The bioavailability of polyphenols following acute consumption of pigmented barley and wheat

Abstract

Polyphenols from pigmented cereal grains exert health-promoting effects but data on their bioavailability are limited. This study investigated the acute bioavailability of polyphenols from the consumption of pigmented whole grain cereal porridges, including purple barley (PB), purple wheat (PW), and blue wheat (BW), compared to a non-pigmented regular wheat (RW). A secondary objective was to assess their effects on plasma antioxidant and inflammatory status postprandially. Phenolic characterisation and antioxidant profiling were performed on extracts from the cooked cereals. Three healthy individuals consumed 200 g of a cereal in a 4-way crossover trial with a one-week washout in between meals. Blood samples were collected at fasting baseline, 30 minutes, 1 hour, 2 hours and 4 hours postprandially. Urine samples were collected at fasting baseline and the 4-hour time point. Pigmented grains exhibited significantly higher phenolic content and antioxidant capacity (p < 0.001) compared to RW. This suggests that pigmented grains may be a better source of polyphenols and potentially offer greater health benefits. However, polyphenol bioavailability following pigmented grain consumption was reduced (less than 6%), suggesting that a substantial fraction remained unabsorbed. The bioavailable phenolic compounds detected included phenolic acids (protocatechuic and caffeic acid), hippuric acid and other phenolic metabolites. Interpersonal variability and the type of grain consumed had an impact on the absorption and excretion of phenolic acids. Only PW consumption resulted in significant (p < 0.01) increases in plasma antioxidant status but no short-term impact on the inflammatory status. This study provides valuable insights into the complex dynamics of polyphenol bioavailability from pigmented cereal consumption and warrants further investigation.