arising from K. Luo et al. Nature Metabolism https://doi.org/10.1038/s42255-023-00961-1 (2024)

In the 2024 January issue of Nature Metabolism, Luo et al.¹ reported an inverse association between milk intake and risk of type 2 diabetes (T2D) among individuals who were lactase non-persistent (LNP), as determined by the lactase (LCT) rs4988235 homozygous GG genotype. The authors also reported inverse cross-sectional associations of milk intake with several T2D-related metabolic traits, including body mass index (BMI) and waist circumference (WC) in LNP individuals. However, in their analyses, no adjustments for BMI/WC were done in assessing the association between milk intake and T2D risk, which may lead to biased results. Given the established causal relevance of adiposity for incident T2D^2,3 and the observed inverse associations of milk intake with adiposity in the study population, it is therefore important to establish whether the associations of milk consumption, milk-associated gut bacteria and milk-associated metabolites with T2D risk are confounded, or mediated, by BMI/WC in the paper by Luo et al.