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Interest in antioxidants and antioxidant therapy has been growing during the last decade. Antioxidants are generally considered to have the capability to protect people from harmful effects of reactive oxygen and nitrogen species (RONSs), including free radicals (FR), when these are present in excessive amounts. RONS and free radicals perform a variety of useful biological functions in the body. Their excess is controlled by a natural antioxidant protection system in humans. This protection is provided at three levels: by simple molecules (such as cysteine, glutathione (GSH), uric acid, ubiquinol, etc.), medium-molecular weight, and high molecular weight compounds (enzymes, etc.). Under certain adverse conditions, this system does not manage to provide adequate protection and the RONSs and free radicals begin to damage vital DNA, proteins, and lipids. In such a case, antioxidant therapy, which includes antioxidant supplements and foods containing natural antioxidants, has been suggested to be of possible benefit. However, there are many unresolved issues related to the effective use of an antioxidant therapy: 1. A person should know the content of antioxidants in everyday food products and its relation to the storage time and processing methods used. 2. How many antioxidants should a person consume? It is known that at high concentrations some antioxidants become pro-oxidants. 3. Are the antioxidants consumed by a person bioavailable and, if so, to what extent; for some food products, bioavailability has already been determined but most foods have not been examined. 4. Many antioxidants are digested by intestinal microflora before they reach the systemic blood circulation. 5. Even those antioxidants that do reach the blood are often rapidly metabolized; the role of their metabolites is unclear; there is some evidence that certain metabolites are also antioxidants. 6. How long do antioxidants and their metabolites stay in the body; how are they distributed in different organs; and when are they excreted? In order to answer these questions, the pharmacokinetics of antioxidants should be studied. 7. The presence of oxidative stress, i.e., excess amounts of RONSs and free radicals, can be detected by various oxidative stress markers but, in order to see the whole picture, the actual concentrations of RONSs and free radicals should also be monitored. In vivo determination of RONSs and free radicals is almost never conducted. All these questions must be addressed in order to provide appropriate antioxidant therapy. This could be extremely important because it could be used to detect and even prevent diseases at early stages of development. [ABSTRACT FROM AUTHOR]

Oxidative stress, i.e. excessive content of reactionary, oxygen, and nitrogen compounds (ROAC), including free radicals, is one of the causes of various dangerous diseases as well as premature aging. The adverse effect of free radicals can be neutralized by antioxidants. In order to carry out antioxidant therapy, one needs to know the contents of antioxidants in food products. We have created the databank for the contents of antioxidants in 1,140 food products, beverages, etc. Apart from water-soluble antioxidants, fat-soluble antioxidants in dairy and fish products, cacao, chocolate, nuts etc. were determined for the first time using an amperometric method. [ABSTRACT FROM AUTHOR]