Safety considerations in the use of nonviable microbial cells as health-promoting agents in food and dietary supplements

This review explores the safety issues related to the utilization of nonviable microbial cells in food and dietary supplements. It addresses potential risks associated with their consumption, drawing insights from probiotic research. Four categories of risks are outlined: • Antibiotic resistance genes, which may persist even in nonviable cells; • The presence of viable microbial cells, which can result from incomplete inactivation or contamination; • Bioactive microbial cell components, which can influence immune responses; • Detrimental enzymatic activities, relevant particularly when considering novel inactivation methods. Human intervention trials involving nonviable microbes demonstrate a high safety profile, especially for established probiotics. Nonetheless, caution is warranted in vulnerable individuals. Furthermore, the use of nonviable microorganisms provides an opportunity to explore microbial species not commonly used as probiotics, referred to as ‘next-generation probiotics.’ As our understanding of nonviable microbes deepens, their potential benefits will likely lead to increased interest in various biotic product applications.