## Abstract Dental calculus is an excellent source of information on the dietary patterns of past populations, including consumption of plant-based items. The detection of plant-derived residues such as alkaloids and their metabolites in dental calculus provides direct evidence of consumption by individuals within a population. We conducted a study on 41 individuals from Middenbeemster, a 19th century rural Dutch archaeological site. Skeletal and dental analysis was performed to explore potential relationships between pathological conditions/lesions and the presence of alkaloids. We also explored other factors potentially affecting the detection of alkaloids, including sample weight and skeletal preservation. Dental calculus was sampled and analysed using ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-ESI-MS/MS). We were able to detect nicotine, cotinine, caffeine, theophylline, and salicylic acid. By detecting these compounds we are able to show the consumption of tea and ...