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1. Hilton Deeth says:

   June 19, 2018 at 2:21 pm

   Dear Dr Karl,

   With regard to your article on A1 vs A2 milk, I’d like to draw your attention to a 2017 paper “Identification of bioactive peptides and quantification of b-casomorphin-7 from bovine b-casein A1, A2 and I after ex vivo gastrointestinal digestion” by Tora Asledottir et al. (International Dairy Journal 71 (2017) 98-106. The abstract of that paper is pasted below. It shows that Pro-67 is not part of beta-casomorphin-7 which is the peptide 60-66. Furthermore this peptide is produced from both A1 and A2 variants of beta-casein.

   Abstract: This study investigated whether different genetic variants of b-casein (b-CN) give rise to different
   bioactive peptides during digestion. b-CN was purified from bovine milk of genetic variants A1, A2 and I,
   and digested with human gastrointestinal juices in a static ex vivo model. Mass spectrometry analyses
   revealed that the peptide 60YPFPGPIPN68 was exclusively identified from variants containing proline at
   position 67. Most strikingly, the opioid peptide b-casomorphin-7, 60YPFPGPI66, was identified from both
   variants A1 and A2 after simulated digestion, though with concentration being somewhat higher after
   digestion of the variant A1, compared with variants A2 and I. The peptides 134HLPLP138 and 133LHLPLP138
   were both identified after initial 5 min of duodenal digestion. In conclusion, genetic variation of b-CN
   may affect proteolysis during digestion; however, the release of b-casomorphin-7 (BCM7) does not seem
   to be linked solely to variant A1, as earlier suggested by relevant published literature on in vitro
   digestion.

   Kind regards

   Hilton Deeth
   Emeritus Professor of Food Science
   University of Queensland

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