Genetically predicted milk consumption and bone health, ischemic heart disease and type 2 diabetes: a Mendelian randomization study

• Published in: European journal of clinical nutrition 2017-08, Vol.71 (8), p.1008-1012
• Main Authors: Yang, Q, Lin, S L, Au Yeung, S L, Kwok, M K, Xu, L, Leung, G M, Schooling, C M
• Format: Article
• Language: English
• Subjects: 692/308/174; 692/700/478/174; Adipose tissue; Adiposity; Adult; Animals; Biocompatibility; Biomedical materials; Body mass; Body Mass Index; Body size; Bone Density; Bone mineral density; Cardiovascular disease; Cardiovascular diseases; Case-Control Studies; Chronic diseases; Clinical Nutrition; Color; Confidence intervals; Consumption; Coronary artery disease; Diabetes; Diabetes mellitus; Diabetes mellitus (non-insulin dependent); Diabetes Mellitus, Type 2 - genetics; Diabetes Mellitus, Type 2 - prevention & control; Epidemiology; Europe; Eye; Fasting; Female; Food Preferences; Genetic analysis; Genetic Association Studies; Genetic diversity; Genetic Predisposition to Disease; Genetic variance; Health aspects; Health risk assessment; Heart; Heart diseases; Human nutrition; Humans; Insulin; Internal Medicine; Ischemia; Laboratory testing; Lactase; Lipids; Male; Medical research; Medicine; Medicine & Public Health; Mendelian Randomization Analysis; Metabolic Diseases; Micronutrients; Milk; Milk - adverse effects; Minichromosome Maintenance Complex Component 6 - genetics; Myocardial Ischemia - genetics; Myocardial Ischemia - prevention & control; Nutrition research; original-article; Osteoporosis; Osteoporosis - genetics; Osteoporosis - prevention & control; Overweight - etiology; Overweight - genetics; Polymorphism, Single Nucleotide; Prevention; Public Health; Randomization
• ISSN: 0954-3007; 1476-5640
• DOI: 10.1038/ejcn.2017.8

Background/objectives: Milk provides protein and micronutrients, and is recommended by some dietary guidelines, particularly for bone health. Meta-analysis of small randomized controlled trials suggests that milk may increase bone mineral density, but they are very heterogeneous. No randomized controlled trial has assessed the effects of milk on major chronic diseases. Previous Mendelian randomization studies of milk did not consider bone health, found no effects on ischemic heart disease (IHD) or type 2 diabetes (T2D) but higher body mass index. Using larger genetic studies, we estimated the effects of milk on osteoporosis, IHD, T2D, adiposity, lipids and glycemic traits. Subjects/methods: Instrumental variable analysis based on a genetic variant endowing lactase persistence (rs4988235 ( MCM6 )) was used to obtain estimates for osteoporosis (GEFOS), IHD (CARDIoGRAMplusC4D), T2D (DIAGRAM), adiposity (GIANT), lipids (GLGC) and glycaemic traits (MAGIC). Eye color was a negative control for IHD, as it mirrors the distribution of lactase persistence and IHD in Western Europe. Results: Genetically predicted adult milk consumption was not clearly associated with bone mineral density, IHD (odds ratio (OR): 1.03 per s.d., 95% confidence interval (CI): 0.95–1.12) and or T2D (OR: 0.92, 95% CI: 0.83–1.02) but was associated with higher log-transformed fasting insulin (0.05, 95% CI: 0.02–0.07) and body mass index (0.06, 95% CI: 0.03–0.09). Genetically predicted eye color was not associated with IHD. Conclusions: The lack of association of genetically predicted milk consumption with bone health, IHD or T2D suggests few beneficial effects but is more consistent with milk promoting adiposity.