Anthocyanin pigments and associated flavonoids have demonstrated ability to protect against a myriad of human diseases, yet they have been notoriously difficult to study with regard to human health. Anthocyanins frequently interact with other phytochemicals to potentiate biological effects, thus contributions from individual components are difficult to decipher. The complex, multicomponent structure of compounds in a bioactive mixture and the degradation of flavonoids during harsh extraction procedures obscure the precise assignment of bioactivity to individual pigments. Extensive metabolic breakdown after ingestion complicates tracking of anthocyanins to assess absorption, bioavailability, and accumulation in various organs. Anthocyanin pigments and other flavonoids that are uniformly, predictably produced in rigorously controlled plant cell culture systems can be a great advantage for health and nutrition research because they are quickly, easily isolated, lack interferences found in whole fruits, can be elicited to provoke rapid and prolific accumulation, and are amenable to biolabeling so that metabolic fate can be investigated after ingestion.

This review considers the bioavailability of health-protective anthocyanin pigments from foods, in light of the multiple molecular structures and complicated traffic patterns taken by anthocyanins both as flavonoid metabolites and as phenolic acid metabolites within the body. Anthocyanins have generally been considered to have notoriously poor bioavailability, based on the very low levels typically detected in routine human blood draws after ingestion. Although some investigations have assessed anthocyanin bioavailability solely based on the measurement of parent anthocyanins or phenolic acid breakdown products, more recent research has increasingly revealed the presence, qualitative diversity, relatively high concentrations, and tenacity of molecular intermediates of anthocyanins that retain the unique flavonoid C6-C3-C6 backbone structure. We argue that the persistence of anthocyanin metabolites suggests enterohepatic recycling, leading to prolonged residence time, and supports the notion that anthocyanins are far more bioavailable than previously suggested.