The effect was assessed of the N-methylxanthines: caffeine, theophylline, and theobromine, commonly consumed with the diet, on the emulsification of butter lipids and bioavailability thereof under the in vitro simulated conditions of human stomach and intestines. The research material was farmhouse butter containing a 40 µmol/1g addition of the tested compounds. Based on the results obtained, it was found that, in the dose analyzed, each of the alkaloids intensified the process of forming the emulsion by increasing the dispersion degree thereof. The power of the pro emulsifying activity of alkaloids depended on the arrangement of methyl groups in a molecule and increased according to the order: 1,3-dimethylxanthine (theophylline) → 1,3,7-thrimethylxanthine (caffeine) → 3,7-dimethylxanthine (theobromine). At the same time, each of the alkaloids significantly reduced the bioavailability of lipids. In the case of theophylline, the amount of fatty acids and glycerol, released from the lipids, decreased by 9% on the average compared to the control sample; in the case of caffeine: by 16%, and as for the theobromine by as much as 27%. The results as indicated above suggest that under the conditions of simulated digestion of lipids in the alimentary canal, the alkaloids must have impacted not only the hydrophobic substrate that stimulated emulsification thereof, but, also, the pancreatic lipase. In the latter case, they partially displaced the pancreatic lipase from the micelle’s surface, and, thereby, reduced its direct contact with the substrate, and effectively inhibited it.