Epidemiological studies indicate that populations consuming high levels of plant derived foods have low incidence rates of various
cancers. Recent findings implicate a variety of
phytochemicals, including phenolics, in these anticancer properties. Both monophenolic and polyphenolic compounds from a large variety of plant foods, spices and beverages have been shown to inhibit or attenuate the initiation, progression and spread of
cancers in cells in vitro and in animals in vivo. The cellular mechanisms that phenolics modulate to elicit these anticancer effects are multi-faceted and include regulation of
growth factor-receptor interactions and cell signaling cascades, including
kinases and
transcription factors, that determine the expression of genes involved in cell cycle arrest, cell survival and apoptosis or programmed cell death. A major focus has been the inhibitory effects of phenolics on the stress-activated
NF-KB and
AP-1 signal cascades in
cancer cells which are regarded as major therapeutic targets. Phenolics can enhance the body's immune system to recognize and destroy
cancer cells as well as inhibiting the development of new blood vessels (angiogenesis) that is necessary for tumour growth. They also attenuate adhesiveness and invasiveness of
cancer cells thereby reducing their metastatic potential. Augmentation of the efficacy ofstandard chemo- and radiotherapeutic treatment regimes and the prevention of resistance to these agents is another important effect of plant phenolics that warrants further research. Plant phenolics appear to have both preventative and treatment potential in combating
cancer and warrant further, in-depth research. It is interesting that these effects of plant phenolics on
cancer inhibition resemble effects reported for specific
fatty acids (omega-3 PUFA,
conjugated linoleic acids). Although phenolic effects in cells in vitro and in animal models are generally positive, observations from the less numerous human interventions are less clear. This is surprising given the positive epidemiological data and may relate to mixed diets and synergistic interactions between compounds or the bioavailability of individual compounds. Much of the work in vitro with phenolic compounds has utilized concentrations higher than the amount that can be obtained from the diet suggesting a role of fortified, functional foods in
cancer suppression.