Antioxidant Capacity of Non-extractable Polyphenols as a Key Dietary Parameter
Given the role played by unbalanced oxidative status in several chronic diseases, dietary antioxidant capacity (AC) has emerged during the last decade as a parameter marking the quality of diets, showing beneficial correlations with several disease biomarkers and health outcomes. However, most studies exclusively consider the contribution of extractable polyphenols to dietary AC, neglecting that of non-extractable polyphenols (NEPP). There is a validated methodology for determining the AC derived from NEPP in individual foods and beverages as a step towards determining total dietary AC. The results show the important contribution of NEPP to total AC in all food groups and can be used to estimate total dietary AC in different populations. Recently, about half of the total dietary AC in the Spanish diet was shown to be provided by NEPP. Preliminary animal and human studies have also reported NEPP-mediated improvements in oxidative status. Overall, the data presented here show that NEPP are important dietary antioxidants that should be considered when estimating total dietary AC or when designing clinical trials involving oxidative status.