All classical nutrient categories consist of bioactive dietary components, including carbohydrates, amino acids, fatty acids and structural lipids, minerals, and vitamins. In addition is an extensive list of non-nutrient components, particularly phytochemicals, which can have anticancer activity. Phytochemicals are components of a plant-based diet that possess substantial anticarcinogenic and antimu-tagenic properties.7 An estimated 25,000 different chemical compounds occur in fruits, vegetables, and other plants eaten by humans.8 They can encompass such diverse chemical classes as carotenoids, flavonoids, organosulfur compounds, isothiocyanates, indoles, monoterpenes, phenolic acids, and chlorophyll.9 Table 2.1 lists a sampling of bioactive compounds, most of which are discussed more comprehensively in subsequent chapters of this book.
Cancer-preventive properties of the macronutrient (carbohydrate, protein, fat, and fiber) and micronutrient (vitamin and mineral) components of diets have been the object of study for a number of years, and the National Cancer Institute (NCI) has sponsored a number of human intervention trials with individual vitamins and minerals.10 More recently, however, research efforts have extended to the non-nutritive phytochemicals. The NCI has determined that more than 35 plant-based foods and 1000 individual phytochemicals possess cancer-preventive activity in cell culture and animal models.7 Well-studied food sources and representative phytochemicals include garlic (diallyl sulfide), soybeans (genistein), turmeric (curcumin), tomatoes (lycopene), grapes (resveratrol), green tea (epigallocatechin-3-gallate [EGCG]), and cruciferous vegetables (such as broccoli, cabbage, and Brussels sprouts; indole-3-carbinol, sulforaphane).7 However, the repertoire of chemopreventive phytochemicals is vast, and foods, dietary supplements, and traditional herbal medicines with previously undocumented anticancer activities are continually being identified.
When discussing the activity of chemopreventive compounds derived from whole foods and dietary supplements, a couple of important principles should be recognized. First, whole foods contain a plethora of different constituents, each
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