Serafini M.Research Center on Agriculture (CRA), Rome, Italy.
Clinical and epidemiological studies have shown that oxidative stress (OS) plays a significant role in the development of degenerative and chronic inflammatory diseases.
Human body developed a sophisticated and co-operative array of antioxidant defenses to protect cellular district from OS. Despite the high grade of complexity and efficiency of endogenous defenses, the mechanism is not infallible and there is a need to optimize redox machinery with diet.
Food items rich in antioxidants such as tea, coffee and chocolatehave been accredited of an antioxidant action in vivo. However, the extent to which these foods are able to tune oxidative stress and the identification of the exogenous molecules involved is unclear and it represents a fundamental matter of debate.
Flavonoids are able to scavenge oxygen and nitrogen derived free radicals, modulating antioxidant enzymes, cellular redox transcription factors such as Nuclear Factor kB and to contribute to the in vitro antioxidant potential of plant foods.
However, the in vitro evidence might be somehow of limited impact due to the non-physiological concentrations utilized and to their low degree of absorption. Moreover, their extensive metabolism within the body, leading to molecules with different chemical structure and activity compared to the ones originally present in the food, have raised concerns about their antioxidant action in humans.
The first two systematic reviews of dietary intervention studies with flavonoids-rich foods on markers of antioxidant function and oxidative stress will be presented, with special focus on the activity of coffee, tea and chocolate.
There is a strong need of increasing the existing knowledge on the real efficacy of antioxidants in vivo in order to clarify if dietary flavonoids from tea, cocoa and coffee are active red-ox ingredients or just ancillary “travellers” of plant food- based diets.