Antigenotoxic Effect of Kefir and Ayran Supernatants on Fecal Water-Induced DNA Damage in Human Colon Cells

Abstract

Fermented dairy products and their component bacteria have been shown to possess health-promoting functions in consumers and recently have been suggested to reduce the risk of colorectal cancer. Kefir and ayran are two popular fermented milk drinks that have their origins in the Caucasus region of Russia. The present study aimed to evaluate their potential anticancer properties in colon cells in vitro. The comet assay and transepithelial resistance assay were used to assess the effect of kefir and ayran supernatants on genotoxicity of fecal water samples and on intestinal tight junction integrity. Their antioxidant capacity was measured by trolox equivalent antioxidant capacity assay and compared with that of unfermented milk. The results showed that DNA damage induced by 2 of 4 fecal water samples was significantly decreased by kefir and ayran supernatants and with ayran the effect was dose-dependent. However no effect on intestinal tight junctions was observed. The supernatants of kefir and ayran contained high amounts of acetic and lactic acid but only a very small quantity of caproic and butyric acid, and they showed significantly greater antioxidant capacity than milk. These findings suggest kefir and ayran can reduce DNA damage, which might be due to their antioxidant capacities.

ACKNOWLEDGMENTS

This work was supported by the BRIDGE (British Degrees in Russia) project funded by the UK Department for Innovation, Universities, and Skills (DIUS), managed by the British Council and supported by the National Training Foundation for the benefit of the Russian and UK Higher Education Sectors. We would like to thank Dr. Francesca Fava of Department of Food Biosciences, University of Reading for providing us the fecal water samples.