Does tea intake increase the risk of anemia? Evidence from a large prospective cohort and Mendelian randomization study

Tea consumption is avoided by some due to concerns about its potential to cause anemia. To clarify this impact, we assessed the association between tea intake and anemia in a Chinese prospective cohort study and by Mendelian randomization (MR). We analyzed associations of tea intake with anemia using data from the baseline (N = 30 085) and three subsequent follow-ups (the first: N = 17 898; the second: N = 10 435; the third: N = 5311) in the Guangzhou Biobank Cohort Study (GBCS). We also assessed the causal effect of tea intake on anemia, hemoglobin (Hgb) and hematocrit (Hct) using two-sample MR with summary statistics from relevant genome-wide association studies and the UK Biobank (N = 447 485). At the baseline, compared with never-drinkers, regular tea drinkers had higher levels of Hgb and Hct and a lower risk of anemia after adjustment for confounders (all P < 0.05; all P for trend <= 0.006). Prospectively, compared with never-drinkers, regular tea drinkers had higher Hgb (g L-1) (beta = 0.69; 95% CI, 0.28 to 1.10; P for trend <0.001) and Hct (%) (beta = 0.30; 95% CI, 0.19 to 0.41; P for trend <0.001), but no significant difference in anemia risk (OR = 0.91; 95% CI, 0.82 to 1.02; P for trend = 0.071). MR analyses showed no association between tea intake and anemia, Hgb and Hct. Through triangulation of evidence using a Chinese cohort and genetics, tea consumption appears unlikely to impact anemia risk.