Flavonoids as Antioxidants

Abstract

The oxidant reactions of free radicals and molecules with unpaired electrons are thought to contribute to many health problems. Antioxidants restrict the deleterious effects of oxidative stress. These effects can be direct (i.e., eliminating certain free radicals) or indirect (i.e., preventing radical formation). The body produces certain endogenous antioxidants (i.e., enzymes), which can be consumed in the diet. Some dietary antioxidants such as vitamin E are essential nutrients (the body cannot function normally without them). The diet also contains other components that are capable of antioxidant action. These belong to a class of food components known as phytochemicals. These compounds, such as flavonoids, are not required parts of the diet but may confer health benefits such as antioxidant action. It might be said that one can live without phytochemicals, but one might live better with them. If phytochemicals exert antioxidant actions in humans, the body's antioxidant capacity should diminish with a low-phytochemical diet. To a limited degree, this idea has been tested in a study conducted in our laboratory. ~Patients undergoing renal dialysis consumed one of three generified liquid formulas as the sole nutrition source for 3 weeks. Each formula contained essential nutrients in amounts generally considered adequate but did not contain major sources of phytochemicals. Nearly all subjects (12 = 20 for each of the three formulas) showed depressed plasma total antioxidant status (TAS) values. The decrease in TAS values could not be attributed to three major factors: vitamin E, vitamin C, or uric acid. p-Carotene was not a factor.