Plasma concentrations of curcumin in individuals using curcumin with adjuvants or lipid formulated curcumin supplements: a real world cohort

The spice curcumin and its metabolites have been linked to many beneficial health effects. These effects have, thus far, not been duplicated in independent research most likely due to low plasma concentrations of curcumin. Despite the many reports, the publics interest in curcumin continues to grow and many people use curcumin in daily life. Moreover, companies seize the popularity of curcumin and claim that their formulations increase systemic expose of curcumin. In this independent study we determined the plasma concentration of curcumin after oral intake in daily life to determine if the systemic exposure is sufficient to achieve beneficial health effects. We used a validated HPLC-MS/MS assay to determine the plasma concentration of curcumin and its metabolites in 47 individuals (patient or healthy) using their own curcumin formulations. Through questionnaires, we assessed which other supplements and (self-)medication(s) were used. The concentrations of curcumin and its metabolites were analyzed in plasma samples collected just before and 1.5 h after curcumin intake. Each sample was pretreated with and without {beta}-glucuronidase to determine the levels of conjugated and unconjugated curcumin. After oral intake of the curcumin supplement, plasma concentrations of curcumin, demethoxycurcumin, bisdemethoxycurcumin and tetrahydrocurcumin ranged between 2 and 4 nM. Use of adjuvants like piperine did not result in higher curcumin plasma concentrations. Adding {beta}-glucuronidase to the plasma sample increased curcumin plasma levels from below LLQ to 25.3 ng/mL, however still below any plasma concentration to which a beneficial health effect can be expected. The observed plasma concentration of unchanged curcumin remained several orders below the concentration of 2-100 g/mL used in in vitro studies. Therefore, our study confirms the low plasma levels of curcumin and indicates the need to be critical towards the claimed beneficial systemic health effects of current curcumin supplement use in daily life among patients and healthy individuals.