As mentioned above, the two bile acids glycocholic acid and chenodeoxyglycocholate were significantly increased in PDAC compared to CP in the present study (Figs. 3, 5b). A possible explanation for increased levels of circulating bile acids is tumor growth into the bile duct. Another theory includes bile acid reflux into the pancreas, leading to pancreatitis and eventually malignant cell transformation; a direct carcinogenic effect of bile acids is also possible (Feng and Chen 2016). Bile acid levels in prediagnostic plasma have also been connected to future risk of pancreatic cancer (Mayers et al. 2014), supporting our results and reasoning.