Writing in the Journal of Pharmaceutical and Biomedical earlier this month, researchers were surprised by the level of pharmaceuticals detected in supposedly clean blood batches—in particular, the concentrations of cough medicine and anti-anxiety medication.

The testing also revealed that all 18 batches of blood contained caffeine, suggesting America’s love of coffee, tea and other caffeinated beverages runs deep.

The purpose of the exercise was to find out the purity of the blood samples before they were used to test a method for examining the effect of botanicals on drug metabolization. Botanicals are plants or plant extracts taken for medical or therapeutic reasons, such as echinacea, CBD oil and ginko.