Consumption of Lactobacillus products and supplements containing viable lactic acid bacteria results in their establishment in the gastrointestinal tract. Their presence in the intestinal tract has been suggested to be prophylactic. They may reduce risk associated with dietary onset of carcinogenesis directly due to the reduction of procarcinogenic substances or indirectly due to the reduction in the level of enzymes that convert procarcinogens to carcinogens. In short-term studies, feeding as well as intraperitoneal administration of lactic acid bacteria suppress tumors implanted in rodents. The suppression is probably mediated by lactic acid bacteria through activation of host defense system. The activation of host defense system has been hypothesized to augment the immune system. Transient increase in the host immune defense system has been observed following feeding of cultured dairy products, but the biological significance of these changes has not yet been elucidated.
*Presented at the XIII International Symposium on Intestinal Microecology, Sept. 11–14, 1988, Porto Conte (Sassari) Sardinia, ITALY.