The production of oxidative species (
free radicals) is very common in many types of
cancer cells. This oxidative stress has been associated with the carcinogenic process as it can damage cellular
proteins and
lipids and form
DNA adducts.
Antioxidants interact with these oxidative species and reduce their (pro)neoplastic activity. Therefore, intake of
antioxidants has been hypothesized to interfere with
carcinogenesis.
Chemoprevention by dietary or supplemental
antioxidants is a strategy which aims at reducing the incidence and prevalence of
cancer.
Antioxidants are present in plant food and considerable knowledge has been obtained on the mechanisms by which these
phytochemicals interact with the carcinogenic process. In general,
antioxidants prevent oxidative species to reach a sufficient intracellular level to promote
carcinogenesis. However, oxidative species do not only have a detrimental effect. At physiological levels they also confer prevention by inducing immunoresponses and apoptosis in order to remove the damaged cells. These beneficial actions are of extreme value for normal organ function, and it casts doubt on the use of supplemental
antioxidants. Indeed, from recent high-quality epidemiological studies the image emerges that supplemental
antioxidants may help to prevent
cancer only in diet-deficient populations or individuals. This paper aims at providing an overview on the knowledge about the most common (dietary)
antineoplastic chemoprevention agents and the clinical results obtained from epidemiological studies in this field.