The use of total antioxidant capacity as surrogate marker for food quality and its effect on health is to be discouraged

Attempts have been made to use non-compositional parameters, such as total antioxidant capacity (TAC), determined by assays such as oxygen radical absorbance capacity, ferric-reducing ability of plasma, and trolox-equivalent antioxidant capacity, as surrogate markers for food quality and for monitoring food-related changes in human plasma in dietary intervention studies. Increased TAC of plasma is often indiscriminately, and therefore incorrectly, interpreted as being favorable to human health. Whether or not dietary compounds may indeed exert health effects depends on factors other than mere presence in food or body fluids. Many phytochemicals, for example, are poorly absorbed and rapidly metabolized into molecules with altered physicochemical, and therefore biological, properties. Consequently, the use of TAC assays for the in vitro assessment of antioxidant quality of food, which often is employed as a marketing argument or for the assessment of the "wholesomeness" of food, is to be discouraged.