Curcumin use by patients and healthy individuals A critical examination of different formulations and their pharmacokinetics

This thesis critically examines curcumin’s pharmacokinetics and bioavailability across various formulations in both patients and healthy individuals. A validated HPLC-MS/MS method (Chapter 2) was developed to quantify curcumin and its metabolites in human plasma, urine, and feces, distinguishing unconjugated from total (unconjugated + conjugated) curcumin. An observational study (Chapter 3) assessed plasma levels in 47 participants using different curcumin formulations. Despite daily intake, plasma concentrations remained nearly 1000 times lower than those required for systemic effects as assessed in in vitro experiments. Even with piperine as an absorption enhancer, bioavailability did not significantly improve. These results showed that curcumin undergoes rapid metabolism, limiting its systemic availability. A controlled intervention study (Chapter 4) tested five commercial curcumin formulations in healthy individuals. Despite high doses and advanced formulations, systemic exposure was minimal due to rapid metabolism and fecal excretion. A lipid-based formulation showed better absorption, however unconjugated curcumin levels remained insufficient for systemic benefits. Given curcumin’s poor systemic bioavailability, Chapter 5 investigated its effects on the gut microbiome in patients with Crohn’s disease and ulcerative colitis. While temporary microbiome shifts were observed, they were not sustained, and clinical parameters remained unchanged.
This thesis refutes the idea that curcumin provides systemic health benefits. While potential indirect effects via the microbiome exist, any local impact is subtle and not sustained. The findings caution against curcumin supplementation, as its widely promoted health claims lack scientific support. Consumers should be aware that curcumin’s purported benefits are not backed by our research, highlighting the need for realistic expectations regarding its efficacy.