Background Observational studies have reported the association between tea consumption and the risk of lower respiratory tract infections (LRTIs). However, a consensus has yet to be reached, and whether the observed association is driven by confounding factors or reverse causality remains unclear. Method A two-sample Mendelian randomization (MR) analysis was conducted to determine whether genetically predicted tea intake is causally associated with the risk of common LRTI subtypes. Genome-wide association study (GWAS) from UK Biobank was used to identify single-nucleotide polymorphisms (SNPs) associated with an extra cup of tea intake each day. The summary statistics for acute bronchitis, acute bronchiolitis, bronchiectasis, pneumonia, and influenza and pneumonia were derived from the FinnGen project. Results We found that genetically predicted an extra daily cup of tea intake was causally associated with the decreased risk of bronchiectasis [odds ratio (OR) = 0.61, 95% confidence interval (CI) = 0.47–0.78, P < 0.001], pneumonia (OR = 0.90, 95% CI = 0.85–0.96, P = 0.002), influenza and pneumonia (OR = 0.91, 95% CI = 0.85–0.97, P = 0.002), but not with acute bronchitis (OR = 0.91, 95% CI = 0.82–1.01, P = 0.067) and acute bronchiolitis (OR = 0.79, 95% CI = 0.60–1.05, P = 0.100). Sensitivity analyses showed that no heterogeneity and pleiotropy could bias the results. Conclusions Our findings provided new evidence that genetically predicted an extra daily cup of tea intake may causally associated with a decreased risk of bronchiectasis, pneumonia, and influenza and pneumonia. Supplementary Information The online version contains supplementary material available at 10.1007/s00394-022-02994-w.

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