Changes in new version Added section for disclosing conflicts of interest required for PCI_Archaeology submission. Caries ratio recalculated - Downstream effects: caries and calculus (presence/absence) no longer correlated Site-wide caries ratio increased from 12.7% to 17.6% No other relevant changes in values as a result. 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 coffee and smoking of tobacco on an individual scale, which is also confirmed by historic documentation and identification of pipe notches in the dentition. Nicotine and/or cotinine was present in 60% of individuals with at least one visible pipe notch. We find some influence of skeletal preservation on the detection of alkaloids and salicylic acid, with higher quantities of compounds extracted from well-preserved individuals, and also observe a relationship between weight of the calculus sample and raw quantity of the detected compounds, and we were able to detect alkaloids in samples as small as 2 mg. We found correlations between chronic maxillary sinusitis and the presence of multiple ...