In studies on the effects of curcumin on various types of cancers, researchers often observed inhibitory effects only on specific types of cancer. One study attributed the lack of beneficial effects of curcumin on induced lung and breast carcinogenesis in animal models to the poor circulating bioavailability of curcumin. In the same study, the authors substantiated the significant inhibitory effects of topical curcumin on chemically induced tumors in mouse skin. It is generally recognized that the therapeutic effectiveness of curcumin is limited due to its poor absorption from the gastrointestinal tract. Oral doses result in only traces appearing in the blood, with most of the dose being excreted in the feces.
One study evaluated the efficacy of Bioperine®, a standardized extract of black pepper containing the alkaloid, piperine, in enhancing the bioavailability of curcumin in animal models and human volunteers 84 . Piperine is proven to enhance the circulating bioavailability of several drugs and nutrients.
In the animal model study, two identical groups of rats were selected, one group receiving piperine alone (20 mg/kg body weight) or curcumin (2 g/kg) followed by piperine (20 mg/kg). The pharmacokinetic profile was determined for both groups of animals. In the human study, ten healthy male volunteers participated in a randomized crossover trial to determine the comparative bioavailability and pharmacokinetic profile of curcumin (2 g) when given along with piperine (20 mg). The results of these studies are indicated in Figures 1 and 2.