Reactive oxygen species such as superoxide, peroxide and hydroxyl radicals are known to cause oxidative damage in both food systems and living systems. These species and their modification of cellular macromolecules have a significant pathological role in diseases such as cancer, hypertension, atherosclerosis and arthritis. There is considerable interest in the use of natural antioxidants to protect against free radical attack and to retard the progress of chronic diseases.

Mutagens and carcinogens in foods present a major concern to human health, with a high degree of correlation often being found between in vitro mutagenicity and in vivo carcinogenicity. Many mutagens act on the cell through its active metabolites or by generating free radicals. The use of antimutagens in the diet can help prevent or inhibit the development of human cancer and genetic diseases.

Soy beans are a good source of low-cost protein and have potential for lowering blood cholesterol and the incidence of heart disease and cancer. These attributes are associated with polyphenols, particularly isoflavone analogues such as genistein. Dietary genistein has been shown to enhance the activities of antioxidative enzymes and to demonstrate anticarcinogenic and antioxidative activities. Fermented milk such as kefir has also been associated with beneficial health effects including antimutagenicity, immune-potentiating activity, antitumour activity and antipathogenic activity.

A study by Liu et al.¹ evaluated the antimutagenic and antioxidative properties of milk-kefir and soymilk-kefir. Antimutagenicity was determined using the Salmonella mutagenicity assay, while the antioxidative activity was evaluated by determining the reducing power, radical scavenging, ferrous ion chelating and antioxidative enzymes. Both types of kefir showed significantly higher antimutagenic and antioxidative activities than milk or soymilk, suggesting they have potential as food components for preventing mutagenic and oxidative damage.
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¹ Je-Ruei Liu; Ming-Ju Chen; Chin-Wen Lin (2005). Antimutagenic and antioxidant properties of milk-kefir and soymilk-kefir. Journal of Agricultural and Food Chemistry 53 (7) 2467-2474.

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