ABSTRACT

This study investigates the causal relationship between coffee consumption patterns, propionic acid-producing gut microbiota, and glycated haemoglobin (HbA1c) levels using Mendelian randomisation (MR). Genome-wide association study datasets from the UK Biobank and MiBioGen consortium were analysed, identifying a significant mediating pathway: unsweetened filter coffee consumption promotes Veillonella abundance, which in turn reduces HbA1c levels. The inverse variance weighted method served as the primary analytical approach, supported by sensitivity analyses to ensure robustness. These findings highlight the potential of unsweetened filter coffee as a dietary intervention to improve glycaemic control by modulating gut microbiota. This research provides novel insights into the coffee-intestinal microbiota-metabolism axis and offers practical guidance for diabetes management, emphasising the importance of coffee preparation methods and dietary habits in harnessing its therapeutic potential.

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