Comparative value of various sources of nonspecific nitrogen for the human

Kies, Constance

doi:10.1021/jf60192a003

Cited by 14 publications

(3 citation statements)

References 12 publications

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“…In addition, nonprotein N contains numerous other nutritional or metabolic compounds that are absorbed during digestion, such as amines (decarboxylated amino acids), several vitamins, alkaloids, and ureides, and have C:N ratios in the same range as amino acids. Further, the role of nonspecific nitrogen such as urea and diammonium citrate can reduce the requirements for specific essential amino acids (Kies, 1974;Korslund, 1974). Thus, there appeared to be no sound basis for exclusion of nonprotein N from Kjeldahl N in the computation of the N:P factor.…”

Section: Tionsmentioning

confidence: 99%

Amino acid composition and nitrogen-to-protein conversion factors for animal and plant foods

Sosulski¹,

Imafidon²

1990

J. Agric. Food Chem.

342

210

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Section: Tionsmentioning

confidence: 99%

Amino acid composition and nitrogen-to-protein conversion factors for animal and plant foods

Sosulski¹,

Imafidon²

1990

J. Agric. Food Chem.

342

210

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“…This concept is highly ambiguous because "protein" and "protein"-related compounds refer to a variety of very different substances considered as a whole but differing in terms of their biochemical and analytical nature ( Figure 1). In particular, "protein" can either refer to specific, purified compounds -the biochemical viewpoint -or to the main function of "protein", that is to provide amino acids -the most nutritionally relevant although other nitrogenous compounds can affect the body nitrogen balance (Kies, 1974). Clearly, the choice between one or several conversion factors depends on the objective.…”

Section: Introduction -625 the Flawed Viewpointmentioning

confidence: 99%

Converting Nitrogen into Protein—Beyond 6.25 and Jones' Factors

Mariotti

Tomé

Mirand³

2008

Critical Reviews in Food Science and Nutrition

993

572

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The protein content in foodstuffs is estimated by multiplying the determined nitrogen content by a nitrogen-to-protein conversion factor. Jones' factors for a series of foodstuffs, including 6.25 as the standard, default conversion factor, have now been used for 75 years. This review provides a brief history of these factors and their underlying paradigm, with an insight into what is meant by "protein." We also review other compelling data on specific conversion factors which may have been overlooked. On the one hand, when 6.25 is used irrespective of the foodstuff, "protein" is simply nitrogen expressed using a different unit and says little about protein (s.s.). On the other hand, conversion factors specific to foodstuffs, such as those provided by Jones, are scientifically flawed. However, the nitrogen:protein ratio does vary according to the foodstuff considered. Therefore, from a scientific point of view, it would be reasonable not to apply current specific factors any longer, but they have continued to be used because scientists fear opening the Pandora's box. But because conversion factors are critical to enabling the simple conversion of determined nitrogen values into protein values and thus accurately evaluating the quantity and the quality of protein in foodstuffs, we propose a set of specific conversion factors for different foodstuffs, together with a default conversion factor (5.6). This would be far more accurate and scientifically sound, and preferable when specifically expressing nitrogen as protein. These factors are of particular importance when "protein" basically means "amino acids," this being the principal nutritional viewpoint.

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“…These values are used to correct the calculated 13 CO 2 production rate arising from oxidation of 13 C-labeled amino acids. (5) It has been claimed that dispensable amino acids (nonspecific nitrogen) may exert a 'sparing effect' (reduction) on the IAA requirement (oxidation), as suggested by some N balance studies using generous intakes of nonspecific nitrogen [33]. Hence, the effects of level and source of nonspecific nitrogen on the oxidation of two IAAs, leucine and phenylalanine, when consumed at limited ('FAO' level) or adequate ('MIT' level) intakes have been evaluated [34].…”

Section: The Tracer Techniquesmentioning

confidence: 99%

Dietary Requirements for Indispensable Amino Acids in Adult Humans: New Concepts, Methods of Estimation, Uncertainties and Challenges

Metges¹,

Petzke²,

Young³

1999

Ann Nutr Metab

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Comparative value of various sources of nonspecific nitrogen for the human

Abstract: Research results suggest that level and source of nonspecific nitrogen intake influence apparent adequacy of dietary protein in general and of specific essential amino acid requirements of humans.

Cited by 14 publications

References 12 publications

Amino acid composition and nitrogen-to-protein conversion factors for animal and plant foods

Amino acid composition and nitrogen-to-protein conversion factors for animal and plant foods

Converting Nitrogen into Protein—Beyond 6.25 and Jones' Factors

Dietary Requirements for Indispensable Amino Acids in Adult Humans: New Concepts, Methods of Estimation, Uncertainties and Challenges

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