Propionate as a health-promoting microbial metabolite in the human gut

Propionate is a major microbial fermentation metabolite in the human gut with putative health effects that extend beyond the gut epithelium. Propionate is thought to lower lipogenesis, serum cholesterol levels, and carcinogenesis in other tissues. Steering microbial propionate production through diet could therefore be a potent strategy to increase health effects from microbial carbohydrate fermentation. The present review first discusses the two main propionate-production pathways and provides an extended gene-based list of microorganisms with the potential to produce propionate. Second, it evaluates the promising potential of arabinoxylan, polydextrose, and L-rhamnose to act as substrates to increase microbial propionate. Third, given the complexity of the gut microbiota, propionate production is approached from a microbial-ecological perspective that includes interaction processes such as cross-feeding mechanisms. Finally, it introduces the development of functional gene-based analytical tools to detect and characterize propionate-producing microorganisms in a complex community. The information in this review may be helpful for designing functional food strategies that aim to promote propionate-associated health benefits.