for future activities. A few recommendations relate to research approaches needed to fill important gaps in our knowledge and in our ability to diagnose marginal states of trace element nutrition. The intention of the remaining recommendations is to increase awareness of the great potential health benefits of intervention programmes for whole populations in which trace element deficiencies, environmental or dietary, have been diagnosed. The conquest of iodine deficiency disorders in many countries Hetzel, and of Keshan disease in China Keshan Disease Research Group, are cited as examples of what can be achieved.
Selenium deficiency and thyroid hormone metabolism. Wendel, ed. Selenium in biology and medicine, p. Berlin, Springer. Arthur, J. Hepatic iodothyronine 5' deiodinase: the role of selenium. FAO Nutr. Meet, Rep. Zinc, K.
Iodine, B. Hetzel and G. Selenium, O. Lead, J. Cadium, K. Arsenic, M. Silicon, E. Lithium, W. Aluminum, A.
Other Elements, F. Soil-Plant-Animal Relationships, W. Each chapter includes references. The complete work, Volume 2 as well as Volume 1, is highly recommended and should form part of the library of any institution engaged in human nutrition or animal husbandry. It is a must reference volume for health scientists dealing with nutrient requirements, specifically for toxicities related to trace element imbalances.
Each library should have their own for ready accessibility and practical application.
Trace Elements in Human and Animal Nutrition
A good publication that stands as a tribute to Professor Underwood and his early pioneering works. We are always looking for ways to improve customer experience on Elsevier. We would like to ask you for a moment of your time to fill in a short questionnaire, at the end of your visit. If you decide to participate, a new browser tab will open so you can complete the survey after you have completed your visit to this website. Thanks in advance for your time. Skip to content. Search for books, journals or webpages All Pages Books Journals.
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