Association of IGF-1 content with whole, reduced-fat, and low-fat milk in México

The content of insulin-like growth factor 1 (IGF-1) in bovine milk in México is unknown, and high levels could increase the health risk for adult people who ingest milk. The aim of this study was to determine the level of IGF-1 and its relationship with fat content using liquid chromatography with ion trap as a mass detector in milk marketed in Durango, México. During 18 months we analyzed, three times, six lots chosen randomly of whole, reduced-fat, and low-fat milk of three brands. Each sample was pre-treated using cut-off membranes, digested with trypsin, and subjected to liquid chromatography-mass spectrometry. There was a significant difference in the mean concentration of IGF-1 between the brands and types of milk analyzed (Chi square=34.66; p≤0.005). The correlation analysis revealed a positive exponential association between IGF-1 concentration and the fat content of milk with determination coefficients of 0.950 for brand 1, 0.974 for brand 2, and 0.984 for recombinant bovine growth hormone-free. To the best of our knowledge, this is the first study documenting an association between IGF-1 levels and fat content in milk. The decision to consume a brand with or without fat depends on the milk taste and IGF-1 requirements.