No genetic causal relationship between tea intake and diabetes: a two-sample Mendelian randomization study

Background: Previous studies have suggested a potential risk-reducing effect of tea intake (TI) on diabetes. However, the specific impacts of TI on different types of diabetes and its underlying mechanisms remain unclear. To further explore this topic, we conducted a comprehensive investigation to assess the causal relationship between TI and various types of diabetes, as well as its effects on blood glucose (Glu) and glycated hemoglobin (HbA1). Methods: We collected genome-wide association study data for TI, diabetes, type 1 diabetes (T1D), type 2 diabetes (T2D), Glu, HbA1, green tea intake, herbal tea intake, and Rooibos tea intake from the IEU database. Subsequently, we performed two-sample Mendelian randomization analysis using the TwoSampleMR package. Results: Our analysis revealed no evidence of a causal relationship between TI and the incidence of diabetes, T1D, blood Glu, HbA1c, or T2D. Similarly, no genetic causal relationship was found between green tea intake and diabetes, T1D, T2D, Glu, or HbA1c. The same applied to herbal tea intake and Rooibos tea intake, as there was no genetic causal link with diabetes, T1D, T2D, Glu, or HbA1c. Conclusion: Based on our findings, there is no indication of a causal relationship between TI and the incidence of all types of diabetes, regardless of the specific tea type. However, to comprehensively understand the potential effects of TI on diabetes incidence, including the quantity and timing of intake, further evaluation through additional Mendelian randomization studies is warranted