Phytochemicals: nutraceuticals and human health

Phytochemicals, as plant components with discrete bio-activities towards animal biochemistry and metabolism are being widely examined for their ability to provide health benefits. It is important to establish the scientific rationale to defend their use in foods, as potential nutritionally active ingredients. Phytochemicals could provide health benefits as: (1) substrates for biochemical reactions; (2) cofactors of enzymatic reactions; (3) inhibitors of enzymatic reactions; (4) absorbents/sequestrants that bind to and eliminate undesirable constituents in the intestine; (5) ligands that agonize or antagonize cell surface or intracellular receptors; (6) scavengers of reactive or toxic chemicals; (7) compounds that enhance the absorption and or stability of essential nutrients; (8) selective growth factors for beneficial gastrointestinal bacteria; (9) fermentation substrates for beneficial oral, gastric or intestinal bacteria; and (10) selective inhibitors of deleterious intestinal bacteria. Such phytochemicals include terpenoids, phenolics, alkaloids and fiber. Research supporting beneficial roles for phytochemicals against cancers, coronary heart disease, diabetes, high blood pressure, inflammation, microbial, viral and parasitic infections, psychotic diseases, spasmodic conditions, ulcers, etc is based on chemical mechanisms using in vitro and cell culture systems, various disease states in animals and epidemiology of humans. However, it must be emphasized that a distinction needs to be drawn between the types of information that can be obtained from studies in vitro, in animals and in humans. Mechanisms of action must certainly be established in vitro; however, the efficacy of these same ingredients with their mechanisms of action, must also be demonstrated in vivo. The rapid growth in the use of phytochemicals in nutraceutical and functional foods requires that the food and pharmaceutical industries face new challenges: in addressing worldwide public concern over the efficacy and safety of supplements and foods claimed to be health-promoting; in government regulations related to safety, labeling and health claims for products that contain phytochemicals; in the manufacturing of foods with different qualities and stabilities; and in marketing issues, particularly as they relate to consumers' recognizing added value. (C) 2000 Society of Chemical Industry.