Traditional Japanese Fermented Food Natto Enhances NK Cell Activity in Intestine

Abstract

Fermented foods are widely accepted health products and are considered to be important components of the daily diet. The health-promoting effects of fermented foods may be attributed to both the beneficial effects of probiotics and the immunostimulatory functions of food components. In this study, we evaluated the immunostimulatory effects of fermented foods. Mice were orally administered fermented soybeans（natto）or yogurt twice a day for 7 consecutive days. One day after the last oral administration, mononuclear cells were isolated from the spleen and Peyerʼs patches（PP） , and were analyzed by flow cytometry to elucidate the frequency of natural killer（NK）cells. The results showed increased frequencies of NK cells in PP, but not spleen, of mice given natto or yogurt, as compared with mice given phosphate-buffered saline. These results suggest that ingestion of fermented foods, e.g., natto and yogurt, may stimulate innate immunity in the intestinal immune system.