Milk A1 and A2 peptides and diabetes

Nestle Nutr Workshop Ser Pediatr Program. 2011;67:187-95. doi: 10.1159/000325584. Epub 2011 Feb 16.


Food-derived peptides, specifically those derived from milk, may adversely affect health by increasing the risk of insulin-dependent diabetes. This position is based on the relationship of type 1 diabetes (T1D) and the consumption of variants A1 and B β-casein from cow's milk. It appears that β-casomorphin-7 (BCM-7) from β-casein may function as an immunosuppressant and impair tolerance to dietary antigens in the gut immune system, which, in turn, may contribute to the onset of T1D. There are thirteen genetic variants of β-casein in dairy cattle. Among those variants are A1, A2, and B, which are also found in human milk. The amino acid sequences of β-casomorphins among these bovine variants and those found in human milk are similar, often differing only by a single amino acid. In vitro studies indicate BCM-7 can be produced from A1 and B during typical digestive processes; however, BCM-7 is not a product of A2 digestion. Evidence from several epidemiological studies and animal models does not support the association of milk proteins, even proteins in breast milk, and the development of T1D. Ecological data, primarily based on A1/ A2 variations among livestock breeds, do not demonstrate causation, even among countries where there is considerable dairy consumption.

Publication types

  • Review

MeSH terms

  • Animals
  • Caseins / genetics*
  • Caseins / immunology
  • Cattle
  • Diabetes Mellitus, Type 1 / etiology*
  • Genetic Variation*
  • Humans
  • Milk / adverse effects
  • Milk / chemistry*
  • Milk / immunology
  • Peptide Fragments / genetics*
  • Peptide Fragments / immunology


  • Caseins
  • Peptide Fragments