The article "Converting Nitrogen into Protein – Beyond 6.25 and Jones’ Factors" by François Mariotti, Daniel D. Tomé, and Philippe Patureau Mirand critically reviews the traditional method of converting nitrogen content in foodstuffs into protein content using a constant factor of 6.25. This factor, first introduced by Jones in 1941, has been used for 75 years but is scientifically flawed due to the varying nitrogen contents of different proteins and the presence of non-protein nitrogen compounds in foodstuffs. The authors highlight that the nitrogen-to-protein ratio can vary significantly depending on the foodstuff, and specific conversion factors for different protein sources are necessary for accurate estimation. The review discusses various methods to determine specific conversion factors, including amino acid analysis and the calculation of factors based on amino acid sequences. These methods provide more accurate estimates of protein content and amino acid availability compared to the universal factor of 6.25. The authors propose a set of specific conversion factors for different foodstuffs, with an average default factor of 5.6, which they argue is more scientifically sound and accurate. The article concludes by emphasizing the importance of using specific conversion factors to accurately evaluate the quantity and quality of protein in foodstuffs, particularly when "protein" refers to amino acids. The authors hope that their critical review will stimulate further scientific and regulatory discussions on this issue.The article "Converting Nitrogen into Protein – Beyond 6.25 and Jones’ Factors" by François Mariotti, Daniel D. Tomé, and Philippe Patureau Mirand critically reviews the traditional method of converting nitrogen content in foodstuffs into protein content using a constant factor of 6.25. This factor, first introduced by Jones in 1941, has been used for 75 years but is scientifically flawed due to the varying nitrogen contents of different proteins and the presence of non-protein nitrogen compounds in foodstuffs. The authors highlight that the nitrogen-to-protein ratio can vary significantly depending on the foodstuff, and specific conversion factors for different protein sources are necessary for accurate estimation. The review discusses various methods to determine specific conversion factors, including amino acid analysis and the calculation of factors based on amino acid sequences. These methods provide more accurate estimates of protein content and amino acid availability compared to the universal factor of 6.25. The authors propose a set of specific conversion factors for different foodstuffs, with an average default factor of 5.6, which they argue is more scientifically sound and accurate. The article concludes by emphasizing the importance of using specific conversion factors to accurately evaluate the quantity and quality of protein in foodstuffs, particularly when "protein" refers to amino acids. The authors hope that their critical review will stimulate further scientific and regulatory discussions on this issue.