Approved research

The association between milk and dairy products and the risk of major diseases and all-cause mortality: a Mendelian randomisation study using UK Biobank

Lay summary

The association between milk and dairy products and a range of chronic diseases remains inconclusive, as most of the previous studies were done using observational study designs with the possibility of residual confounding and/or reverse causation. Large-scale randomised trial is lacking to address this question so far. Here we propose to access the UK Biobank and use the Mendelian randomisation design to indirectly infer causality among milk and dairy products and a range of chronic diseases. The genotypes of C/T 13910 and G/A 22018 located in the MCM6 gene (upstream from the lactase gene) affect the transcription of the lactase enzyme and thereby affect the ability to digest milk and dairy products. Individuals with lactose intolerance (CC-13910 and GG-22018) may have serious symptoms after milk intake, and they are recommended to avoid milk or dairy products. The Mendelian randomisation design enables us to use the genetic variants as a proxy for the long-term differences in milk and dairy product intake, thereby largely avoiding confounding and reverse causation. By accessing the UK biobank and using the whole cohort we can explore the causal association between the genotypes of C/T 13910 and G/A 22018 and the risk of obesity, type 2 diabetes, cardiovascular disease, osteoporosis, and cancer as well as all-cause mortality. This study is, to our best knowledge, the largest population-based study to explore the causal association between milk and dairy intake and a range of chronic diseases using Mendelian randomisation study design. The results will provide adequate evidence whether high dairy/milk intake is associated with a range of chronic diseases. Such information will be important for the general consumers about the health consequences of eating dairy products.