Oxidative stress (OS) - defined as the imbalance between free radical production and antioxidant defences - is a condition associated with chronic-degenerative disease, such as cancer, metabolic and disease cardiovascular diseases (CVDs). Several studies have shown that diet and some of its components could influence the intensity of OS damage. The aim of this review was to critically examine some pieces of evidence from observational and intervention study in human beings to assess whether diet and its components can really modify OS in vivo. Furthermore, we tried to find out the possible mechanism behind this association. We considered all studies in MEDLINE which fitted with the following criteria: (1) adult subjects who were healthy or affected by metabolic disease and CVDs; (2) no food supplements, pillows, powder but only common foods and beverages and (3) OS assessment with well-known and validated in vivo biomarkers.