The Influence of Food Formulation on Digestive Behavior and Bioavailability of Catechin Polyphenols

Consumption of catechin rich foods is associated with a reduction of chronic disease risks. While promising, poor oral bioavailability of catechins from foods is believed to minimize the potential efficacy of these polyphenols. Many factors are believed to contribute to poor catechin bioavailability including: digestive instability, poor intestinal transport, and rapid metabolism and clearance. In order to better understand how food formulation influences catechin bioavailability, both in vitro and in vivo techniques were applied to pure catechins and tea model systems to investigate specific aspects of human digestion and intestinal absorption. Extracts were formulated with common adjuncts including: fruit juices, creamers and food grade antioxidants. Model beverages were subjected to a two stage in vitro digestion coupled to a Caco-2 culture model to determine digestive stability and accumulation/transport by human intestinal cells. Concurrently, in vivo catechin bioavailability was investigated in a Sprague Dawley rat model. Exposure of catechins to simulated digestive conditions resulted in significant loss of epigallocatechin (EGC) (91%), epigallocatechin-gallate (EGCG) (72%) and epicatechin-gallate (ECG) (60%), compared to epicatechin (EC) (11%) and catechin (C) (7%). Homo-and hetero-dimers of EGCG and EGC were characterized in simulated intestinal juices by LC-MS/MS as digestive products. Addition of ascorbic acid (0.25 mg/mL) and citrus juices (20% (v/v)) were found to enhance digestive recovery of native EGCG (20 to > 70%) and EGC (5 to > 90%). Accumulation of catechins by Caco-2 human intestinal cells was also enhanced by formulation with ascorbic acid and citrus juices primarily due to improved digestive recovery and increased uptake efficiency. Ongoing animal studies suggest that in vivo bioavailability of digestively labile catechins, EGCG and EGC, may be improved by formulation with ascorbic acid relative to controls. These data provide evidence that formulation factors impact digestive recovery and may influence intestinal absorption of catechins in vivo.