Causal relationship between tea intake and bone mineral density at different ages ̶ A Mendelian randomization study.

Introduction: bone mineral density (BMD) is strongly associated with the risk of osteoporosis and fractures. Furthermore, dietary tea consumption also has a great impact on the variation in BMD. The pathway mechanisms from tea consumption to BMD are not well known. Therefore, we applied a two-sample Mendelian randomization (MR) approach in an attempt to explore the causality between tea consumption and BMD. And then examine whether the effects of tea intake on BMD are specific across different age groups. Methods: we investigated the relationship between tea consumption and BMD using a two-sample Mendelian randomization analysis, utilizing 31 single nucleotide polymorphisms (SNPs) related to tea intake from pooled data from a gene-wide association study (GWAS) of 447,485 British Biobank of European Origin participants, with BMD derived from a meta-analysis of total body BMD and age-specific effects in the Lifelong Genetic Cohort Study (n = 66,628). Causal analysis between tea intake and BMD was performed using MR-Egger, inverse variance weighting (IVW), weighted median, and weighted mode. Results: in IVW, tea consumption has a positive causal effect on total body BMD. However, in different age groups, BMD has a positive effect only within the 45-60-year group. There is no genetic pleiotropy effect of tea intake can have an effect on systemic BMD or among the five different age groups. The Cochran Q statistic and MR-Egger regression were applied to calculate heterogeneity in the IVW method, and no significant heterogeneity was indicated. Conclusions: the results of the MR analysis showed a positive causal effect of tea intake on total body BMD, whereas among the different age groups, tea intake positively affected BMD only in the 45-60 age group, which implies that tea is beneficial in maintaining or increasing BMD in this age group and may reduce osteoporosis and fracture risk.