Sauerkraut bacteria signal the immune system

Fermented foods are known to be good for you, and good old-fashioned sauerkraut made by fermenting cabbage with lactic acid bacteria is no exception. Claudia Stäubert and colleagues at Leipzig University were investigating hydroxycarboxylic acid (HCA) receptors when they discovered that a molecule produced by sauerkraut bacteria, D-phenyllactic acid, binds strongly to one of those receptors, HCA₃ (PLOS Genet. 2019, DOI: 10.1371/journal.pgen.1008145). The team fed volunteers sauerkraut and found high levels of D-phenyllactic acid in their blood and urine, high enough to activate the volunteers’ immune cells. This observation suggests that sauerkraut plays a physiological role as well as a nutritional one, a finding that Thue Schwartz of the University of Copenhagen says is “truly interesting.”

HCA₃ is found in only humans and apes. By using bioinformatics, Stäubert’s team showed that the gene for HCA₃ entered the ape genome around the same time as did the gene for alcohol dehydrogenase, which helps us break down toxic alcohols. These findings make a “compelling case” that a change in diet modified the molecular biology of our primate ancestors, says Steven Benner of the Foundation for Applied Molecular Evolution.