Until the 1980's vitamins and minerals were considered important because they protected us against diseases caused by a deficiency of a given vitamin or mineral. The deficiency was clinically observable . This was followed by the realization that substances, other than vitamins and minerals, and which are present naturally in foods may also be protective. These substances are the phytochemicals. The exciting news about phytochemicals is their ability to inhibit carcinogenesis.
Phytochemicals are capable of halting that process at one or more of the stages.
They play a variety of roles such as antioxidants, suppressors of tumor growth, antimutagens, enzyme modulators, chemical inactivators, and free radical scavengers. Most of the evidence on the beneficial effects of phytochemicals comes from laboratory studies. This evidence suggests it may be possible that phytochemicals protect against human cancer but is not yet conclusive. In addition, under certain circumstances phytochemicals show the potential to promote cancer. More research needs to be done to confirm laboratory findings.