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  • 标题:Conversion Ratio of Tryptophan to Niacin in Japanese Women Fed a Purified Diet Conforming to the Japanese Dietary Reference Intakes
  • 本地全文:下载
  • 作者:Tsutomu FUKUWATARI ; Mari OHTA ; Naoko KIMURA
  • 期刊名称:Journal of Nutritional Science and Vitaminology
  • 印刷版ISSN:0301-4800
  • 电子版ISSN:1881-7742
  • 出版年度:2004
  • 卷号:50
  • 期号:6
  • 页码:385-391
  • DOI:10.3177/jnsv.50.385
  • 出版社:Center for Academic Publications Japan
  • 摘要:In order to establish the human requirements of niacin, it is first important to know how much tryptophan is converted to niacin in the human body. In a general, 60mg of tryptophan is equivalent to 1mg of niacin, whereas the conversion ratio of tryptophan to niacin is yet to be confirmed. The aim of this study was to know the conversion ratio of tryptophan to niacin in Japanese females fed a purified diet, which followed the Japanese Dietary Reference Intakes. Ten young Japanese females were housed in the same facility and given the same daily living activity schedule for 7d. The composition of their purified diet was conformed to the Dietary Reference Intakes in Japan. The diet was niacin free. In order to investigate the conversion ratio, daily urinary outputs were collected. Tryptophan-niacin metabolites in the urine were measured and the conversion ratio of tryptophan to niacin calculated. The conversion ratio was calculated by comparing the dietary intake of tryptophan and the sum of the niacin catabolites such as N 1-methylnicotinamide, N 1-methyl-2-pyridone-5-carboxamide, and N 1-methyl-4-pyridone-3-carboxamide, which were derived only from the dietary intake of tryptophan. The ratio was calculated as 1.5±0.1(mean±SE for 10 women; in molar basis) on the last day of the experiment. It was calculated that if the excretory percentage of niacin metabolites in the urine were 60% of the tryptophan ingested, the conversion factor would be a value of 67, meaning that is 67mg of tryptophan is equal to 1mg of niacin.
  • 关键词:conversion ratio;conversion factor;tryptophan-niacin;N1-methylnicotinamide;female human subjects
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