Different beta-casein fractions in Icelandic versus Scandinavian cow's milk may influence diabetogenicity of cow's milk in infancy and explain low incidence of insulin-dependent diabetes mellitus in Iceland

Objectives. To compare children with insulin-dependent diabetes mellitus (I DDM) with controls in Iceland regarding their consumption of cow's milk in infancy, and to investigate the beta-casein fractions in Scandinavian and I celandic cow's milk. The A1 variant of beta-casein has been shown to be dia betogenic in animal studies, and suggestions have been made that the B vari ant of beta-casein acts similarly. Differences in the relative proportions of beta-casein fractions might explain the lower incidence of IDDM in Icela nd than in Scandinavia. Methods. A retrospective case-control study on IDDM patients and matching c ontrols was performed in Iceland to compare their diets in infancy. Fifty-f ive children with IDDM born in Iceland over a 16-year period and randomly c ollected controls (n = 165) were recruited to the study. Mothers of the chi ldren answered questions on breastfeeding habits and on when cow's milk pro ducts were introduced. Samples of cow's milk from randomly selected milk ba tches from the largest consumption areas in Iceland and Scandinavia were co llected. The milk samples were freeze-dried and their beta-casein fractions were analyzed using capillary electrophoresis. Results. No significant difference was found between IDDM patients and cont rols in the frequency and duration of breastfeeding or the first introducti on of cow's milk products. The analyses of milk samples showed that the per centage of the A1 and B variants of beta-casein in Icelandic milk was signi ficantly lower than in the milk from the Scandinavian countries. Conclusions. Cow's milk consumption in infancy is not related to IDDM in Ic eland. The lower fraction of A1 and B beta-caseins in Icelandic cow's milk may explain why there is a lower incidence of IDDM in Iceland than in Scand inavia.