The effects of oral administration of milk and soy milk kefirs on tumor growth in tumor-bearing mice and the mucosal immunoglobulin A response in mice were studied. Oral administration of milk and soy milk kefirs to mice inoculated with sarcoma 180 tumor cells resulted in 64.8% and 70.9% inhibition of tumor growth, respectively, compared with controls. In addition, oral administration of the two kefir types induced apoptotic tumor cell lysis. Total immunoglobulin A levels for tissue extracts from the wall of the small intestine were also significantly higher for mice fed a milk kefir or a soy milk kefir regimen for 30 days. These results suggest that milk and soy milk kefirs may be considered among the more promising food components in terms of cancer prevention and enhancement of mucosal resistance to gastrointestinal infection.
