Lactic acid bacteria, which can be found in fermented foods such as sauerkraut or yoghurt, support our immune system and hence human health (cf. http://www.gesunde-bakterien.de/en/fermentation-bacteria-preserve-foods-and-nutrients-2/). Scientists at the University of Leipzig have now demonstrated the mechanisms behind this. They examined how lactic acid bacteria interact with specific receptors on the surface of cells in our body.
Humans and apes differ from most mammals in that they have not two, but three receptors known as hydroxycarboxylic acid (HCA) receptors. The third of these – HCA3 – is a protein which appears to be the link between lactic acid bacteria and the immune system. The scientists discovered that “a substance found in high concentrations in fermented foods like sauerkraut activates the HCA3 receptor, thus influencing the function of the human immune system,” as Dr. Claudia Stäubert, project head, is quoted in a university press release.
After eating sauerkraut, there were increased concentrations in the blood of a substance called D-phenyllactic acid which is released by lactic acid bacteria. This stimulated the HCA3 receptors which communicated to the immune system that foreign substances and energy had entered the body, which boosting the immune system.
That humans have this third HCA receptor is most likely thanks to our ancestors. The scientists in Leipzig assume that over the course of centuries during which fewer fresh fruits were available, people consumed fermented and fallen fruit. This may have lead to the development of HCA3. The precise way in which bacteria, receptors, and immune system communicate will be the subject of future research.
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