First International Symposium on the Role of Soy in Preventing and Treating Chronic Disease.
Diet, phytochemicals and cancer risk
ABSTRACT. The roots of medicine in our culture, and the practice of medicine in many parts of the world today, involve the prescription of specific foods (plants in particular) for a large number of illnesses. Historically, foods that have been ascribed healing properties included cruciferae, the allium family, celery, cucumber, endive, parsley, radish, and legumes. A review of the cohort and case-control studies of all cancer sites strongly suggests that consumption of the following vegetables and fruits is lower in those with cancer: raw and fresh vegetables, leafy green vegetables, cruciferae, carrots, broccoli, cabbage, lettuce, raw and fresh fruit, and citrus fruit. There are many biologically plausible reasons why consumption of vegetables and fruit might slow or prevent the appearance of cancer. These include the presence of potentially anticarcinogenic substances such as carotenoids, vitamin C, vitamin E, selenium, dietary fiber, dithiolthiones, isothiocyanates, indoles, phenols, protease inhibitors, allium compounds, plant sterols, limonene, and others, usefully called phytochemicals or bioactive compounds of plant origin. At almost every one of the stages of the cancer process, known phytochemicals can alter the likelihood of carcinogenesis, occasionally in a way that enhances risk, but usually in a favorable direction. For example, such substances as glucosinolates and indoles, isothiocyanates and thiocyanates, phenols, and coumarins can induce a multiplicity of solubilizing and (usually) inactivating enzymes; ascorbate and phenols block the formation of carcinogens such as nitrosamines; flavonoids and carotenoids can act as antioxidants, essentially disabling carcinogenic potential; lipid-soluble compounds such as carotenoids and sterols may alter membrane structure of integrity; some sulphur- containing compounds can suppress DNA- and protein synthesis; carotenoids suppress DNA-synthesis and enhance differentiation. Reduction of consumption of plant foods means reduced intake of a wide variety of substances that lower cancer risk. Vegetables and fruit contain the anticarcinogenic cocktail to which weare adapted. We abandon it at our peril.