Submitted to: Annals Of Botany
Publication Type: Review Article
Publication Acceptance Date: January 26, 2005
Publication Date: March 22, 2005
Citation: Finley, J.W. 2005. Proposed criteria for assessing the efficacy of cancer reduction by plant foods enriched in carotenoids, glucosinolates, polyphenols and selenocompounds. Annals of Botany. 95:1075-96. Technical Abstract: The cancer-protective properties of vegetable consumption are most likely mediated through compounds that may have a variety of biological actions (bioactive compounds), including acting as direct or indirect antioxidants, turning on detoxification enzymes and regulating apoptosis and the cell cycle. The 'Functional Food' industry has produced and marketed many foods with enhanced concentrations of bioactive compounds but there are no universally accepted criteria for judging efficacy of the compounds, nor for determining the efficacy of the enriched foods for cancer chemoprevention. Carotenoids, glucosinolates, polyphenols and selenocompounds are families of bioactive compounds found in many common vegetables. Numerous studies have investigated the agricultural and human health implications of enriching foods with one or more of these compounds, but many critical gaps in our knowledge remain. This review proposes a decision-making process for determining whether there is reasonable evidence for chemoprotection by these compounds. It further proposes criteria to determine whether plant foods enriched in these compounds also are effective for reduction of cancer risk. Carotenoids and polyphenols are compounds for which the evidence is incomplete, and production of foods enriched in these compounds is premature. The evidence for cancer reduction by glucosinolates and lycopene is stronger, but the many factors that cause variability in the accumulation and chemical form of these compounds in plants presents an obstacle that must be solved before enhanced plant foods can be marketed. The evidence for cancer reduction by selenocompounds is strong and supported by clinical intervention studies, but the clinical study that is potentially the most convincing is still in progress and interim data are not yet available. Selenium-enriched plant foods have been produced and tested for cancer prevention, but the many factors that affect the amount and chemical form of Se in plants is still a barrier to production of Se-enriched foods. These gaps in understanding of bioactive compounds and their health benefits should not serve to reduce research interest, but should instead encourage plant and nutritional scientists to work together to develop strategies for improvement of health through food encourage plant and nutritional scientists to work together to develop strategies for improvement of health through food.