TABLE 1 Examples of Reactive Oxygen and Nitrogen Species

Name

Formula

Comments

Superoxide

O2-

An oxygen-centered radical. Has limited reactivity.

Hydroxyl

OH·

A highly reactive oxygen-centered radical. Very reactive indeed: Attacks all molecules in the human body.

Peroxyl, alkoxyl

RO2·, RO·

Oxygen-centered radicals formed (among other routes) during the breakdown of organic peroxides.

Oxides of nitrogen

NO·, NO2·

Nitric oxide (NO·) is formed in vivo from the amino acid L-arginine. Nitrogen dioxide (NO2·) is made when NO reacts with O2 and is found in polluted air and smoke from burning organic materials (e.g., cigarette smoke).

 

SOURCE: Adapted from Halliwell, 1996, with permission; © International Life Sciences Institute, Washington, D.C.

Measurement of Quantities in Foods

In order to meet the definition of a dietary antioxidant proposed here, the dietary intakes of the nutrient or food component must be able to be calculated from available national databases. These databases include the U.S. Department of Agriculture's National Nutrient Databank, the Canadian Nutrient File, and other databases that contain a nationally representative sample of foods commonly eaten in the United States or Canada and that report concentrations for the antioxidant of interest and others. It is recognized that limitations exist in the use of food composition databases to accurately estimate intakes.

Decreased Adverse Effects of Some ROS and RNS

In order to meet the definition of a dietary antioxidant proposed here, the nutrient or food component must decrease the adverse effects of some ROS and RNS (see Table 1 for examples of ROS and RNS). An explanation of the biochemical and physiological mechanisms of these adverse effects follows.

Role of ROS and RNS in Health and Disease

ROS and RNS are produced metabolically by the body. It has been estimated that about 1 to 3 percent of the oxygen we utilize goes to make ROS. In



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