Eating fruits and vegetables reduces risk of cancer by about 30%, however the active anticarcinogenic components of food remain to be determined. The well known oncogenic potential of oxidative stress have led to the use of antioxidants, contain in high proportions in fruits and vegetables, as cancer prevention. Numerous observational and interventional studies allowed to observe conflicting results. For example, in two major trials (CARET and ABTC) the risk of lung cancer was increased rather than reduced by beta-carotene supplements in smokers. Meta-analyses analyzing studies about supplementation in primary or tertiary prevention showed no benefit on overall survival regardless of tumor type studied or anti-oxidant evaluated. Those assessing the effect of non medical antioxidants taken during the anticancer treatments (chemotherapy or radiotherapy) indicate that if the objective of reducing side effects can sometimes be achieved, the risk of tumor progression and increasing mortality must not be disregarded. Because of the absence of formal effectiveness proof and potential risk of mortality, prophylactic supplementation with antioxidants can not be recommended. Varied and balanced diet of fruits and vegetables remains the best nutritional attitude to prevent the risk of cancer and should be promoted at all levels.