Oxidative stress has been described as an imbalance between oxidants substances (like free radicals) and antioxidants. Free radicals are species with one or more highly unstable unpaired electrons that cause them to react with other molecules generating new free radicals. The excess of highly reactive species as oxygen-derived species, cause damage to many biomolecules as DNA, lipids and proteins, with harmful consequences, and it is related with many diseases as cancer.

Environmental and lifestyle factors intervene in our oxidative balance. Environmental pollution, smoking, solar exposition or alcohol consumption can trigger oxidative stress. An insufficient intake of antioxidants or frequent practice of high-intensity physical exercise are also influential factors for high oxidative stress levels.