Historical Overview of the Evidence Used for Setting Protein Requirements for the Japanese Population

Author(s): Tatsuya Koyama

The aim of this study was to describe the transition in the evidence of digestibility for setting the protein requirement in the Japanese population. Evidence cited by the Recommended Dietary Allowances for Japanese (RDAs-J) third, fourth, fifth and sixth revisions and Dietary Reference Intakes in Japan (DRIs-J) 2005, 2010, 2015, and 2020 editions was searched and assessed. From the RDAs-J third revision to the fifth revision, the relative utilization of high-quality protein was used instead of digestibility to correct the results of nitrogen balance studies. From the RDAs-J sixth revision to the DRIs-J 2015 edition, digestibility of mixed proteins was used to correct the results of nitrogen balance studies. Digestibility was set to 90% by quoting experimental results that used a practical diet based on the National Nutrition Survey of 1975 and 1982. Although DRIs-J 2020 also uses digestibility to correct the results of nitrogen balance studies, it quotes only the results of experiments that used mixed proteins on the basis the results of the National Nutrition Survey in 1982 and set the digestibility at 90%. In conclusion, when setting protein requirements for the Japanese population, digestibility has remained the same (90%) since the RDAs-J, sixth revision, that was established in 1999.