That's the message of new research from EMBL and Cambridge University's Patil group and collaborators, published in Nature Microbiology today. Members of the group study kefir, one of the world's oldest fermented food products and increasingly considered to be a 'superfood' with many purported health benefits, including improved digestion and lower blood pressure and blood glucose levels. After studying 15 kefir samples, the researchers discovered to their surprise that the dominant species of Lactobacillus bacteria found in kefir grains cannot survive on their own in milk -- the other key ingredient in kefir. However, when the species work together, feeding on each other's metabolites in the kefir culture, they each provide something another needs.