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Biological value (BV) is a measure of the proportion of absorbed protein from a food which becomes incorporated into the proteins of the organism's body. It captures how readily the digested protein can be used in protein synthesis in the cells of the organism. Proteins are the major source of nitrogen in food. BV assumes protein is the only source of nitrogen and measures the proportion of this nitrogen absorbed by the body which is then excreted. The remainder must have been incorporated into the proteins of the organisms body. A ratio of nitrogen incorporated into the body over nitrogen absorbed gives a measure of protein 'usability' - the BV. Unlike some measures of protein usability, biological value does not take into account how readily the protein can be digested and absorbed (largely by the small intestine). This is reflected in the experimental methods used to determine BV. BV uses two similar scales: #The true percentage utilization (usually shown with a percent symbol). #The percentage utilization relative to a readily utilizable protein source, often egg (usually shown as unitless). These two values will be similar but not identical. The BV of a food varies greatly, and depends on a wide variety of factors. In particular the BV value of a food varies depending on its preparation and the recent diet of the organism. This makes reliable determination of BV difficult and of limited use — fasting prior to testing is universally required in order to ascertain reliable figures. BV is commonly used in nutrition science in many mammalian organisms, and is a relevant measure in humans.〔Thomas, K. Über die biologische Wertigkeit der stickstoff-substanzen in 1909 verschiedenen Nahrungsmitteln. Arch. Physiol., 219.〕 It is a popular guideline in bodybuilding in protein choice.〔Optimum Sports Nutrition: Your Competitive Edge, A Complete Nutritional Guide For Optimizing Athletic Performance; Chapter 12. by Dr. Michael Colgan〕〔(The Great Animal Versus Vegetable Protein Debate What Is The Best Protein For Muscle Growth? )〕 ==Determination of BV== For accurate determination of BV:〔Mitchell, H.H. (1923). ''"(A Method of Determining the Biological Value of Protein )"''. Journal of Biol. Chem. 58 (3): 873.〕 #the test organism must only consume the protein or mixture of proteins of interest (the test diet). #the test diet must contain no non-protein sources of nitrogen. #the test diet must be of suitable content and quantity to avoid use of the protein primarily as an energy source. These conditions mean the tests are typically carried out over the course of over one week with strict diet control. Fasting prior to testing helps produce consistency between subjects (it removes recent diet as a variable). There are two scales on which BV is measured; percentage utilization and relative utilization. By convention percentage BV has a percent sign (%) suffix and relative BV has no unit. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「biological value」の詳細全文を読む スポンサード リンク
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